cosmic vision - space science for europe 2015-2025

Contact: ESA Publications Divisionc/o ESTEC, PO Box 299, 2200 AG Noordwijk, The NetherlandsTel. (31) 71 565 3400 - Fax (31) 71 565 5433

BR-247

Spa

ce S

cien

ce f

or

Euro

pe

2015

-202

5Cosmic VisionCosmic Vision

COVER5 11/3/05 3:56 PM

BR-247October 2005

Cosmic VisionSpace Science

for Europe 2015-2025

LAYOUT3 11/3/05 4:32 PM Page 1

BR-247 ‘Cosmic Vision’

Prepared by: Giovanni Bignami, Peter Cargill, Bernard

Schutz and Catherine Turon on behalf of

the Science advisory structure of ESA, and

by the Executive of the Science

Directorate, supported by Nigel Calder

Published by: ESA Publications Division, ESTEC, PO Box

299, 2200 AG Noordwijk, The Netherlands

Editor/Design: Andrew Wilson

Layout: Jules Perel

Copyright: © 2005 European Space Agency

ISSN: 0250-1589

ISBN: 92-9092-489-6

Price: EUR 10

Printed in The Netherlands

Cover

A fresco painted 1509-1511 by Raphael (1483-1520) in the

Vatican (Stanza della Segnatura, Palazzi Pontifici) perhaps

depicts the embodiment of Astronomy.

(Copyright Photo SCALA, Florence)

Replacing the original astronomical globe is Mars viewed by

the High Resolution Stereo Camera (ESA/DLR/FU Berlin,

G. Neukum) carried by the ESA Mars Express spacecraft,

merging into an image (G. Hasinger, Astrophysikalisches

Institute, Potsdam) of X-ray sources in the Lockman Hole made

using the Newton X-ray Observatory spacecraft.

Chapter divider

Artist's impression of a quasar located in a primieval galaxy a

few hundred million years after the Big Bang.

(ESA/W. Freudling, ST-ECF/ESO)


32

Cosmic Vision: Space Science for Europe 2015-2025

Contents

Foreword 4

Executive Summary 6

Introduction: Why Space Science Needs Long-Term Planning 10

1. What are the Conditions for Planet Formation 18and the Emergence of Life?

2. How does the Solar System Work? 28

3. What are the Fundamental Physical Laws of the Universe? 38

4. How did the Universe Originate and What is it Made of? 52

5. Technology Requirements 62

6. Proposed Strategies and Their Implementation 82

7. Conclusions 92

Afterword 96

Annex 1: Authors and Memberships 100

Annex 2: Submitted Themes for Cosmic Vision 2015-2025 102

Acronyms 110


‘Science is shaped by ignorance’ says DavidGross, 2004 Nobel Prize in Physics. Spacescience is no exception: by going after ourknowledge gaps (or ignorance chasms) inthe Universe around us, we focus onquestions that then both direct andmotivate us. Identifying these questions hasbeen the starting point of the current soul-searching exercise, which occupied a fullyear in the life of Europe’s space scientists.Watching them go into action and feelingtheir response has been both an intenseexperience and a unique privilege.

Today’s science rests on the contribution ofevery citizen. In our case, this means askingeach European to invest about €1 per yearin two equally noble purposes: to be a littleless ignorant about our Universe and togive a much-needed boost to Europe’sspace industry. (Of this yearly Euro, ourEuropean taxpayers should know that80 cents will go to industry, in the form oftechnology-intensive contracts).

Throughout our Cosmic Vision 2015-2025exercise, it was apparent that scientists wereconscious of the responsibilities they carrytowards Europe’s taxpayers as much astowards their own future community. Theywere, and are, also conscious of the burdenthey carry: the opinions of a communitythat has more then doubled in the last twodecades deserves the respect of Europe’sdecision-makers. We know they have todeal with the numerous factors that haveintolerably squeezed our meagre yearly €1for space science.

Fore

wor

d


With Cosmic Vision 2015-2025, we showthat we do not complain – we getorganised.

After the questions, came not the answers,of course. Rather, as you will see, priority-based science strategies were identified, aswell as roadmaps for the development ofthe technological tools necessary for suchstrategies.

Just as cognac, schnapps or grappa distilthe spirit out of a variety of fruits, fromgrapes to plums (and the occasionalpotato…), the pages that follow capture thespirit of Europe’s space scientists. Ourdistillation process adhered to a time-honoured tradition that has been followedby ESA over the 30 years since its creation. Ithas been the responsibility of ESA’sDirectorate of Science advisory structure, i.e.the Astronomy Working Group, theFundamental Physics Advisory Group andthe Solar System Working Group, toevaluate and discuss the ‘dictionnaire desidées reçues’ from the community.Ultimately, it was the Space ScienceAdvisory Committee (SSAC) that tookresponsibility for the conception andwriting of Cosmic Vision 2015-2025, withthe fundamental support of the ScienceDirectorate Executive.

The SSAC, the Working Groups and indeedthe whole community are keenly aware ofthe foreseeable costs of space missions aswell as of ESA’s Directorate of Sciencecurrent (and foreseeable) budget. We knowthat not all of the ideas given here will berealised. We are not having intoxicated

dreams: with maturity, we are puttingforward a realistic set of scientific strategiesout of which the implementation ofmissions must logically follow.

A feeling of ‘schicksalsgemeinshaft’, thatspecial sharing of a common destiny,permeated the SSAC and rendered ourworking together both effective andpleasant, albeit at times strenuous. To ESA,to Europe’s decision-makers and, above all,to the next generation of space scientists,we present our work. Our confidence indoing so stems from the vast intellectualcontribution received as an input: we areprofoundly grateful for it.

Giovanni F. BignamiChairman, SSAC

54



Ten to twenty years from now, a successionof clever new spacecraft will need to beready to fly in ESA’s continuing ScienceProgramme, now called Cosmic Vision. Theywill tackle some of the big scientificquestions that are posed in this document.Such long-term planning has alreadyproved its worth in the Horizon 2000 (1984)and Horizon 2000 Plus (1994-1995) plans.They enabled Europe’s scientific,technological and industrial teams tocommit themselves with confidence to themany years of hard work that it takes toconceive and execute space projects ofworld-beating quality.

In that highly successful tradition, CosmicVision 2015-2025 aims at furtheringEurope’s achievements in space science forthe benefit of all mankind. The plan is basedon a massive response by the scientificcommunity to ESA’s call for themes, issuedin April 2004. A total of 151 novel ideas(listed in Annex 2) were submitted, morethan twice as many as for the equivalentexercise in 1984.

ESA’s scientific advisory committees andworking groups then made a preliminaryselection of themes, which were discussedin a workshop in Paris in September 2004,attended by nearly 400 members of thescientific community. After an iteration withthe Science Programme Committee (SPC)and its national delegations, ESA’s SpaceScience Advisory Committee (SSAC)prepared the present plan with the keenassistance of ESA’s Directorate of Science.The SSAC is made up of scientists chosenfor their scientific standing and who are

Exec

utiv

e Su

mm

ary


expected to represent the views of theEuropean science community as a wholerather than any particular national interest.A further encounter with the wider spacescience community occurred at asymposium in Noordwijk in April 2005. On5 May 2005, in Helsinki, the SPC saw a draftof the report and endorsed the approach.

Science in the 21st Century is seekinganswers to profound questions about ourexistence, and our survival in a tumultuouscosmos. What is even more important isthe rate of increase of our knowledge. Wecan now pose questions that seemedbeyond our reach less that a generationago. Many of the answers can be soughtand found only with space projects of ever-increasing ingenuity. ESA is not alone inrecognising the scientific challenges, and itembraces collaboration with otheragencies whenever that is opportune.However, Europe has made its mostdistinctive contributions to space scienceby giving its own scientists everyopportunity to prioritise their goals.

Cosmic Vision 2015-2025 addresses fourmain questions that are high on theagenda of research across Europe (and,indeed, worldwide) concerning theUniverse and our place in it:

— what are the conditions for planetformation and the emergence of life?

— how does the Solar System work? — what are the fundamental physical

laws of the Universe? — how did the Universe originate and

what is it made of?

Chapters 1 to 4 spell out the opportunitiesunder these headings, and identify specificaspects of each general theme that arejudged to be especially ripe forinvestigation by new space tools in theperiod 2015-2025. Chapter 5 reviews thetechnology that will have to be developed.Finally, this planning on behalf of thescientific community and aerospaceindustry takes into account the ScienceDirectorate’s preliminary reckoning of thepractical constraints of technology. InProposed Strategies and TheirImplementation (Chapter 6), the outcome ofthese deliberations is summarised in fourtables that correspond to our four keyquestions. A compacted version of thosetables is shown overpage.

The team preparing Cosmic Vision 2015-2025 has subdivided the four mainquestions by selecting areas where majorprogress can be expected in the next twodecades. Under each of the resultingsub-headings, one, two or three appropriatespace techniques (or tools) are nominated.It is here that technical progress in the next10 years is required, and the targets finallychosen and the progress made willdetermine what we can confidently doscientifically maybe 20 years from now. Insome cases, the same technique or toolappears in more than one context, thanksto its cross-disciplinary character.

The breadth of the investigationsrepresented in the table is enormous. Theyrange from the poles of the Sun to the birthof the Universe, from gigantic cosmicstructures to sub-atomic particles. Also

76



remarkable is the way that very differenttechniques converge on the same question,whether it is the origin of life or thefundamental physics of the cosmos thatmake our existence possible.

The space tools in the table should be seenas candidate concepts for missions, ratherthan as cut-and-dried requests forindividual funding. Still less are they firmpromises to the scientific community. Toomany projects have been proposed forthem all to be affordable in the 2015-2025timeframe. Exactly how much can beaccomplished will depend on the Level ofResources of the Science programme, butalso, in part, on what internationalcollaborations can be arranged.Competition between the candidateconcepts will be unavoidable.

In any case, some flexibility must remain inthe space science programme, to allow forunforeseen opportunities or difficulties,whether in the science or in the technology.The readiness of the technology – oftenhighly innovative – will be a factor in theselection and sequencing of the eventualmissions.

It is foreseen that ESA’s Directorate ofScience will issue a succession of Calls forMission Proposals to implement the plan.Following a successful tradition,international collaboration withnon-European space agencies, includingNASA, will be a key ingredient in theimplementation of this programme. WithinEurope, interactions with national spaceprogrammes, and also with the European

Southern Observatory (ESO) and theEuropean Organisation for NuclearResearch (CERN), will be explored in full.Within ESA itself, strong coordination withthe Earth Observation Programme, theAurora Exploration Programme and otherprogrammes will give an overall boost tothe scientific and technological activitiesproposed here.

Thanks to the blend of ambition andrealism in our plan, Europe’s aerospaceindustry has not only expressed a stronginterest in the ideas, but also pledged itssupport for the future of science in space.With every new space technique or toolenvisaged here, Europe’s technologicalcompetence will grow.

Above all, Cosmic Vision 2015-2025 shouldappeal to the new European Space Council,because it fosters the European Union’svisible presence in space activities fromwhich many strategic, industrial, culturaland educational benefits will flow. The planis an expression of trust in Europe’s politicalwill, from the large and multi-faceted spacescience community in universities andinstitutes throughout the continent. Thescientists who gladly contributed their bestideas and expertise to our study nowconfidently expect support for the timelyimplementation of this excitingprogramme.


98


Candidate Projects in strategic sequences(question by question)

Near-Infrared NullingInterferometer

Mars Landers + Mars Sample Return

(with Aurora Programme)

Far-Infrared Observatory

Solar Polar Orbiter

Terrestrial Planet Astrometric Surveyor

Europa Landers

Earth Magnetospheric Swarm

Solar Polar Orbiter

Jupiter ExplorationProgramme including Europa

Orbiter and Jupiter probes

Near-Earth Object Sample Return

Interstellar Heliopause Probe

Fundamental PhysicsExplorer Programme

Large-Aperture X-ray Observatory

Deep Space Gravity Probe

Gravitational Wave Cosmic Surveyor

Space Detector for Ultra-High-Energy Cosmic Rays

Large-Aperture X-ray Observatory

Wide-Field Optical-InfraredImager

All-sky Cosmic MicrowaveBackground Polarisation

Mapper

Far-Infrared Observatory

Gravitational Wave Cosmic Surveyor

Gamma-Ray Imager

Scientific Questionssubdivided into topics where important progress can be expected in the

Cosmic Vision 2015-2025 timeframe

1. What are the conditions for planet formation and the emergence of life?

1.1 From gas and dust to stars and planets

Map the birth of stars and planets by peering into the highly obscuredcocoons where they form

1.2 From exo-planets to biomarkers

Search for planets around stars other than the Sun, looking for biomarkers in their atmospheres, and image them

1.3 Life and habitability in the Solar System

Explore in situ the surface and subsurface of the solid bodies in the SolarSystem most likely to host – or have hosted – life

Explore the environmental conditions that makes life possible

2. How does the Solar System work?

2.1 From the Sun to the edge of the Solar System

Study the plasma and magnetic field environment around the Earth andaround Jupiter, over the Sun’s poles, and out to the heliopause where the

solar wind meets the interstellar medium

2.2 The giant planets and their environments

In situ studies of Jupiter, its atmosphere, internal structure and satellites

2.3 Asteroids and other small bodies

Obtain direct laboratory information by analysing samples from aNear-Earth Object

3. What are the fundamental physical laws of the Universe?

3.1 Explore the limits of contemporary physics

Use stable and weightless environment of space to search for tiny deviationsfrom the standard model of fundamental interactions

3.2 The gravitational wave Universe

Make a key step toward detecting the gravitational radiation backgroundgenerated at the Big Bang

3.3 Matter under extreme conditions

Probe gravity theory in the very strong field environment of black holes andother compact objects, and the state of matter at supra-nuclear energies in

neutron stars

4. How did the Universe originate and what is it made of?

4.1 The early Universe

Define the physical processes that led to the inflationary phase in the earlyUniverse, during which a drastic expansion supposedly took place. Investigatethe nature and origin of the Dark Energy that is accelerating the expansion of

the Universe

4.2 The Universe taking shape

Find the very first gravitationally-bound structures that were assembled inthe Universe – precursors to today’s galaxies, groups and clusters of galaxies

– and trace their evolution to the current epoch

4.3 The evolving violent Universe

Trace the formation and evolution of the supermassive black holes at galaxycentres – in relation to galaxy and star formation – and trace the life cycles of

matter in the Universe along its history


One memorable morning, early in 2005, adiscovery machine built in Europe madethe most distant landing ever attempted onanother world. The European SpaceAgency’s probe Huygens, crammed withscientific instruments, descended to thesurface of Titan, a mysterious moon ofSaturn. It revealed icy landscapes with riverbasins carved by liquid hydrocarbons, in akind of world previously unknown toscience. Huygens made headline newsworldwide, but not without an element ofsurprise that Europe should have pulled offsuch an impressive feat.

The very name of the mission, Cassini-Huygens, celebrated the Europeanastronomers who explored Saturn and itsrings and moons in the 17th Century. Thebasic technologies – propulsion by rockets,descent by parachute and communicationby radio – were all pioneered in Europe. Yetmodern Europe is suspected, rightly orwrongly, of being politically lukewarmtowards space science, because it spendsmuch less on it than does NASA.

To conceive and execute the Huygensmission took more than 20 years. Two spacescientists in France and Germany formallyproposed an ESA probe to Titan in 1982. Sixyears later, the joint NASA/ESA/ASI Cassini-Huygens mission was approved. Afterintensive work by Europe’s space scientistsand engineers, the completed Huygensprobe was attached to Cassini in good timefor the launch in 1997. Continuingtransatlantic collaboration throughout thelong flight to Saturn ensured the probe’sperfect delivery to Titan. Cassini’s big radio

Intr

oduc

tion

LAYOUT3 11/3/05 4:32 PM Page 10

dish, contributed by the Italian spaceagency, ASI, received the signals fromHuygens and relayed them to the Earth. Thesuccess of this mission is, first and above all,due to the interest and perseverance of theproposing scientists, and to the highlycreative and ingenious solutions workedout by industry to build an engine that haspushed the human frontiers on spaceexploration. None of this – a developmenttime of 17 years, preceded by a longpreparatory effort – would have beenpossible if ESA had not had a long-rangespace science plan.

Scientists, technologists, national fundingagencies, space industry and internationalpartners, all relied very heavily on theexistence of ESA’s long-term plan to buildconfidence in the success of a project thattook two decades to develop. Huygens is byno means an exception in the length ofdevelopment of a space science mission,which typically takes decades to return itsfinal science. The Horizon 2000 plan, whichplanned the Cassini-Huygens mission, wasprepared in 1984; Horizon 2000 Plus in1994-1995. The present Cosmic Vision 2015-2025 document is the logical continuationinto the next decade of the ESA scienceplanning cycles.

The year of 2005 is especially apt for takingstock of the new science performed fromspace on the continent of Ptolemy, Tycho,Kepler, Galileo, Newton and Einstein.A century after the ‘annus mirabilis’ of thetheory of relativity, photoelectric effect andBrownian motion, we celebrate 30 years ofactivity of the European Space Agency, itself

born on a previous decade of work by theEuropean Space Research Organisation(ESRO). We, the European space scientists,are proud to have again given a newcontribution to mankind in its quest forunderstanding the Universe. After about4000 years of naked-eye astronomy, Galileoinitiated 400 years of astronomy with ever-more powerful telescopes, followed by40 years of space astronomy. In each ofthese historical periods, astronomers havegathered more information about theUniverse than in the previous one, in aspectacular example of the acceleration ofscience.

Why do astronomy? Astronomy, theunderstanding of our Universe andmankind’s place in the Universe, is themother of all science. Lack of interest inbasic science, in addition to the devastatingeconomic effects it has – no basic sciencemeans no applications – is always thesymptom of profound diseases of any society.

Why look at the heavens from space?Most of our information on celestial objectscomes through the electromagneticradiation that planets, stars and galaxiesemit throughout the spectrum. Theyobviously do not care that on our planetonly a small (frequency) window, the one towhich our eyes became adapted, penetratesthe atmosphere. Placing telescopes in orbithas provided astronomers with an immenseleap in their powers of observation. Therecent Nobel Prize to Riccardo Giacconi forthe development of X-ray astronomy is butone example of the recognition of such awidening of horizons.

1110

Why Space Science Needs

Long-Term Planning

LAYOUT3 11/3/05 4:32 PM Page 11

There is another dimension of research inspace that is more akin to traditionalexploration: exploration in situ. Europe iscurrently present on many planets in theSolar System, including the Moon, Mars, theSaturn/Titan system, Venus and, tomorrow,Mercury. Europe is thus acquiring data onall the major solid-body atmospheres in theSolar System: Venus, Mars and Titan. Thepotential benefits for understanding theevolution and fate of the fourth solid-bodyatmosphere in the Solar System, that of ourEarth, are apparent. Planetology helps us toput in context the particular planet onwhich we happen to live. On the otherhand, participating in missions closing in onthe Sun has given us a new view of our ownstar, which ultimately controls our lives.

There is more to space astronomy besidesthe electromagnetic spectrum and in situexploration. We also receive informationfrom the Universe through essentiallyuntapped channels, such as gravitationalwaves – another of Einstein’s predictions –that have so far only been indirectlyobserved. Through them, we expect toimprove our understanding of a variety ofphenomena, such as merging neutron stars,forming gigantic black holes in the centresof Galaxies, and the very first instants of theexplosion that gave birth to the Universe.

Finally, the ‘corpuscular’ channel has beenexploited from the very first cosmic-rayexperiments aboard satellites for samplingthe origin and composition of nucleisynthesised in stars, as well as forunderstanding their importance in theenergy balance of our Galaxy, and their

significance for interplanetary space andindeed our Earth. To these now-traditionalparticle astronomy studies, new physicsdimensions could be added that addressexotic species or energy levels so farunexplored.

In this global panorama of science advances,rendered possible by access to space, Europehas contributed, through ESA, complementedby additional national efforts, in a major way.Through creativity, organisation anddetermination, Europe has achievedleadership in a number of research areassince ESA’s foundation. However, ESA and itsMember States have achieved successes inspace science that are disproportionate totheir relatively small budgets. They comefrom pursuing difficult and highly originalprojects in an unwavering fashion over manyyears. Like Aesop’s tortoise competing withthe hare, Europe gets there in the end –whether to the sludgy surface of Titan or intoorbit with the world’s most sensitive X-rayand gamma-ray telescopes, XMM-Newtonand Integral.

Huygens revealed a worldpreviously unknown toscience: first colour view ofTitan’s surface. (ESA/NASA/JPL/Univ. Arizona)

LAYOUT3 11/3/05 4:32 PM Page 12

After proving its competence in spaceastronomy with COS-B for gamma-rays(1975) and Exosat for X-rays (1983), thescientific mission through which ESA ‘cameof age’ was probably Giotto (1985-1986).Witness the breathtaking movie of Giotto’sapproach to within less than 600 km ofcomet Halley, much closer than any otherspace agency dared to go. The Rosettamission, launched in 2004, will land on acomet in 2014, reinforcing the leadingposition achieved by Giotto.

In 1989, Hipparcos was launched, a uniquesatellite that gave unprecedented and, asyet, unmatched accuracy in measuring thepositions and motions of stars within arange of hundreds of light-years in ourGalaxy and, for the first time, solved thediscrepancy between the age of the oldeststars in the Milky Way and the expansionage of the Universe. This mission will befollowed in 2012 by Gaia, a much morepowerful satellite, able to map one billionstars in six dimensions and decipher thehistory of the entire Galaxy. Space

astrometry, by now an establishedEuropean specialty, has given us directaccess to the distance ladder, whose stepsmeasure our Universe.

Both Giotto and Hipparcos were projectsthat NASA in principle might have donebut did not. The scientific and political willcame from Europe. Yet willpower on behalf of individual science projects wasnot enough. By the early 1980s, Europe’sscientific institutes, aerospace companiesand governments all realised that to create and preserve talented teams, aswell as to be reliable partners ininternational collaborations, ESA neededlong-term commitments in planning andfunding.

Horizon 2000 and Horizon 2000 PlusAfter continent-wide brainstorming in1983-1984, Horizon 2000 replaced theprevious à la carte style of missionselection by an appetising table d’hôte.There was judicious provision for updatingthe programme with missions still to bechosen. Despite some delays anddescoping owing to budgetaryconstraints, the promises of Horizon 2000will be broadly fulfilled when theastronomical missions Herschel and Planckset off into space in 2007. The second stepin this decadal series is Horizon 2000 Plus,including highly promising missions suchas Gaia, BepiColombo, JWST, LISA and SolarOrbiter. A brief résumé of the most strikingresults obtained or still expected fromthese two long-term designs is givenbelow.

1312


Gaia will decipher the history of the entire Galaxy.

LAYOUT3 11/3/05 4:32 PM Page 13

In November 1995, the Infrared SpaceObservatory gave us views of the ‘cold’Universe and its chemical history that hadnever previously been seen, discovering,most importantly, ‘water, water everywhere’.Herschel will follow up this success bygoing to longer wavelengths and exploringcolder regions, where more complexmolecules are formed. Meanwhile, its launchcompanion, Planck, will explore ourUniverse and its origin at even longerwavelengths. In a sense, Planck will obtainhigh-resolution images of the Universe ininfancy, and from there precisemeasurements of its basic constituents.

The study of our magnetosphere, themagnetic bubble that travels with our Earthand protects it from the outbursts of ourstar and from the steady flux of cosmic rays,is another area where ESA is making themost important contribution, following up aseries of earlier small missions. The key ideawas that of flying four identical spacecraftin formation, allowing for the first timesynchronous study in three-dimensions ofparticles and fields in our magnetosphere.Here, ESA had to fight bad luck, because thefirst Cluster mission was lost in the failure ofthe debut Ariane-5 launch in 1996.However, the decision was quickly taken

and acted upon to fly a replica of themission. This took place in 2000, and Clusterhas continued to fly with success. In 2003-2004, through an ESA-Chinese collaboration,the mission was enriched by two Chinesesatellites (‘Double Star’) carrying manyEuropean instruments.

X-ray astronomy attracted the earliestobservations in space science, and is a fieldwhere Europe in general and ESA inparticular have been active since thebeginning. After the positive outcome of theExosat mission in the early 1980s, which flewa first generation of X-ray optics, the XMM-Newton observatory was launched in 1999.Still fully operational, it features novel X-rayoptics of unprecedented throughput and isopening up high-sensitivity X-rayspectroscopy for many classes of celestialobjects, including black holes and neutronstars, as well as large reservoirs of ionisedmatter trapped by the gravity of celestialobjects. ESA’s tradition in gamma-rayastronomy, dating back 30 years, is beingextended with the Integral observatory(2002). This unique mission combines high-resolution imaging and spectroscopy in thecrucial, yet poorly explored, wavelengthregion where most nuclear radiation isemitted by the most energetic objects in thelocal Universe.

In planetary research, competition withNASA has mostly given way to cooperation,such as through the imaginative Cassini-Huygens mission. However, Mars Express, aEuropean mission, and certainly thecheapest mission ever sent to Mars, has beenproducing first-class scientific data, despite

Mars Express has found what appears to be a dust-covered frozen sea near the Martian equator.(ESA/DLR/FU Berlin; G. Neukum)

LAYOUT3 11/3/05 4:32 PM Page 14

the loss of Beagle-2, with breathtakingthree-dimensional high-resolution images,and the discovery of water and methane,the chemical prerequisite/markers ofpossible biotic activity. The launch of thesister mission Venus Express in 2005promises comparably high achievements atthe cloud-masked planet, which stillpresents many puzzles despite 40 years ofinvestigation by American and Sovietspacecraft. Closer to the Sun and even morebaffling is the planet Mercury, the target forone of the main projects ofHorizon 2000 Plus: BepiColombo. Named forthe Italian scientist who improved NASA’sreconnaissance of Mercury in 1974-1975with the gravity-assist method, this missionis now a joint European-Japanese project.

In other fields, ESA shares its scienceleadership with NASA, through partnershipand cooperation. The first major jointsuccess was the longest lived (so far)cooperative mission, the International

Ultraviolet Explorer (IUE, 1978), anastronomy mission with NASA and theUnited Kingdom. The Hubble SpaceTelescope, still operating, has opened a newobservational era for astronomy, and similarastronomical and cosmologicalbreakthroughs are expected from itssuccessor, the James Webb Space Telescope,also a joint ESA/NASA/CSA venture. Ulysses(1990), still operating, has been exploringthe heliosphere, the bubble of particle, gas,radiation and magnetic field travelling withour Sun through interstellar space. Butperhaps the best example ever of asuccessful cooperative mission is given bySOHO, still operational after a decade inorbit. Thanks to SOHO, a number ofmysteries and questions about the innerand outer structures of our Sun have beenanswered. Another challenge is LISA (LaserInterferometer Space Antenna), a joint ESA-NASA project which, by searching forgravitational waves, will open a newwindow on the Universe. On LISA Pathfinder

1514


Thanks to SOHO, solarmysteries are beingsolved. (ESA/NASA– SOHO/LASCO)

LAYOUT3 11/3/05 4:32 PM Page 15

(2009), ESA will test European and Americancontributions to the amazing technologyrequired for this project.

At the time of writing, ESA is flying a total of17 scientific and other satellites. Thanks tothe two long-term programmes for science,Horizon 2000 and Horizon 2000 Plus, thereare now in orbit 15 ESA scientific spacecraft,of which nine are directly operated by ESA.They have earned high respect fromscientists all around the world, who like tobe involved in the missions. Most of themedia coverage of ESA’s activities concernsthese scientific spacecraft, which is notsurprising because they far outnumber thesatellites in orbit for other ESA programmes.The quality of engineering achievable witha long-term plan is part of the explanationfor this remarkable number of missions inprogress. Europe’s scientific, technologicaland industrial teams were able to committhemselves with confidence to the manyyears of hard work that it takes to conceiveand execute world-beating space projectsto high technical standards. As a result,several missions are still harvestingscientific knowledge long after they wereexpected to finish.

Cosmic Vision 2015-2025Such is the story so far. The individualsuccesses of this long-term planning ofESA’s space science programmenevertheless conceal the general problemthat even a tortoise needs nourishment.Many of the fantastic missions describedabove were decided before the Level ofResources of the Science Programme began

to decrease. Despite tireless trimming ofmission costs – by technical finesse, by newmanagement practices and by recruitinginternational partners to share the expense– some consequences of the erosion ofESA’s space science budget during the past10 years are now plain to see.

One was the first-ever cancellation of anapproved ESA science mission. Eddingtonwas meant to follow up SOHO’s success instudying the Sun’s interior by its rhythmicvariations in brightness, and apply the sameseismic method to the stars. And had it notbeen cancelled, Eddington would havechecked out half a million stars for thepossible presence of Earth-sized planetspassing in front of their parent stars. Painfulsurgery also eliminated Europe’s MercuryLander intended to fly on BepiColombo.Some other missions have been deferred toan extent that endangers their expectedperformances, strains the loyalty of thescientific and industrial teams, puts thepersonal careers of young researchers atrisk, and is actually wasteful of money.

At the time of writing, celebrations areunder way for the 30th anniversary of ESA.ESA is a different organisation from what itwas 30 years ago and it reflects a differentenvironment. The evolution of our spacescience community deserves specialattention. It is the one on which ESA’sScience Programme ‘insists’ and which isserved by the programme. It represents thefuture for Europe, not only in terms of newideas and work but also for the Programmegovernance it constantly expresses throughESA’s advisory bodies.

LAYOUT3 11/3/05 4:32 PM Page 16

In time-honoured fashion, the communitywas called upon to express its new ideas inApril 2004, and did so with unprecedentedenthusiasm. The community was patentlyconscious of the responsibility it had to taketo build its own future through respondingto the need for space science in a newEurope. A total of 151 novel ideas (listed inAnnex 2) were submitted, more than twice asmany as for the equivalent exercise in 1984-1985. The number of participants perproposal has also significantly increased,together covering the whole space sciencecommunity of Europe. In some countries,such as Spain, the increase has beendramatic. Decision- and policy-makers aretoday confronted with an obviousengagement of an important sector of oursociety.

Cosmic Vision 2015-2025 tries to give justiceto all such aspirations. It aims boldly atfurthering Europe’s achievements in spacescience, for the benefit of all mankind. Aswith its predecessors, the plan has beencreated ‘by the scientists, for science andindustry’. ESA’s scientific advisory committeesand working groups (Annex 1) made apreliminary selection of themes, which werediscussed in an open workshop in Paris inSeptember 2004, attended by almost 400members of the scientific and industrialcommunities. After an iteration with theScience Programme Committee (SPC) and itsnational delegations, and a second openSymposium in April 2005, ESA’s multinationalSpace Science Advisory Committee (SSAC)prepared the present plan, with the keenassistance of ESA’s Directorate of Science,and presented it to the SPC in May 2005.

Cosmic Vision 2015-2025 addresses fourmain questions that are high on the agendaof research across Europe (and, indeed,worldwide) concerning the Universe andour place in it:

— what are the conditions for planetformation and the emergence of life?

— how does the Solar System work? — what are the fundamental physical laws

of the Universe? — how did the Universe originate and

what is it made of?

Chapters 1 to 4 spell out the opportunitiesunder these headings, and identify specificaspects of each general theme that arejudged to be especially ripe forinvestigation by space projects in theperiod 2015-2025. Chapter 5 reviews thetechnologies that will have to bedeveloped. In Chapter 6, ProposedStrategies and Their Implementation, theplanning by the scientists, for scientists andindustry is matched to the ScienceDirectorate’s reckoning of the constraints oftechnology and cost. Potential space toolsto address each of our four key questionsare summarised in four tables. A possiblescheme for their orderly implementationduring the next 20 years is described. Thisenvisages that the Science ProgrammeExecutive may wish to make a Call forMission Proposals early in 2006 for the firstpost-2015 projects. Finally, Chapter 7,Conclusions, reflects on the interfacebetween scientific discovery and politicalwillpower, as Europe faces the opportunitiesand challenges of space exploration in the21st Century.

1716


LAYOUT3 11/3/05 4:32 PM Page 17

A question that fascinates mankind is whatwas the succession of events after the BigBang and the formation of stars andgalaxies, and under which conditions, thatled to the origin of life on Earth? Equallycaptivating is the question of whether lifeexists elsewhere in the Universe and, if so, inwhat forms, on which kind of planets andlinked to which type of stars. As we areworking on theories to explain the physicalprocesses by which life might appear andevolve on a planet, we are in the somewhatpeculiar situation in which only one planethosting life is presently known. No othersign of life has ever been detected either onthe other planets or satellites in the SolarSystem or elsewhere in the Universe. For thetime being, life on Earth provides a solitaryexample to guide our physical, chemical andbiological investigations.

A decade ago, when the Solar System wasthe only planetary system known, theorieswere developed to account for theformation and evolution of such a system.Since then, the discovery of more than 160planets orbiting stars beyond the Sun hastaught us the limit of such an approach. Theformation of many of these systems, withgiant planets ( ‘hot Jupiters’) orbiting closelyto the stars, seemed impossible within theframework of the theories accepted as littleas 10 years ago. Based on this salutaryexample, we can only wonder what scientificand philosophical revolution the discoveryof life on another planet will provoke.

We are now at a unique moment in humanhistory. For the first time since the dawn ofphilosophical and scientific thought, it is

Chap

ter1

LAYOUT3 11/3/05 4:32 PM Page 18

within our grasp to answer, rigorously andquantitatively, two fundamental questions:

— are there other forms of life in the SolarSystem and did they have anindependent origin from those thatdeveloped on Earth?

— are there other planets orbiting otherstars similar to our own Earth, andcould they harbour life?

Spelling out these themes in more specificscientific terms leads to the followingquestions:

— what are the conditions for stars toform and where do they form?

— how do they evolve as a function oftheir interstellar environment?

— do stars hosting planets have specialcharacteristics?

— what are the conditions for planets toform around stars?

— what are the different kinds of planetsorbiting stars? What is their massrange? Are there planets similar tothose of the Solar System?

— which planets are surrounded byatmospheres? What are thecharacteristics of these atmospheres?

— what are the conditions for life (of anyform) to appear on these planets?

— for life to survive and evolve, what arethe environmental conditions –geological, hydrological, atmosphericand climatic, and the stellar magneticand radiation environment?

For the first time, we are able to buildinstruments that allow us to investigate

directly how unique the Earth is andwhether or not we are alone in theUniverse. Discovering Earth’s sisters andpossibly life is the first step in thefundamental quest of understanding whatsuccession of events led to the emergenceand survival of life on Earth. For this, weneed to know how, where and when starsform from gas and dust and how, whereand when planets emerge from thisprocess. This is certainly one of the mostimportant scientific goals that ESA andEurope could set themselves.

1.1 From gas and dust to stars andplanets

The atoms from which the presentgenerations of stars and planets wereformed went through a succession ofviolent processes from the very early times,when the Universe began and the firstgeneration of stars formed. Most objects wesee today are made from the ashes of starsthat no longer exist. Indeed, this also appliesto mankind, as we are literally stardust. Thestars that produced the carbon we have inour bodies, and the oxygen we breathe,were formed, evolved and died long ago.Much information comes both fromground-based and space observatories onthe way that stars evolve throughout theirlives. Data on how stars die are being andwill be obtained by X-ray and gamma-rayspace observatories. Conversely, the waythat stars and planetary systems formremains much less well known.

Many sorts of observations at manydifferent wavelengths are required in order

1918

What are the Conditions for Planet

Formation and the Emergence of Life?

LAYOUT3 11/3/05 4:32 PM Page 19

to characterise the large variety of starsfound in a galaxy and all their possibleevolutionary states. ESA continues to play aleading role in the understanding of manyaspects of the life and death of stars. Itspioneering astrometric satellite, Hipparcos,provided unprecedented information onthe luminosities, motions and ages of starsin the solar neighbourhood. Gaia, now inpreparation, will build on this expertise andextend the measurements to the wholeMilky Way Galaxy, bringing within itsastrometric reach even the faintest and/orthe most rapidly evolving stars. In additionto luminosities, motions and ages of stars allover the Galaxy, the spectrophotometricinstrument aboard Gaia will providedetailed chemical information on theatmospheres of the brightest stars amongthe one billion objects it will observe.

While our understanding of stellar evolutionis making giant leaps forward, we still lack acomprehensive theory explaining why andhow stars form from interstellar matter and,apparently quite often, planetary systemswith them. The formation of planets has tobe considered in the wider context of starformation and circumstellar disc evolution.

Magnetic fields and turbulence are ofteninvoked as playing a key role in the birthprocess. The large diversity of orbitalcharacteristics among the exo-planetspoints to the importance of planet-disc andplanet-planet interactions. These can lead tosurprising consequences, such as large-scale inward migration of giant planetsand/or pumping of the orbital eccentricity,which then raises questions about the long-term stability of these systems. The problemis therefore essentially to establish whichbasic characteristics of the star-formationprocess determine the bulk properties ofthe planetary system that eventuallyemerges, several tens of millions of yearslater.

The star- and planet-formation processesrequire a multi-wavelength approach,mostly from near-infrared to millimetrewavelengths. A large part of thiswavelength range is absorbed by Earth’satmosphere, and observable only fromspace. With ESA’s Infrared SpaceObservatory (ISO) mission completed, theHerschel far-infrared observatory inpreparation, and ESA’s plannedparticipation in NASA’s James Webb SpaceTelescope (JWST), and with ESO’s ground-based facilities including the joint Europe-US Atacama Large Millimeter Array (ALMA)project, the European star formationcommunity is in a very strong position.

However, a key window in theelectromagnetic spectrum has yet to befully opened to make further definitiveprogress in this field: the far-infrared. Thesewavelengths are best suited to observe and

Comparative characteristics of exoplanets and SolarSystem planets. The exoplanets discovered so far are verydifferent from Solar System planets. Masses and semi-major axis are plotted (blue dots) for 160 exoplanets (TheExtrasolar Planets Encyclopaedia, J. Schneider) and eightSolar System planets (red dots); Pluto lies beyond theframe of the figure). (W. Benz, Univ. Bern, Swizerland)

LAYOUT3 11/3/05 4:33 PM Page 20

study the dusty regions where stars andplanets are forming, for three main reasons:the peak of the spectral energy distributionemitted by these regions is located at thesewavelengths, key water lines are found inthis spectral range, and the dust extinctionis minimal. Since Earth’s atmosphere isopaque at these wavelengths, this spectralwindow can be opened only from space.Even with a 3.5 m telescope, Herschel is notsensitive enough to resolve proto-stars.Hence a new-generation far-infraredobservatory space mission is required. Aspatial resolution of the order of 0.01 arcsecwill be needed to resolve the proto-starsand their associated discs in the neareststar-forming regions, together with high-and low-resolution spectroscopycapabilities in order to characterise lineemission and dust mineralogy.

1.2 From exo-planets to biomarkersThe first detection of a planet orbiting asolar-type star, achieved by a Europeanteam, occurred only 10 years ago. Many ofthe 160-odd planets found as of today haveunexpected orbital characteristics. These

discoveries have sparked a large number ofobservational efforts, all over the world, tofind more of these objects, as well astheoretical studies aimed at explaining theircharacteristics. The European astronomycommunity has played a particularlyimportant role in this endeavour, buildingon the synergy between ground-based andspace projects. A joint ESA-ESO workinggroup is now dedicated to this cooperation.

To understand the origin of the SolarSystem in general and of the Earth inparticular, it is essential to place ourplanetary system into the overall context ofplanetary system formation. To guide thetheory, a complete census of all the planetsfrom the largest to the smallest out todistances as large as possible is required.This can be achieved by making use of avariety of detection techniques, rangingfrom the high-precision measurement ofradial velocities, high-accuracy astrometryto detect the tiny reflex motion of the starin the plane of the sky, and photometry tomeasure the changes of brightness during atransit or during a gravitational lensingevent.

2120


Hubble Space Telescope’spanoramic view of a star-forming region in theLarge Magellanic Cloud(LMC), a neighbouringgalaxy only 160 000 light-years from Earth. With itshigh resolution, theHubble is able to viewdetails of star formation,showing glowing gas, darkdust clouds and young, hotstars. However, far-IRwavelengths would open akey window to observeand study the dustyregions where stars andplanets are forming.(NASA/ESA; HubbleHeritage Team(AURA/STScI)/HEIC)

LAYOUT3 11/3/05 4:33 PM Page 21

A large and complete sample will tell uswhich stars are most likely to host whichkinds of planets. It will, for example, allowquantification of the influence of thechemical characteristics of host stars (ismetallicity a key factor for planetaryformation?), and of their position andmotion with respect to the galactic planeand the global rotation of the Galaxy. Thestatistical analysis of the planets’ orbitalparameters and mass will unravelcorrelations which might point towards thekey physical mechanisms involved in theformation and evolution of these systems.Most likely, we will also discover planetswith masses and temperatures compatiblewith the formation of an atmosphere andthe presence of liquid water, i.e. planets inthe ‘habitable zone’.

All the discoveries of planets have so farcome from ground-based telescopes,although space-based instrumentation hasalready provided some extraordinaryinsights, such as Hubble Space Telescopeobservations of a photometric transit of oneexo-planet in front of its mother star, andthe evaporation of the atmosphere ofanother exo-planet. The situation is about tochange with the prospective detection ofplanets of nearly the same size as the Earthby the French-ESA Corot mission and laterby NASA’s Kepler.

Only the extremely stable environment ofspace observatories will bring thepossibility of high-precision photometryand astrometry. A major census of the giantplanets by ESA’s Gaia astrometric missionwill deliver systematic insights into the

frequency of giant planets in the Galaxy. Itwill thereby set important constraintsconcerning the properties of the host stars,and their locations in the Galaxy, that favourthe formation of planets. In addition, sincethe presence and location of one or severalgiant planets may severely affect theformation of smaller planets in a system,Gaia will provide important information onthe likelihood of finding Earth-like planetsorbiting their stars in the habitable zone.

The coming decade will be devoted to thestatistical exploration of planetarypopulations and to the understanding ofthe best conditions for planetary systemformation. Thereafter, within the 2015-2025timeframe, new observational techniqueswill allow us to separate the photonscoming from the planets from thosestemming from the host star, and will openan entirely new era of direct detection ofexoplanets and planetary imaging andspectroscopy. This will represent a majorstep forward in our ability to studyexo-planets, during which the temperature,

Detecting thebiomarkers in thespectrum of anEarth-like planet isa difficult problem.

Spectrum of the Earth, taken by the OMEGA visibleand infrared mineralogical mapping spectrometerof Mars Express on 3 July 2003. Since the Earth filledabout one OMEGA pixel from the 8 million kmdistance, the spectrum corresponds to the entireilluminated crescent, dominated by the PacificOcean. It covers the 0.35-5.15 µm visible and near-IRdomain, with spectral sampling varying from 4 nmto 20 nm. Several molecules were easily identified inthis region. (ESA/IAS Orsay)

LAYOUT3 11/3/05 4:33 PM Page 22

chemical composition and othercharacteristics of the atmospheres of thesebodies can be measured. With thesecapabilities, we will also have the means tosearch in the spectrum for possible markersof biological activities.

Only a space observatory will have theability to distinguish the light from Earth-like planets and to perform the low-resolution spectroscopy of theiratmospheres needed to characterise theirphysical and chemical properties. The targetsample would include about 200 stars inthe solar neighbourhood. Follow-upspectroscopy covering the molecular bandsof CO2, H2O, O3 and CH4, typical tracers ofthe Earth spectrum, will deepen ourunderstanding of Earth-like planets ingeneral, and may lead to the identificationof unique biomarkers. The search for life onother planets will enable us to place life asit exists today on Earth in the context ofplanetary and biological evolution andsurvival.

To make it possible, a major technicalhurdle has to be overcome: the high

brightness ratio between the star and theplanet. Pioneering work by ESA andEuropean laboratories is leading to thedevelopment of advanced technologybased on optical interferometry to achievedestructive interferences reducing, ornulling, the star’s light but leaving theplanet’s unmodified. A near-infrarednulling interferometer operating in thewavelength range 6-20 µm would providethe tool necessary to achieve theseobjectives. Based on the technology andexpertise already being developed, andimplemented around 2015, it would makeEurope a pioneer in this field and guaranteeits continuing leadership in exo-planetresearch.

On a longer timescale, a complete censusof all Earth-sized planets within 100 pc ofthe Sun would be highly desirable.Building on Gaia’s expected contributionon larger planets, this could be achievedwith a high-precision terrestrial planetastrometric surveyor. Eventually, thedirect detection of such planets followedby high-resolution spectroscopy with alarge telescope at infrared, visible and

2322


Earth observed byVoyager-1 on 14 February1990 from 42.6 AU,showing a crescent of only0.12 pixel. (NASA)

LAYOUT3 11/3/05 4:33 PM Page 23

ultraviolet wavelengths, and ultimately byspatially-resolved imaging, will mark thecoming-of-age of yet another entirely newfield of astronomy: comparativeexo-planetology.

1.3 Life and habitability in the SolarSystem

The quest for evidence of a second,independent genesis of life in the SolarSystem must begin with an understandingof what makes a planet habitable and howthe habitable conditions change, eitherimproving or degrading with time. Forinstance, the environmental conditions onthe Earth today are not the same as whenlife first arose on this planet. The earlyEarth, with its oxygen-free atmosphere,high ultraviolet radiation, hightemperatures and slightly acidic waters,could not support the highly evolved lifeforms so familiar to us. However, life couldnot have arisen on a planet with theenvironmental conditions that exist onEarth today.

We can define the basic habitableconditions for life, as we know it. For life toappear, a planet needs liquid water, a

source of carbon, a source of energy and asource of nutrients including nitrogen (N),phosphorus (P), sulphur (S), magnesium(Mg), potassium (K), calcium (Ca), sodium(Na) and iron (Fe). For life to survive, thenutrients need to be renewed and this canonly be done by active geologicalprocesses, such as recycling of the crust bysome form of tectonic activity. For life toevolve, however, the environmentalconditions on a planet need to evolve aswell. On Earth, the phenomenon of habitatevolution is related to the parallel processesof geological evolution and the interactionof life processes with the planet, leadingmost conspicuously to the appearance offree oxygen and a protective ozone layer inthe atmosphere.

A major problem on Earth is that platetectonics have eliminated all of the first500 million years of rock history andseverely altered the next 500 million years,so that the crucial first billion years whenlife arose and took a foothold is barelyrecorded. This gap in our knowledge can befilled by studying other planets that did notdevelop plate tectonics and still have arecord of the early environmentalconditions. Mars is an ideal goal. Althoughthe present conditions at the surface of theplanet are not conducive to the long-termsustenance of life, Mars had an early historythat was similar to that of the early Earthand conditions that were suitable for theappearance of life. A major question is: howdid continued evolution of the planet affectthe habitable environment and whathappened to the planet to make its surfaceuninhabitable today?

Layers of water ice and dust in Mars’ north polar cap,observed by Mars Express. The cliffs are almost 2 km high,and the dark material could be volcanic ash. (ESA/DLR/FUBerlin; G. Neukum)

LAYOUT3 11/3/05 4:33 PM Page 24

Spacecraft going to Mars can thereforeaddress basic questions regarding thehabitability of the Solar System, such as:

— what were the conditions during theearliest period in the history of theterrestrial planets when the planetsbecame habitable and when lifeappeared, at least on Earth?

— did geological evolution on Mars affectthe habitable environment, and whathappened to the planet to make itssurface apparently uninhabitable today?

— was there ever, or is there still, life onMars?

The spacecraft will need to investigate thestructure, geochemistry and mineralogy ofrocks in various geological locations on Marsin order to identify their origin andgeological history. More generally, they needto gather information about the mechanismsthat controlled the evolution of the Martianenvironment and the history of water onMars. It is essential to place any in situmeasurements in context; for example, didthe rocks form in a liquid waterenvironment? Such investigations shouldalso include science packages to search forevidence of extinct or extant life.

Additional geophysical investigations of thedeep and crustal structure of the planet are

needed to understand its present state andactivity. Measurements of climaticconditions are also required, to trace theirevolution and the conditions of habitatsback in time. Access to specific, selectedlocations on Mars, including rough and highterrain, and to the subsurface, will beessential for investigating many differentgeological and environmental settings andthus maximising the chances of detectingtraces of life, if any.

These goals may require the developmentof new technologies for Mars landers, suchas capable rovers, precision landing anddeep drilling. Orbiting spacecraft could beused to carry out remote sensing of theplanet, its atmosphere and climate, and itsplasma-magnetic environment, while actingas a relay satellite. Monitoring of thepresent environment is also needed tounderstand the present condition of thehabitat and also in preparation of futuremanned missions.

Ultimately a high-priority goal, whichshould be achievable in the 2015-2025timeframe, is a Mars sample return project,bringing back samples from selected sitesalready studied by landers. While in situmeasurements at multiple locations willprovide invaluable information, there aresome investigations that require terrestrial

2524


Europa is a high-prioritytarget in the search forhabitability in the SolarSystem. (NASA/Galileo)

LAYOUT3 11/3/05 4:33 PM Page 25

laboratory analyses, including isotopicmeasurements, microfossil identification andage dating.

Jupiter’s moon Europa, which possesses aninterior ocean, also has a high priority in thesearch for habitability in the Solar System. Itis important to determine Europa’s internalstructure and especially its internal heatsources. Analysis of the composition of theocean and icy crust is of paramountimportance for determining the availabilityof nutrients. The plasma and radiationenvironment around Jupiter and itsinteraction with Europa would also provideimportant information regarding thesurvivability of any life throughout themoon’s history. These science goals could beachieved by a dedicated Europa orbiterand/or lander. While highly desirable, aEuropa lander may not be technologicallyfeasible within 2015-2025.

Ferocious particle radiation at Europa, whichvisiting spacecraft will have to endure, would

make life quite impossible on its surface.This illustrates another important aspect ofhabitability, namely the magnetic couplingbetween the central star and its planetarysystem. The Earth’s habitability, in particular,is maintained by a slowly evolving Sun thatgives almost constant illumination whilescreening us from energetic particlescoming from supernovae in the Galaxy. Thesolar wind, expanding from the hot solarcorona throughout the heliosphere, carriesturbulent magnetic fields out to the edge ofthe Solar System, which drastically reducethe flux of cosmic rays. To characterisecompletely the conditions needed tosustain life, especially in an evolved form,we must therefore understand the solarmagnetic system, its variability, its outburstsin large solar eruptions and the interactionsbetween the heliosphere and the planets’magnetospheres and atmospheres. A SolarPolar Orbiter would provide much-neededinsight into the structure of the Sun’smagnetic field, especially by observing itfrom above the poles (Section 2.1).

LAYOUT3 11/3/05 4:33 PM Page 26

2726


Toolkit for Theme 1

1. What are the conditions for planet formation and theemergence of life?

Place the Solar System into the overall context of planetaryformation, aiming at comparative planetology.

1.1 From gas and dust to stars and planets

Map the birth of stars and planets by peering into thehighly obscured cocoons where they form

Investigate star-formation areas, proto-stars and proto-planetarydiscs and find out what kinds of host stars, in which locations inthe Galaxy, are the most favourable to the formation of planets

Investigate the conditions for star formation and evolution

1.2 From exo-planets to biomarkers

Search for planets around stars other than the Sun, lookingfor biomarkers in their atmospheres, and image them

Direct detection of Earth-like planets, with physical andchemical characterisation of their atmospheres for theidentification of unique biomarkers

Systematic census of terrestrial planets

Ultimate goal: image terrestrial planets with a large opticalinterferometer

1.3 Life and habitability in the Solar System

Explore in situ the surface and subsurface of solid bodies inthe Solar System most likely to host – or have hosted – life

Mars is ideally suited to address key scientific questions ofhabitability. Europa is the other priority for studying internalstructure, composition of ocean and icy crust and radiationenvironment around Jupiter

Environmental conditions for the appearance and evolution oflife include not only geological processes, the presence of waterand favourable climatic and atmospheric conditions, but alsothe magnetic and radiation environment commanded by theSun’s magnetic field

Tools

Far-infrared observatorywith high spatial and lowto high spectral resolution

Near-infrared nullinginterferometer with high

spatial resolution and low-resolution spectroscopy

Terrestrial planetastrometric surveyor

Mars exploration withlanders and sample return

Europa orbiter and/orlander in Jupiter

Exploration Programme(JEP)

Solar polar orbiter to chart the Sun’s

magnetic field in 3-D

LAYOUT3 11/3/05 4:33 PM Page 27

The search for the origins of life discussedin Chapter 1 must begin in our own SolarSystem. Understanding how the Sunbehaves over a range of timescales, how theplanets can be shielded from its radiativeand plasma output, why the nine SolarSystem planets are so different from oneanother, and what the small bodies such ascomets and asteroids can tell us about ourorigins – these are only a few aspects of thequestion. The generic circumstances underwhich planets are habitable are unknown,but must depend on the radiative outputand magnetic activity of the neighbouringstar, on the behaviour of the spaceenvironment surrounding the planets, onthe material from which the planetsoriginally accreted, and so on.

The exploration of the Solar System alsoencompasses many other scientificquestions of fundamental importance,beyond the origins of life. Why do the Sunand other stars generate magnetic fields?Why do these fields result in a high-temperature corona and a solar (or stellar)wind? How do planetary atmospheres andmagnetospheres respond to the interactionwith the solar wind? Why do planets andmoons have such a variety of atmospheresand surfaces? What determines thepresence of water on planets, now or in thepast? What are comets and asteroids madefrom and what does this tell us about theorigin of the Solar System?

European scientists and ESA have taken ona leading role in the exploration of our SolarSystem over the past 40 years, addressingthese questions. The achievements are

Chap

ter2

LAYOUT3 11/3/05 4:33 PM Page 28

multiple and impressive, and will remain sofor the next decade.

The Sun and the heliosphere have beenexplored by the Ulysses and Solar andHeliospheric Observatory (SOHO) missions.Ulysses has produced the firstcharacterisation of the ‘three-dimensionalSun’ through its pioneering flight over thesolar poles, demonstrating the verysignificant differences between theminimum and maximum of the activitycycle, as well as revealing very large gaps inour understanding of how magnetic fieldsand particles fill the heliosphere. SOHO haspioneered techniques for looking below thesolar surface, by helioseismology, revealinga complex range of mass motions thattransport energy and magnetic fieldthrough the solar convection zone. Thecoronal imaging instruments aboard SOHOhave revealed a new, dynamic, multi-thermal solar corona that has forcedscientists to rethink their ideas of how thecorona is heated. Finally, SOHO hasconvincingly demonstrated the genericcausal link between massive solar eruptionsand disturbances in the Earth’s spaceenvironment, dominated by coronal massejections. In the future, ESA’s Solar Orbitermission will examine the Sun from vantagepoints unique in two respects: from close in,at about one-fifth of the distance from theSun to the Earth, and from up to about 30°out of the ecliptic plane.

The Earth’s space environment wasexplored by HEOS-1 and -2 back in the daysof the European Space ResearchOrganisation that preceded ESA, and more

recently by the pioneering and innovativefour-spacecraft Cluster mission. Cluster is aunique enterprise. For the first time in themagnetosphere of the Earth, it has beenpossible to obtain accurate measurementsof the motion of the plasmas found there,as well as of the shape of the boundariesthat lie between the terrestrial and solarmagnetic fields. It is now clear that the Sunand solar wind exercise a very strongdegree of control over the magnetosphere.Cluster, along with the Double Star mission,carried out in collaboration with theChinese Space Agency, has also revealed forthe first time the complex hierarchy ofspatial and temporal scales that govern thisinteraction. European expertise in this fieldalso extends to studies of themagnetosphere of Saturn, throughextensive participation in the NASA-ESA-ASICassini-Huygens mission, with anabundance of data already from the Cassiniorbiter. The space plasma community islooking forward with great excitement toexploring the enigmatic magnetosphere ofthe planet Mercury as part of the ESA-JAXABepiColombo mission. Among its uniquefeatures, compared with other magneticplanets, Mercury’s magnetosphere has noionosphere.

Europe took the lead in the exploration ofcomets with the remarkable encounter in1986 of the Giotto spacecraft with cometHalley. This bold mission showed for thefirst time the actual shape of the cometarynucleus, the complex processes by whichmaterial sublimates from the nucleus toform in particular the tail, and the extensiveinteraction of cometary material with the

2928

How Does the Solar System

Work?

LAYOUT3 11/3/05 4:33 PM Page 29

solar wind that extends millions of km fromthe comet. The European cometarycommunity is looking forward to the arrivalof the Rosetta spacecraft and lander atcomet Churyumov-Gerasimenko in 2014.

Mars Express is currently mapping theMartian surface and monitoring its climatesystem with new instruments that havealready provided major discoveries. Theunprecedented colour, stereo and spectralimages, as well as the multi-wavelengthspectral observations, are revealing newaspects of Martian geology andclimatology, including recent volcanism,glaciers, water ice reservoir, and allowingthe identification of evaporitic minerals thatformed in the presence of liquid water.Furthermore, traces of methane in theatmosphere have been detected. TheEuropean planetary science communityawaits the first ESA mission to Venus, VenusExpress, to be launched later in 2005. Thiscross-disciplinary mission will undoubtedlymake important breakthroughs concerningthe surface and atmosphere of Venus, aswell as its interaction with the solar wind.

The spectacular results from Huygens haverevealed Saturn’s moon Titan to be a

fascinating place. Many features can be saidto resemble those found on Earth, such asdrainage channels and oceans, but otherfeatures are strikingly different: thedominance of hydrocarbons in theatmosphere and on the surface, rocks madeof dirty ice, and methane rain! Even at thisearly stage in the analysis of the data, it isclear that these results will have anenormous influence on planetary science.

The future of Solar System science inEurope is bright for the next decade. We willexplore the innermost planets (Mercury,Venus and Mars) in extraordinary detailwith the BepiColombo, Venus Express andMars Express missions. We will continue tolook at the Sun with the ESA-NASA SOHOand the JAXA-ESA Solar-B spacecraft, andeventually with Solar Orbiter, as well asmaking contributions to the internationalSTEREO mission. The very pleasant windfallof an extended Cluster mission will enableEurope to continue to set the internationalstandard in multi-point measurements ofthe magnetosphere, complemented byinvestigations of magnetospheres atMercury and Saturn. But what comes afterthat? This is the question we now address.

2.1 From the Sun to the edge of theSolar System

The Sun dominates the Solar System. Itsradiation provides the means to sustain life,but its continuous and occasionally violentactivity provides the means to destroy it.Both are critically important areas to bestudied. Only in the Solar System can weestablish the ‘zero-order truths’ concerning

Mars Express in 2005 revealed water ice in a 35 km-diameter crater on the Vastitas Borealis plain, whichcovers much of Mars’ far northern latitudes.(ESA/DLR/FU Berlin; G. Neukum)

LAYOUT3 11/3/05 4:33 PM Page 30

the Sun, its all-important magnetic field andthe interaction of the solar wind with theplanetary environments, which can then beextended to planetary systems elsewhere inthe Universe.

The varying magnetic field of the Sun isdirectly responsible for changes in the solarultraviolet and X-ray emission, and is alsoclosely related to the physics of long-termsolar cycles and their possible forcing rolein climatic variations. It is responsible forthe solar activity that leads to the solarwind plasma interacting with the planetaryenvironments. The solar magnetic field iscontinuously generated and destroyed ontimescales ranging from fractions of asecond to decades, and it fills theheliosphere, a volume of space that extendsto at least 10 billion km from the Sun. Thesetopics will remain major scientificchallenges in the Cosmic Vision 2015-2025timeframe.

The structure of the global magnetic field atthe Sun’s visible surface is not known andits determination will require observationsfrom above the poles. To understand thefield’s origin, through the dynamo processbelieved to operate at the base of theconvection region, calls for the mapping ofthe global 3-D subsurface flows, especiallyat the poles, and imaging of the subsurfacestructure through local and globalhelioseismology. In this way, one can obtaina picture of how the field is transportedimmediately below the surface, and howthat relates to what emerges through thesurface. The primary requirement is for asolar polar orbiter.

The magnetic field in the Sun’s coronadrives solar activity on timescales of hoursto weeks to years to centuries, through thelevel of ultraviolet and X-ray emissions fromthe corona. However, the critically importanttechniques to measure that field are onlynow being developed. These include thestudy of important emission lines in theinfrared and by spectropolarimetry atshorter wavelengths using the Hanle effect,whereby scattering of emission-lineradiation in the presence of a magnetic fieldleads to polarised light. At present, some ofthese techniques are being pioneered usingground-based instrumentation, but makingsuch observations from space is likely toprove highly desirable owing to the broaderpossible wavelength coverage, especially inthe ultraviolet domain.

The expansion of the Sun’s atmosphere fillsthe heliosphere with the plasma andmagnetic field that are collectively knownas the solar wind. In this medium, processesthat are generic to all of astrophysics(heating, the acceleration of particles andturbulence) can be studied withcomparative ease. These processes alsodictate how the Sun’s magnetic fieldinteracts with planetary environments.Some planets (Mercury, Earth and the gasgiants) have magnetic fields that providepartial shielding. Mars has a thin

3130


The structure of theSun’s global magneticfield at the visiblesurface remainsunknown.

LAYOUT3 11/3/05 4:33 PM Page 31

atmosphere and a weak remnant magneticfield, while Venus has a dense atmosphereand no magnetic field. With so manydifferent planets, the Solar System providesa vast range of laboratories for studyingthe possible interactions of exo-planetswith the winds from their host stars.

While the scales of planetarymagnetospheres are vast (up to10 million km at Jupiter), the inescapablefact is that the interaction between themagnetic fields of the planet and the Sunoccurs over a range of scales between afew km and a few planetary radii! Similarhierarchies of scales are likely to arise inother fundamental processes such asturbulence, magnetic field annihilation andparticle acceleration, leading to theastonishing diversity of structures anddynamical behaviours that characterisemost astrophysical media.

Measurements have never been made onthe smallest scales required, even in theEarth’s magnetosphere, and as a result thefundamental aspect of theelectrodynamics of the plasma Universe –the cross-scale coupling – has remainedinaccessible. To understand the genericprocesses in plasma physics, it is now vitalto move on from Cluster, which has foursatellites operating in company atrelatively large distances, to simultaneousobservations at a much larger number ofpoints. This will lead to the resolution ofboth the hierarchy of scales involved incross-scale coupling as well as the smallestand fastest plasma processes. Thepossibility of using a fleet of satellites in an

Earth magnetospheric swarm provides anexciting prospect in the timescale of CosmicVision 2015-2025.

The magnetosphere of Jupiter is anotherwonderful laboratory for studying howplasmas behave in space. With its rapidrotation, strong magnetic field and internalsources of plasma, it has been compared tobinary stellar systems and even pulsars. It isthe most accessible environment forstudying some further fundamentalprocesses such as the plasma’s interactionswith neutral gas and with the planet’smoons, magnetodisc stability, the relaxationof rotational energy and associatedenergetic processes, and the loss of angularmomentum by magneto-plasmainteractions. The last two processes areimportant in understanding accretionmechanisms that lead to the formation ofplanetary systems. A group of at least threespacecraft operating together with anoptimised plasma payload, as part of aJupiter exploration programme, willpermit the first fundamental advances inunderstanding the structure and dynamicsof this fascinating plasma environment.

Models of Europa’s structure. Far right: ice cliffs on Europa.(NASA/JPL)

LAYOUT3 11/3/05 4:33 PM Page 32

The boundary with interstellar space – theheliopause – is the final frontier of the Sun’sempire. Were a spacecraft to travel the10 billion km or more needed to reach it,and then pass through it, our instrumentswould enter the interstellar medium, acompletely distinct environment from theSolar System that has never been sampledin situ. An interstellar heliopause missionwould provide the first ‘ground truth’measurements of what the interstellarmedium really feels like, and directlyobserve the interplay between the variouscomponents of the interstellar medium– plasma, dust, magnetic fields and neutralatoms – with the Solar System’s outermostdefences.

2.2 The giant planets and theirenvironments

In addition to the Sun and theinterplanetary medium, the Solar Systemcomprises the planets, their satellites, smallbodies such as comets and asteroids, anddust. How this possibly uniqueenvironment arose and how it has evolvedare scientific questions of the highest

importance. Answering it involves thedetailed study of all of these objects. Inrespect of the major planets and theirmoons, ESA has already taken majorinitiatives with the Huygens probe to Titan,the SMART-1 mission to the Moon, MarsExpress, Venus Express and theBepiColombo mission being prepared forMercury. To continue its prominent role, ESAneeds to choose carefully further aspects ofplanetary science to pursue in the CosmicVision 2015-2025 timeframe. The main goalshould now be an in-depth exploration ofone of the giant planets in the outer SolarSystem, of which Jupiter is the mostaccessible.

When considered together with its rings, itsdiverse moons, and its complexenvironments of dust, gas and plasma, agiant planet can be seen as a miniatureanalogue of the Solar System. Studying itcan help to build a firmer understanding ofthe formation of full-scale planetarysystems. At present, in situ exploration inthe Solar System is the only way we canexamine giant planets in detail and providestrong constraints on scenarios for theirformation. In the period 2015-2025, suchinvestigations will benefit fromcomplementary studies of exo-planetarysystems. Giant planets play a key role in theevolution of planetary systems in general,and the accessible local examples aresomehow related, if only in size, to the ‘hotJupiter’ type of giant exo-planets.

3332


LAYOUT3 11/3/05 4:33 PM Page 33

The study of the giant planet systemsaddresses many important scientificquestions:

— how were the planets and their moonsformed from the solar nebula? Differentformation scenarios, such as discinstability versus core accretion, need tobe tested.

— what is the internal structure of thegiant planets themselves, and, inparticular, do they have a solid core, andof what size? These questions can beanswered by carrying out deepatmospheric soundings, throughremote sensing and in situinvestigations, coupled with accuratemeasurements of the planetarygravitational and magnetic fields.

— what are the processes involved in theformation and evolution of theatmospheres of these planets and theirmoons? As illustrated dramatically bythe exploration of the denseatmosphere of Saturn’s moon, Titan, inthe Cassini-Huygens mission, acombination of remote-sensing andatmospheric probes is needed.

— what is the internal and subsurfacestructure of their satellites, especiallythe icy ones; what is the geologicalhistory, and how does this reflect theirformation? Here, the gravitational andmagnetic fields, as well as the surfacemorphology, topology, mineralogy andcomposition, need to be studied.

— how are their complex plasma, gas anddust environments coupled to thecentral giant planet, to its satellites andrings, and to the interplanetary

medium? The in situ measurementsneed to be related to plasma injectionsfrom the solar wind, from moons suchas Io, and from the planet itself; also tothe role of planetary rotation, and theconsequences of any magnetosphericactivity such as aurorae.

The vast range of topics requiring studycalls for a staggered approach with a seriesof missions to a planet such as Jupiter.Measurements will be needed of manydifferent physical quantities: atmosphericcomposition and dynamics, gravitationaland magnetic fields, plasmas and planetaryand lunar surfaces. Possible scenarios for aJupiter exploration programme areoutlined in Chapter 5. The spin-off fromsuch investigations into understanding thestructure of giant exo-planets cannot beover-stated.

2.3 Asteroids and other small bodiesAs the primitive, leftover building blocks ofplanet formation, small bodies of the SolarSystem offer clues to the chemical mixturefrom which the planets formed. They holdunique information on the initialconditions and early history of the solarnebula, and their study is essential tounderstanding the processes by whichinterstellar material becomes newplanetary systems with the possibility ofbearing life.

ESA has already taken major initiatives inthis field, with the pioneering encountersof the Giotto spacecraft with comets Halleyand Grigg-Skjellerup, and by the dispatch

LAYOUT3 11/3/05 4:33 PM Page 34

of the Rosetta mission to cometChuryumov-Gerasimenko for a much morethorough investigation of the primordialmaterial, with an orbiter and a lander. Thenatural next step in ESA’s exploration ofsmall Solar System bodies would be asample return mission of material from oneof the near-Earth asteroids.

These objects are dynamically connected tothe family of Main Belt asteroids – they canbe considered essentially to be extensionsof it. By choosing an object belonging toone of the most primitive classes of thisfamily, and by analysing samples taken invarious well-determined geologicalcontexts, many long-standing questions canbe answered:

— what were the composition and thephysical properties of the buildingblocks of the terrestrial planets?

— what were the processes occurring inthe solar nebula accompanyingplanetary formation?

— what is the nature and origin of theorganic materials in primitive asteroids?

— are there lessons for our understandingof the origin of life in the Solar System?

— do asteroids of primitive classes containpre-solar material not yet known inmeteoritic samples?

— do they contain chondrules, the maincomponent of the carbonaceouschondrite class of meteorites, for whichthe formation process is warmlydebated?

— how do the elemental, mineralogicaland isotopic properties of the asteroidsamples vary with geological contexton the surface?

— how do space weathering and impactsaffect the surface composition of anasteroid?

— what was the timeline and duration ofmajor events, such as agglomeration,heating and degassing, and aqueousalteration?

— how did the various classes of asteroidsand meteorites form and acquire theirpresent properties, and how are theasteroidal and meteoritic classesrelated?

By far the most efficient way to addressthese questions is by a near-Earth objectsample return, making possible extensiveand unique diagnostics achievable only byground-based laboratory analyses of thesesamples. Combined with detailed imagingand spectroscopic investigations of theparent body, laboratory analysis of asteroidsamples will improve the interpretation ofall meteoritic data and provide a new

3534


Comet Tempel 1 5 minbefore and 67 sec afterDeep Impact’s strike on4 July 2005. The nucleus isabout 5 km across.(NASA/JPL-Caltech/UMD)

LAYOUT3 11/3/05 4:33 PM Page 35

understanding of all astronomical spectra ofasteroids acquired so far.

Clearly, a full understanding of thepopulations, histories and relationships ofasteroids and meteorites will eventuallyrequire sample return missions to asteroidsbelonging to each of the spectral classes. Inthe first asteroid sample return mission, theJapanese Hayabusa spacecraft will arrive in2005 at the near-Earth asteroid25143 Itokawa. Successful return of samplesin this case will unravel the nature of

differentiated S-type asteroid material. Butonly a sample return mission to one of themost primitive, carbon-rich C-type objects,as proposed here, will address the mainquestions on the origin of the Solar System.

Ultimately, exploration of the icy Kuiper beltobjects, the likely building blocks of thecores of the giant planets, will be desirable,but as they lie at the distance of Neptuneand beyond, any thorough investigation isunlikely to be feasible in the Cosmic Vision2015-2025 timeframe.

LAYOUT3 11/3/05 4:33 PM Page 36

3736


Toolkit for Theme 2

2. How does the Solar System work?

2.1 From the Sun to the edge of the Solar System

Study the plasma and magnetic field environment of theSun, the Earth, the Jovian system (as a Solar System inminiature), and out to the heliopause where the solar windmeets the interstellar medium

The Solar System, pervaded by the solar plasma and magneticfield, provides a range of laboratories to study the interactionsof planets with the solar wind

Understanding the origin of the Sun’s magnetic field requiresobservations of the field at the visible surface around the poles

In situ observation of the heliopause would provide ‘groundtruth’ measurements of the interstellar medium

2.2 Gaseous giants and their moons

Study Jupiter in situ, its atmosphere and internal structure

Study Europan surface in situ

Giant planets with their rings, diverse satellites and complexenvironments constitute systems that play a key role in theevolution of planetary systems

2.3 Asteroids and other small bodies

Obtain direct laboratory information by analysing samplesfrom a near-Earth asteroid

As building blocks in the Solar System, the most primitive smallbodies give clues to the chemical mixture and initial conditionsfrom which the planets formed in the early solar nebula

Tools

Earth magnetosphericswarm

Jupiter explorationprogramme

Solar polar orbiter

Interstellar heliopause probe

Jupiter explorationprogramme

Jupiter probes

Europa lander

Near-Earth object sample return

LAYOUT3 11/3/05 4:33 PM Page 37

The most important challenge facingfundamental physics today is to understandthe foundations of nature more deeply.Physicists know that the laws of physics asformulated at present do not apply atextremely high temperatures and energies,so that events in the first fraction of a secondafter the Big Bang are not at all understood.Matter as we know it today did not thenexist; protons and electrons formed later. Yetwhatever happened during this first instantcreated the conditions that led to everythingwe see today: atoms, stars, galaxies andpeople. Many physicists believe that in theseextreme conditions physics was governedby the ‘ultimate theory’, a single theory thatexplains and unifies all the separate lawsand forces as they appear today.

Physicists need experimental data to guidethem to this theory, to turn mathematicalspeculation into solid understanding.Experiments in giant accelerators, such asthe Large Hadron Collider (LHC) underconstruction at CERN, offer one approach.Their energies are many orders of magnitudebelow the energies in the Big Bang, butphysicists have reasons for expecting someclues to the ultimate laws to turn up inaccelerator experiments. Increasingly,however, physicists are also turning to twoother ways of finding clues to the wayphysics unifies at high energies: high-precision tests of ‘known’ laws of physics; andquantitative studies of cosmology, of thestructure and evolution of the Universe as awhole.

Cosmologists have already made threesurprising discoveries that challenge current

Chap

ter3

LAYOUT3 11/3/05 4:33 PM Page 38

physics and point toward unified theories.The first is the realisation that most of thematter in the Universe is in an unknownform, not made of the atoms and moleculesof which we are made. This is called darkmatter. The second is inflation: during thatmysterious split second after the Big Bang,the Universe seems to have expanded witha huge acceleration, ending in a smoothlyspread-out state with just enoughirregularity to have led to the formation ofgalaxies, stars and planets. No known forcecan produce this rapid expansion, butunified theories seem to provide amechanism. Even more challenging is thethird and most recent discovery: theUniverse has more recently begun toaccelerate again, albeit at a much slowerrate. The energy field producing thisacceleration is called dark energy. Itsexistence is thought to be a strong clue tothe nature of the unified theory, but theinterpretation of this clue is still unclear.

A form of dark energy was, in fact, predictedby Einstein. He called it a cosmologicalconstant, and showed that it could create arepulsive effect in the Universe, opposingthe normally attractive action of gravity. Hedid not want to make the Universe expandrapidly, but rather to explain how it couldremain static despite the inward pull ofnormal gravity. When, a few years later, theexpansion of the Universe was discoveredby Hubble, Einstein rejected hiscosmological constant.

Physicists have revived his mathematicaldevice recently to explain inflation and thecurrent acceleration, but with an important

difference: the repulsion is not constant intime. Inflation, however strong it was for atime, ended a tiny fraction of a second afterthe birth of the Universe. But physicists arenot satisfied with simply inserting amathematical term into Einstein’sequations, without a theory underlying it.They want to explain how, at least twicesince the Big Bang, some unknown darkenergy has made gravity push the Universeapart rather than try to pull it back on itself.It would be hard to overstate thechallenges that the dark energy and darkmatter present to theoretical physics, andtherefore also the opportunity for newtheories, for a new understanding offundamental physics.

Unified theories of physics do not onlypredict large-scale cosmological effects, andthey do not ‘kick in’ only at the very highestenergies. They must leave traces even inordinary physics, if we can make sufficientlysensitive measurements to see them. Manytheories predict how large these tracesshould be. Physicists in the laboratory havecreated ingenious experiments to probe thefundamental laws and look for theseviolations, but the Earth is not the bestplace to do this. Aside from the noisyenvironment, Earth-bound laboratoriescannot eliminate the effects of gravityexcept by allowing apparatus to go intofree-fall for very short times. The size andduration of many experiments is thereforeseverely limited.

Space-based astronomy has already playeda major role in identifying the majorcosmological problems facing physics, and

3938

What Are the Fundamental

Physical Laws of the Universe?

LAYOUT3 11/3/05 4:33 PM Page 39

space missions will play an even moreimportant role over the coming decades ingathering the information that physicistsrequire to solve them. There are tworeasons for this:

There are places and times elsewhere in theUniverse where matter has been forcedinto much more extreme conditions thanwe can ever hope to create on the Earth. Byprobing the very early Universe orobserving hot and dense matter verynear to black holes, astronomers canexplore the laws of physics in conditionsthat cannot be accessed in any otherway. Space-based X-ray observatories cansee hot gas on the very edge of a blackhole. Observations of the cosmicmicrowave radiation give us a directpicture of the fireball that was theUniverse 380 000 years after the BigBang. Gravitational-wave observatories inspace will study black holes in ultra-finedetail, and also have the ability to seeright through the cosmic fireball to thefirst split second after the Big Bang.

Space provides the quiet environmentnecessary for extremely delicateexperiments aimed at detecting tinydeviations from the laws of physics as wecurrently understand them. To find thetiny violations expected in our presentphysical laws, physicists need to probestringently the laws of Einstein’s generalrelativity; they must challengefundamental quantum theory – theframework that describes everydaymatter so well – with more formidableexperimental tests than have been

possible in ground-based laboratories; andthey should even probe whether spaceitself has a structure on very smalldistances, as is expected on some scale inalmost all unified theories.

In all these areas, space science has thepotential to reveal more big surprises aboutthe natural world, more unexpecteddiscoveries that will challenge our currentunderstanding of the laws of physics andguide us toward the deepest laws of theUniverse.

ESA missions such as the Hubble SpaceTelescope (ESA jointly with NASA) and theXMM-Newton X-ray observatory have alreadyprovided key insights. The LISA gravitationalwave observatory, another joint project withNASA, will be launched just before the period2015-2025, and will provide unprecedentedobservations of black holes and very possiblyof completely unexpected phenomenainvisible to conventional telescopes. CurrentNASA missions like Gravity Probe-B (GP-B)and the Wilkinson Microwave AnisotropyProbe (WMAP) are making fundamentalstudies of gravity and the early Universe, butthey are unlikely to have the sensitivity toprobe deeply enough to reveal big surprises.ESA’s upcoming Planck mission may well see,in its observations of the cosmic microwavebackground, the first evidence of thegravitational waves created in the Big Bang,which would be a major step towards theinformation needed for better fundamentalphysics.

Although these missions are alreadybreaking new ground, a more systematic

LAYOUT3 11/3/05 4:33 PM Page 40

A Bose-Einstein condensate can be created on amicrochip.

programme of missions is needed. Europeanscientists have a wealth of ideas forbreakthrough experiments and ultra-sensitive observatories in space. If theseideas can be harnessed, ESA can take worldleadership in exploring fundamental physicsin space during the period 2015-2025. Anddoing this will enable European industry tomaster unique new technologies that shouldhave much wider applications in the future.

Four areas of space science offeroutstanding opportunities for unexpecteddiscoveries in fundamental physics: tests ofphysical laws as they are understood today,observations of gravitational waves, studiesof hot X-ray-emitting matter, andinvestigations of the accelerating Universe.The first three are discussed in detail hereand the accelerating Universe is taken up inChapter 4.

3.1 Exploring the Limits ofContemporary Physics

During the period 2015-2025 it will bepossible to use several maturingtechnologies to conduct experiments inspace to look for the slight deviations in ourstandard physical laws that might containcrucial clues to the deeper unified theory ofphysics that physicists seek. The Europeanfundamental physics community respondedto the Cosmic Vision initiative with anoutpouring of suggestions for high-precisionexperiments in space aimed at the areas feltmost likely to uncover new physics.

Many of these experiments share keycharacteristics. Most require an Earth-

orbiting platform that is extremely quiet,with levels of vibration much lower than areavailable on the International Space Station.Such extreme isolation requires drag-freetechnology, such as has been demonstratedby GP-B and as will be achieved by ESA’sLISA Pathfinder mission and later by LISAitself. Many of the experiments require, inaddition, cryogenic environments –temperatures within a few degrees ofabsolute zero. This has already beenachieved in GP-B and a number ofastronomy missions. Finally, a large numberof the experiment ideas submitted by thecommunity are based on the new cold-atom technology, in which individual atomsor groups of atoms are manipulated atultra-low temperatures, where quantummechanics dominate their behaviour. Undersuch conditions, atoms exhibit a wave-likecharacter, they lose their individualidentities, and they become raw material forpotentially the most accurate measuringtools ever available. Cold-atom technologyis well-developed in ground-basedexperiments, as was recognised by theaward of the 2001 Nobel Prize in Physics forBose-Einstein condensates. Physicists arenow ready to adapt this technology tospace experimentation.

Here are some questions that the Europeanfundamental physics community would like

4140


LAYOUT3 11/3/05 4:33 PM Page 41

to answer, which together represent a broadattack on the frontiers of known physics:

Do all things fall at the same rate? Galileo showed that all things fall at thesame rate in a gravitational field, and this‘equivalence principle’ underpins Einstein’stheory of general relativity. However, unifiedtheories of physics all seem to introducetiny extra forces that allow objects made ofone kind of material to fall slightly morerapidly than objects of another. There areeven predictions of the size of theseviolations. The CNES Microscope mission willlook for these violations with a sensitivitynever achieved in ground-basedexperiments, and ESA and NASA have bothstudied proposals for an even moresensitive mission called STEP. A drag-freeexperiment in Earth orbit, using cryogeniccooling and ultra-sensitive measurementdevices to monitor the free-fall behaviour ofdifferent materials, could measure effects atthe predicted level and finally reveal theexistence of extra gravity-like forces. A cold-atom mission containing an atomicinterferometer could test the equivalenceprinciple using single atoms at a similarlevel of accuracy.

Do all clocks tick at the same rate?Einstein broadened the equivalence

principle to include clocks: all measures oftime must behave in the same way ingravitational fields. All clocks must thereforeexperience the same gravitational redshift,running slower when they are near togravitating bodies than when they are faraway. The redshift effect is well-establishednear the Earth, and is in fact built in to theoperation of satellite navigation systems(Galileo and GPS), which depend onaccurate atomic clocks for precisepositioning. But does it work the same way,to high accuracy, for other clocks, based onother physical principles? Do photon clocks(based on photons running back and forthin a cavity) or molecular clocks (based onthe vibrational frequencies of molecules) orindeed human ageing (astronauts in orbit)all go faster in orbit to the same extent? Inunified theories of physics, one wouldexpect small deviations among them. AnEarth-orbiting mission carrying severaldifferent types of ultra-precise clocks coulddetect a violation of the universality of theredshift even if it was four orders ofmagnitude smaller than our current bestlimits.

Does Newton’s law of gravity hold at verysmall distances?On the Earth and in the Solar System,Newton’s law of gravity works very well.Small corrections due to Einstein’s generalrelativity are well understood. But in someunified theories, the way that gravitydepends on the distance between objectsshould change when the separations aresmaller than a particular amount, eitherbecause of new short-range forces orbecause gravity itself changes. Because of

A Bose-Einstein condensate in the laboratory.

LAYOUT3 11/3/05 4:33 PM Page 42

the weakness of the gravitational force, wecurrently have no information fromlaboratory experiments about how itbehaves across distances smaller than afew tenths of a millimetre. Ultra-precisetests of Newton’s gravity using a drag-freesatellite in Earth orbit could improve onsimilar experiments on Earth, because ofthe quiet environment and the length oftime for which an experiment can be run.Space experiments could measure gravitydown to micron distances, an improvementby a factor of 1000 on what is knowntoday.

Does Einstein’s theory of gravity hold atvery large distances?Unified theories usually predict smallchanges in gravity in the Solar Systembeyond those that can be ascribed togeneral relativity. Although generalrelativity is very well tested today, there isstill plenty of room for surprises caused byextra fields or extra dimensions in unifiedtheories. Intriguingly, NASA cannot explainanomalies in the tracking of its Pioneer-10spacecraft, which has journeyed furtherfrom the Sun than any other. A missionusing lasers on drag-free satellites (asdeveloped for LISA) orbiting the Sun couldtest general relativity by measuring thebending of light passing the Sun. ThePioneer anomaly could be tested with aspecial package that might be part of aEuropean exploratory mission to the outerplanets, or with even better sensitivity by adedicated deep space gravity probe.A drag-free satelite in Earth orbit could testthe inverse-square-law over intermediatedistances.

Do space and time have structure?In the 19th Century, scientists regardedspace as a smooth, flat arena in whichnatural forces acted on matter. Einsteinmodified this picture by describing gravityas the curvature of space-time, although hestill believed that the old view of space wasvalid in small regions. But 20th Centuryphysics showed a more complicatedpicture. For one thing, Nature is notsymmetric under reflection in a mirror: anapproaching neutrino will always bespinning clockwise about its direction ofmotion, never anti-clockwise, no matterwhere it was produced. As anotherexample, it appears that some part offundamental physics must favour particlesover antiparticles, in order to explain theabsence of antimatter in the observedUniverse. Other losses of symmetry are alsopossible. Many physicists, including thefamous British physicist Paul Dirac, havesuggested that there might be slowchanges with time in the values offundamental constants, such as the massesof elementary particles. Alternatively, theelectric force exerted by a tiny charge, likean electron, might not be the same in alldirections. All of these effects are possiblewithin unified theories, and observations ofmore of them would give strong clues todecide which theory may be right.Experiments to test for time-dependence ofconstants or direction-dependence of the

4342


The CNES-ESA Microscope mission to test the equivalenceprinciple, to be launched in 2009. New technology willenable even more sensitive space-based tests during theCosmic Vision timeframe. (CNES)

LAYOUT3 11/3/05 4:33 PM Page 43

electric force could be performed on adrag-free spacecraft with cold-atomtechnology and/or ultra-stable clocks.

Does God play dice?In the first half of the 20th century,physicists evolved quantum theory todescribe atoms and elementary particles.They found that the theory did not predictexactly the outcome of experiments, butonly gave probabilities for variousoutcomes. They concluded that exactpredictions were impossible, even inprinciple. Einstein famously rejected thisstandard interpretation of quantum theory,using the phrase, ‘God does not play dice’.Recent ground-based experiments havemade Einstein’s point of view lookincreasingly untenable. They investigate aphenomenon called entanglement, wheretwo photons are created in such a way thatthe polarisation of one depends on that ofthe other, but neither polarisation isindividually predictable. Entangled photonsseem to behave exactly as standardquantum theory expects – withpolarisations that are random until they aremeasured – and not at all as if they had anunknown but deterministic polarisationstate that was set when they were created.And even in standard quantum mechanics,there is still an incomplete understanding of

how the probabilistic picture gives way tothe deterministic mechanics of Newtonwhen we deal with large collections ofatoms, such as footballs, weather systemsand planets. This transition is sometimesreferred to as decoherence, contrasting withthe coherent behaviour that is seen, forexample, in entangled systems.

Now, quantum theory is the foundation ofour understanding of atoms and molecules,and it is extraordinarily successful indescribing the materials of our naturalenvironment. One of the goals of unifiedtheories of physics is to extend quantumtheory to gravity, to create a theory ofquantum gravity. It is of crucial importancefor the development of unified theories,therefore, that quantum theory be testedand understood as deeply as possible. Manyexciting and deep experiments on quantumtheory are possible in space, again usingcold-atom techniques, ultra-stable clocksand drag-free spacecraft. Entanglement andcoherence/decoherence could be testedover very large and ultra-small distancescales. A space mission could create anensemble of millions of atoms in a singlecoherent ultra-cold quantum state (a Bose-Einstein condensate), and then use this as asource for an atom laser and an atominterferometer.

Can we find new fundamental particlesfrom space? All unified theories predict many moreparticles than physicists have seen so far.Most would have very high masses, beyondthe energies accessible at facilities like CERN.Dark matter may well consist of one or more

Interference fringes in an entanglement experiment.

LAYOUT3 11/3/05 4:33 PM Page 44

species of massive elementary particles.What is more, there is currently a troublingpuzzle in observations of cosmic rays, whichare high-energy particles from space. Itappears that there are more ultra-high-energy particles than one would expect,because standard cosmic rays of this energywould be slowed rapidly by scattering ofthe photons of the cosmic microwavebackground radiation. This anomaly maypoint to new kinds of cosmic-ray particlesor to new sources of conventional cosmicrays in the dark matter of the Universe.Space experiments can complement theexperiments on the ground that arecurrently looking for dark matter (so farunsuccessfully) and anomalous cosmic rays.With long observation times and the abilityto look down on large parts of the Earth’satmosphere, an orbiting cosmic-rayexperiment could accumulate data muchmore rapidly than ground-basedexperiments. In an ultra-quiet, cryogenic,drag-free environment in space, searchescan be made for special kinds of possibledark matter particles that would be difficultto detect on the ground.

Some of these questions could beaddressed using technology availabletoday, while others (particularly involvingcold atoms) require a careful programme oftechnology development to move theexperimental techniques out of thelaboratory and into space. If initiated now, afundamental physics explorerprogramme could lead to a series ofbreakthrough missions in the early part ofthe Cosmic Vision 2015-2025 timeframe.

In the longer term, these pioneering high-precision space experiments will lead tonew technologies with much widerapplicability in space: better gyroscopes,better time standards, better platforms andtechniques for observing the Earth, andbetter ways of tracking and coordinatingspacecraft. In many cases, theseimprovements will not be incremental, butwill instead be dramatic advances inperformance by several orders ofmagnitude.

3.2 The gravitational wave universeGravitational waves were predicted byEinstein almost immediately after heformulated his theory of general relativity90 years ago. They have the potential tobring us completely new information aboutthe Universe and its most extreme objects.Observable gravitational waves should beproduced by massive objects (especiallyblack holes) colliding or moving in tightorbits around one another, by the Big Bang,and possibly by unknown components ofthe dark matter of the Universe.

Visible light, radio waves, X-rays and gammarays – collectively called electromagneticradiation – have until now been theprincipal source of information forastronomers about the Universe. Butastronomers have found that only 4% of themass in the Universe is even capable ofproducing electromagnetic radiation. Therest, if it generates any signal at all, canproduce only gravitational radiation. Someof the most important places in theUniverse where we must look for clues to

4544


LAYOUT3 11/3/05 4:33 PM Page 45

fundamental physics, such as the Big Bangand black holes, will be directly visible onlythrough the gravitational waves they emit.

But gravitational waves are very weak, andthey have not yet been directly observed.The technical challenges of detecting bylaser beams the tiny motions that theycause have been conquered only recently,and a number of large-scale gravitationalwave observatories are now underconstruction on the ground. The ESA-NASALISA mission will launch in 2014 and willbe the first space mission to look at theUniverse through this new window. LISAwill observe at mHz frequencies (muchlower than those of the ground-baseddetectors), where the sources are soplentiful that the LISA team can beconfident of seeing the first of them withindays of turning the instrument on. LISA willsurvey the Universe for colliding massiveblack holes, and stringently test generalrelativity. It may even measure the darkenergy at early times.

On the other hand, LISA is unlikely to seethe cosmic gravitational radiationbackground created immediately after theBig Bang, unless the intensity of the wavesis much higher than current theoreticalpredictions indicate. In LISA’s frequencyrange, even a more sensitive missionwould not see that cosmic radiation

because it would be buried beneathgravitational waves from astrophysicalsystems, such as ordinary binary systemsthroughout the Universe. The key toobserving this radiation is to look for it atfrequencies of 0.1-1.0 Hz, between the LISAband and the frequencies observable fromthe ground. This is a cleaner band, withfewer stellar sources to mask the Big Bangradiation.

A new gravitational wave mission in theperiod 2015-2025 could open thisfrequency band. It should betechnologically more advanced than LISA,using higher-power lasers, larger mirrorsand better drag-free sensing and control.A LISA-like detector involving a single arrayof three spacecraft could by itself detectand measure the distance to every binarysource of gravitational waves in thisfrequency band in the Universe. Most willbe pairs of neutron stars or black holes ontheir way to merging. Coordinatedobservations with space-based X-ray andinfrared telescopes could use the excellentpositional accuracy of the gravitationalwave identifications to locate the systems inclusters or even in individual galaxies, andto study the subsequent merger events.Such a mission could address severalquestions in fundamental physics andastrophysics:

— it could measure the acceleration ordeceleration of the expansion of theUniverse out to high redshifts,essentially to the beginning of starformation. This would in turn answerthe question of whether the dark

A full-scale system to detect the Big Bang in gravitationalwaves. Individual configurations could be used to searchfor the earliest stars and black holes.

LAYOUT3 11/3/05 4:33 PM Page 46

energy is time-dependent or behaveslike Einstein’s cosmological constant.

— it could determine the time in thehistory of the Universe at which starformation began.

— it could sample the population ofintermediate-mass black holes bydetecting all the binary systems madeup of these objects in the observationalfrequency band, anywhere in theUniverse. These black holes are thoughtto be the highly abundant end-products of the evolution of the firstgeneration of stars. They could haveplayed a key role in the formation ofthe giant black holes in the centres ofgalaxies, and in the entire evolution ofgalaxies. Their binaries would be tracersof their population, distribution andhistory.

— it could search for and detect for thefirst time (or set stringent upper limitson the abundance of ) many plausiblebut hard-to-detect objects. Theseinclude cosmic strings (not to beconfused with the strings of stringtheory), which are very long one-dimensional mass concentrations thatarise naturally in many unified fieldtheories. Binaries of MACHOs (MassiveCompact Halo Objects), the unseenobjects near our Galaxy detected incertain gravitational lensing events,should also reveal themselves, providedthese mysterious objects are compactand relativistic.

— its superior sensitivity would allow it tosearch for other possible compact andmassive components of dark matter. Ourignorance of the dark side of the

Universe leaves open many possibilitiesfor minor or major constituents of darkmatter.

Beyond these possibilities for a single-arraythree-spacecraft mission, a more ambitioussystem involving more spacecraft andpushing the new technology to its limitsmight be capable of detecting the cosmicgravitational wave background from the BigBang, at the levels predicted by inflationtheory. These waves should have beenemitted during the first tiny fraction of asecond after the initiation of the Big Bangand should have travelled to us essentiallyunaffected by all the matter they passthrough along the way. This makes themideal probes of the laws of physics at thehighest energies. The frequency of theradiation today is related to thetemperature of the Universe when thewaves were emitted. Waves in the 1 Hzfrequency band come from a time whenthe Universe was far hotter thantemperatures at which physics isunderstood today.

The frequency band around 1 Hz is thoughtby astronomers to be an ideal ‘window’ intothis background radiation. At lowerfrequencies where LISA will operate, thestellar systems in the Universe producemore gravitational waves than we expectfrom the Big Bang, masking the cosmic

4746


A numerical simulation of two black holes about tomerge, and their emitted gravitational waves.(W. Benger/ZIB and the Albert Einstein Institute)

LAYOUT3 11/3/05 4:33 PM Page 47

background. At higher frequencies, wherethe ground-based detectors operate, theamplitude of the background radiation islikely to be much weaker.

Even at 1 Hz the cosmic background waveswill be weak, and to find them wouldrequire two detector arrays operating verynear each other. They would search for thebackground by cross-correlation – bylooking for a common component ofgravitational-wave ‘noise’ in theindependent detectors. Further spacecraftmay be needed to discriminate betweenforeground binary sources and thebackground radiation, much as the satellitesobserving the cosmic microwavebackground rely on ground-based radioobservations to identify and subtractforeground sources. The cross-correlationtechnique is already being used by ground-based detectors to search for the cosmicbackground of gravitational waves at theirhigher frequencies, but they do not havethe sensitivity to reach the predictions ofinflation theory. The advanced space-baseddetector system described here would beabout a million times more sensitive to theenergy of the background radiation thanthe upgraded Advanced LIGO detectorsthat are expected to begin operating nearthe time of the LISA launch.

Detecting the radiation coming directlyfrom the Big Bang by this gravitationalwave cosmic surveyor is the mostimportant goal that ESA’s fundamentalphysics programme could aim for.Implementation of such an ambitious dualarray would no doubt require partnerships

with other agencies. NASA is currentlydeveloping its own plans for such a mission,called the Big Bang Observer. Withplanning, the task could be done in stages,once the first array had proved thetechnology and accomplished theimportant single-array science observationsat 1 Hz. By developing the appropriatetechnologies and launching a pioneermission in this waveband towards the endof the 2015-2025 period, ESA could take adecisive step towards this goal.

3.3 Matter under extreme conditionsBlack holes are the most exotic predictionof general relativity. They have the strongestpossible gravitational fields, and yet ingeneral relativity they are among thesimplest objects to describe. The entiregravitational field of a black hole isdetermined by just three parameters: itstotal mass, its total spin angularmomentum, and its total electric charge. Itis as if extreme gravity crushes theindividuality out of these objects, so thatthey are all essentially identical, regardlessof how they were formed. Gravitationalwave detectors, especially LISA, will registergravitational waves from disturbed blackholes and from objects orbiting black holes,and they will be able to test whether realblack holes are as simple as relativitypredicts.

However, black holes also create some ofthe most extreme conditions for matter inthe Universe. Matter falling into black holesis heated to very high temperatures, makingit visible to X-ray telescopes and gamma-ray

LAYOUT3 11/3/05 4:33 PM Page 48

detectors. The giant black holes that formedvery early in the centres of galaxies seem tohave powered the quasars and to haveplayed a key role in the evolution of thegalaxies themselves.

There is even a possibility that the energythat powers quasars comes from therotational energy of spinning black holes,and that large-scale magnetic fields funnelthat energy in the form of jets of energeticparticles. Although black holes are a one-way street for matter, so that anything thatfalls into them never re-emerges, they canexchange energy and angular momentumwith their surroundings to some degree.Whilst this is understood theoretically, it hasnever been observed in detail.

Recent X-ray and gamma-ray results fromESA’s XMM-Newton, NASA’s Chandra andESA’s Integral missions have shed light onthe accretion and ejection mechanismstaking place around black holes andneutron stars, and the crucial interplaybetween black holes and galaxy evolution.Effects predicted by Einstein’s generaltheory of relativity, such as a stronggravitational redshift or the effects of rapidrotation, have just began to be detected invery bright sources. In the future, the aimwill be to probe deep inside thegravitational well of black holes andneutron stars, to provide for the first time athorough test of general relativity in thestrong field limit, to investigate the physicsof strong interactions in ultradenseenvironments, to observe the hugeamounts of gas involved in binary blackhole mergers, and to understand the violent

processes at work in hypernova explosionswhich form gamma-ray bursts and lead tothe enrichment of matter in heavyelements.

X-ray emission is typically produced wherematerial falls in a strong gravitational field.Black holes have the strongest gravity, sothe X-ray emission produced just outsidethe event horizon carries the imprint of themost extreme observable space-timecurvature. Detailed studies of the X-rayspectra and time variability give tests ofstrong-field gravity such as the existence ofa last stable orbit, the closest possiblelocation of matter around the black hole.

4948

A jet from an accreting black hole (illustration byA. Hobart).

LAYOUT3 11/3/05 4:33 PM Page 49

The mass and the angular momentum ofthe black hole can be measured by time-resolved X-ray spectroscopy, using theaccreting material as a ‘test particle’ for thespace-time structure very close to the blackholes. Other effects predicted by Einstein’stheory of gravity, like strong bending of thelight, epicyclic motions and precessionaround the spin of the black hole, can betested directly. The ‘cosmic censorship’conjecture, according to which the spin ofblack holes is limited by their mass, can alsobe tested by studying a sufficiently largenumber of them.

Neutron stars are only slightly less extremethan black holes in terms of gravity, butwith the crucial difference that they have asurface rather than an event horizon, sotheir internal structure has observableconsequences. This is important, as thestructure of matter is not well understoodat the super-nuclear densities expected inthe core of a neutron star. X-rayobservations give diagnostics of thestrength of gravity close to, or even on thesurface of, the neutron star, and hence givean observational constraint on the centraldensity, constraining models of the strong

interaction between nuclear particles.Orbital motions of the accreting materialaround neutron stars and effects of stronggravity on the matter being episodicallyejected from the surface can be used toconstrain directly the physical state of theultra-dense material inside the neutronstar, possibly creating exceptional states ofmatter, such as massive particles, super-fluid baryons or quark-gluon plasma.Similarly, X-ray spectroscopy with XMM-Newton has yielded the first measurementof the surface magnetic fields in anisolated neutron star, opening new ways toprobe its extraordinary nuclear physics.

A large-aperture X-ray observatory,which could probe gas very close to blackholes and examine neutron stars in greatdetail, is considered in its broaderastrophysical context in the next chapter(Sections 4.2 and 4.3). The obvious synergybetween the gravitational wave and X-rayviews of black holes excitingly suggeststhat an observational understanding ofstrong gravity is within reach during theCosmic Vision timeframe. A gamma-rayimaging observatory is also mootedthere.

LAYOUT3 11/3/05 4:33 PM Page 50

5150


Toolkit for Theme 3

3. What are the fundamental physical laws of the Universe?

3.1 Explore the limits of contemporary physics

Probe the limits of general relativity, symmetry violations,fundamental constants, short-range forces, quantumphysics of Bose-Einstein condensates, and ultra-high-energycosmic rays, to look for clues to unified theories

Use the stable and gravity-free environment of space toimplement high-precision experiments to search for tinydeviations from the standard model of fundamental interactions

Test the validity of Newtonian gravity using a trans-Saturn drag-free mission

Observe from orbit the patterns of light emitted from the Earth’satmosphere by the showers of particles produced by theimpacts of sub-atomic particles of ultra-high-energy

3.2 The gravitational wave Universe

Make a key step towards detecting and studying thegravitational radiation background generated at the BigBang. Probe the Universe at high redshift and explore thedark Universe

Primordial gravitational waves, unaffected by ionised matter, areideal probes of the laws of physics at the fantastic energies andtemperatures of the Big Bang. They open an ideal window toprobe the very early Universe and dark energy at very earlytimes

3.3 Matter under extreme conditions

Probe general relativity in the environment of black holesand other compact objects, and investigate the state ofmatter inside neutron stars

The study of the spectrum and time variability of radiation frommatter near black holes shows the imprint of the curvature ofspace-time as predicted by general relativity. This has strongimplications for astrophysics and cosmology in general

Tools

Fundamental physicsexplorer programme

Deep space gravity probe

Space detector for ultra-high-energy cosmic rays

Gravitational wave cosmic surveyor

Large-aperture X-ray observatory

LAYOUT3 11/3/05 4:33 PM Page 51

Since antiquity, the Earth’s inhabitants haveobserved the sky with curiosity andperspicacity, taking advantage oftechnological progress to help understandwhat the Universe is made of. Our presentknowledge is the result of centuries ofcontinuous cross-fertilisation betweenastronomical observations and theoreticalconstructions. Successive steps have takenmankind closer and closer tocomprehending the complexity, origin andevolution of the Universe: by recognisingthat we live in a planetary system and thatthe Earth is orbiting the Sun; by establishingthat the Sun is embedded in a spiral galaxy,far from its centre; by demonstrating thatthe Universe is expanding and laterdiscovering that this expansion isaccelerating; and realising from dynamicevidence that most of the matter in theUniverse is in an unknown form, called darkmatter.

Previous chapters have anticipated severalaspects of the continuing quest. Themystery of how star and planetary systemsform, the detection and characterisation ofexo-planets and their atmospheres, and theconditions for the emergence of life arethemes in Chapter 1. The origin of the SolarSystem features in Chapter 2, together withthe need to understand the Sun’sbehaviour. Chapter 3 shows how muchphysicists now rely on the observation ofastronomical objects and events tounderstand the fundamental physical lawsof nature.

Beyond these fascinating subjects, recentdiscoveries have transformed our wider

Chap

ter4

LAYOUT3 11/3/05 4:33 PM Page 52

view of the Universe. Here is a smallselection of them:

— the observational confirmation of anearly phase of accelerated expansion,called inflation, which took place duringthe first fractions of a second of the lifeof the Universe, and which wastheoretically predicted in the 1980s.

— the recent, totally unexpected discoveryof a later and continuing phase ofaccelerated expansion of the Universe,which leaves us looking for the drivingforce behind it. Termed dark energy, thiscomponent of the Universe currentlyhas no clear explanation in terms of acomprehensive physical model, andremains a big challenge forfundamental physics (see alsoChapter 3).

— the observation of galaxies at ever-increasing distances, notably with theHubble Space Telescope and XMM-Newton in space and large telescopesfrom the ground, such as the Very LargeTelescope (VLT) at the ESO or the Kecktelescopes in Hawaii.

— a much more precise estimation of theage of the oldest stars in the Galaxy,and therefore of a minimum age of theUniverse, using data from ESA’sHipparcos mission – results nowconfirmed independently by NASA’sWilkinson Microwave Anisotropy Probe(WMAP) observations of the cosmicmicrowave background.

— the discovery of the origin of theextremely violent explosions known asgamma-ray bursts, thanks initially to theItalian-Dutch satellite BeppoSAX.

— the discovery of strong gravity effectsaround black holes, including thosefrom rapid rotation, observed in X-rays,as well as many new physicalcharacteristics of neutron stars,including magnetic field measurementswith XMM-Newton and Chandra.

These discoveries are the results of bothground-based and spaceborneobservations. The contribution from spacehas been, and will continue to be, essentialfor two major reasons. Being free of theabsorption caused by the Earth’satmosphere, they open up the whole rangeof electromagnetic radiation emitted in theUniverse. Secondly, space provides anextremely stable environment for theoperation of instruments, so facilitatinguniquely sensitive and accuratemeasurements.

As a consequence of a fantastic increase inour knowledge of the Universe in the pasttwo decades, fundamental questions cannow at least be better identified andformulated. Here are some examplesdirectly related to this chapter, mainlydealing with the origin and evolution of theUniverse and the formation and evolutionof the structures that we see now:

— how did the Universe originate andwhat happened in the very early phasesof its existence? What can be observednow, to learn about the extremephysical conditions at that early epoch?

— less than 5% of the mass of theUniverse has been identified asordinary matter. What is the nature of

5352

How Did the Universe Originate

and What is it Made of?

LAYOUT3 11/3/05 4:33 PM Page 53

dark matter, which represents about23% of the mass?

— what is the origin and future of theaccelerated cosmic expansion? What isthe nature of dark energy which seemsto be responsible for it – and whichcontributes most of the content of theUniverse?

— how were the first luminous objects inthe Universe ignited? When and howdid the very first stars form, evolve andexplode? What history of stars andsupernovae gave rise to the chemicalelements we take for granted?

— how, when and why does a black holeform? How does it grow? What happenswhen two black holes merge?

— what is the history of the supermassiveblack holes that we now observe? Andhow do they interact with their hostgalaxies?

The most important scientific goals that ESAcould set itself, on behalf of Europe, nowinclude: detecting imprints of the very earlystages of the evolution of the Universe inradiation observable today; unravelling thenature of dark energy and dark matter;understanding how the observableUniverse took shape, and how it evolves

through the violent mechanisms takingplace in interaction with black holes andneutron stars. These scientific issues willremain at the centre of cosmological andastrophysical interest for at least the nexttwo decades.

4.1 The early UniverseAstronomers have found strong evidencethat the Universe underwent a period ofvery strongly accelerated expansion a split-second after the Big Bang. This is calledinflation. But probably the biggest surpriseto astronomers in the past decade has beenthe discovery that the current Universe hasentered another period of acceleration,albeit at a much slower pace. Thegravitational effect that would normallyattract galaxies to each other is beingoverwhelmed by an apparent repulsiondriving galaxies apart faster and faster.Einstein anticipated this possibility with hiscosmological constant, which represents anenergy density called dark energy and anassociated negative pressure that, in effect,converts gravity into anti-gravity, creatingthe necessary repulsion. But Einstein’sconstant was an ad hoc addition to hisequations for which he had no physicalexplanation (see Chapter 3). It is crucial tomeasure the amount and time-dependenceof today’s dark energy in order to obtainclues to what is producing it. This will be asimportant and urgent a problem in theperiod 2015-2025 as it is today.

Dark energy is estimated to represent about70% of the total mass-energy budget in theUniverse, and there are two powerful

Two of the most important scientific goals that ESA couldset, on behalf of Europe, are detecting the imprints of thevery early stages of the evolution of the Universe inradiation observable today, and understanding how theUniverse, as we observe it today, took shape.(NASA/WMAP Science Team)

LAYOUT3 11/3/05 4:33 PM Page 54

methods for finding and investigating it.One is to study weak lensing, the slightbending of light caused by the gravitationalfield produced by the large-scaledistribution of matter in the Universe. Theother is to make precise measurements ofthe brightness and redshift of largenumbers of exploding stars, supernovae ofType Ia, at very large distances, in order totest the cosmic geometry and rate ofexpansion. Both kinds of measurementsrequire a space-based telescope with a verywide field of view and the ability to makeimages in visible and near-infrared light.Europe's leading role in wide-field imagingis a major asset in this domain.Observations by such a wide-field optical-infrared imager would complement theinvestigations of gravitational wavesdiscussed in Chapter 3.

Theoretical models predict that the inflationat the origin of the Universe, when it isbelieved to have undergone a phase ofextremely rapid expansion, should beobservable in the shape of the initialdensity fluctuations from which the firststars and galaxies originated. Thesepredictions have been impressivelyconfirmed by recent observations, notablyby NASA’s WMAP. More subtle information

about inflation will come from thedetection of temperature fluctuations in thecosmic microwave background radiationthat were caused by primordial large-scalegravitational waves created in the Big Bang.The physical mechanism driving inflation isunclear, and competing theories makedifferent predictions about the amplitudeand the shape of the primordialgravitational wave spectrum. Observingsuch a wave spectrum will provide the keyto deciphering the very beginning of thecosmos.

The first possibility is to characterise theprimordial gravitational waves indirectlyfrom their imprint on the polarisationproperties of the cosmic microwavebackground. The weakness of the signalmakes space-based observationsmandatory. An all-sky mapper forpolarisation of the cosmic microwavebackground would capitalise on European

5554


The Universe 380 000 years old. This image, obtained withWMAP at microwave wavelengths, reveals 13 billion

year-old temperature fluctuations (shown ascolour differences) that correspond to the

seeds that grew to become thegalaxies. (NASA/WMAP Science

Team)

The content of the Universe. Lessthan 5% of the mass of theUniverse has been identified asordinary matter. 23% is unseendark matter, detectable only by itsgravitational effects. The remaining 73%is the mysterious ‘dark energy’, which seemsto be responsible for the accelerated cosmicexpansion observed today. (NASA/WMAP Science Team)

LAYOUT3 11/3/05 4:33 PM Page 55

expertise in observing the background.Indeed, ESA’s Planck mission (2007) is a firststep in this study, as it will produce a multi-frequency all-sky map of the cosmicmicrowave background, albeit with only alimited sensitivity to polarisation. The follow-up project should generate a multi-frequency all-sky map of much greatersensitivity than Planck, so as to characterisecompletely the polarisation parameters ofthe cosmic microwave background radiation.

Another approach to the circumstances ofinflation relies on the direct detection of theprimordial gravitational wave background,the emission of which marked the end of theinflation era, and which might even containinformation about the Universe beforeinflation set in. This approach, calling for agravitational wave cosmic surveyor, wasdescribed in Chapter 3.

Matter spirals into a blackhole. Relativistic jets spoutfrom the vicinity of thecompact object. X-rayemission is produced assurrounding gas isaccreted by the black hole.This high-energy radiationis not just a witness to theexistence of black holesbut also reveals the rate atwhich they grow to theirhuge masses.

4.2 The Universe taking shapeTracing cosmic history back to the timewhen the first luminous sources ignited, thusending the dark ages of the Universe, hasjust begun. At that epoch the intergalacticmedium was reionised, while large-scalestructures increased in complexity, leadingto galaxies and their supermassive blackholes. The merging of galaxies, their star-formation history, their relationship toquasars and their interactions with theintergalactic medium are all processes thatwe have started to analyse with NASA-ESA’sHubble Space Telescope, ESA’s XMM-Newtonand NASA’s Chandra, and other telescopesobserving at complementary wavelengths,back to a time when the Universe was onlyabout 10% of its current age.

Pushing this history back to still-earlier timeswill be one of the great achievements of

LAYOUT3 11/3/05 4:33 PM Page 56

Hubble’s successor, the NASA-ESA-CSAJames Webb Space Telescope (JWST). Therapid evolution of this research arearequires the flexibility provided byobservatory-type missions, including ESA’sHerschel, and by the ALMA ground-basedobservatory. But even taking into accountthe gains of the next 10 years, severalquestions will be left unanswered. Inparticular, JWST will miss the first clusters ofgalaxies and the precursors of quasars,expected to have central black holes with amuch lower mass and luminosity thanthose seen closer in the cosmos. These willbe best observed in X-ray.

As observational cosmology necessitates amulti-wavelength approach, no singleobservatory can complete the cosmicpicture. However, a large-aperture X-rayobservatory will be an early priority. It will

be able to trace clusters of galaxies back totheir formation epoch, making possible thestudy of the early heating and chemicalenrichment of the intracluster gas, theirrelation to black hole activity, and theassembly of the clusters’ galaxy population.Such an observatory should also be able todetect and characterise the precursors ofquasars and locate the mergers ofsupermassive black holes expected to bedetected by LISA. These objectives willrequire high sensitivity, with a collectingarea above 10 m2, and a wide field of viewcovering at least 5 arcmin for viewingextended objects. A field of 15 arcminwould substantially increase theserendipitous science return and the surveypotential for locating the most extremeobjects in the high-redshift Universe. Highspatial resolution (< 5 arcsec) will beneeded to avoid source confusion. A soft

5756


LAYOUT3 11/3/05 4:33 PM Page 57

X-ray spectroscopy capability should makepossible the detection of the missing half ofthe baryons in the local Universe, mostlikely hidden in the warm-hot intergalacticmedium.

Although JWST will register the redshiftedvisible light from very distant objects(redshifts up to z~10) it will miss the star-forming regions hidden by dust. They willbe observable, in the longer term, only by anew-generation far-infrared observatory.This instrument will be essential to resolvethe far-infrared background glow intodiscrete sources and so locate as much as50% of the star-formation activity, which iscurrently concealed from our view by dustabsorption. The far-infrared observatory willalso resolve star-formation regions in nearbygalaxies, both isolated and interacting, andidentify through spectroscopy the cooling ofmolecular clouds with primordial chemicalcomposition. These goals call for a resolutionof about 1.5 arcsec at wavelengths around200 µm.

Other interesting information, especially onthe warm-hot intergalactic medium andsupernovae of Type Ia at low redshifts,would be obtainable using high-resolutionultraviolet spectroscopy.

4.3 The evolving violent UniverseNature offers astrophysicists the possibilityof observing objects under much moreextreme conditions, in terms of gravity,density and temperature, than anythingfeasible on Earth. On the one hand, blackholes and neutron stars are unique

laboratories where the laws of physics canbe probed under these extreme conditions(Section 3.3). On the other hand, the sameobjects were the driving engines of thebirth and evolution of galaxies, of thecreation of heavy elements such as iron,and more generally, of the transformationof the primordial hydrogen and heliumfrom which stars and galaxies were firstbeing formed.

Recent results show that supermassiveblack holes exist in the cores of mostgalaxies and that there must be a direct linkbetween the formation and evolution of theblack holes and of their host galaxies. X-rayemission is produced as surrounding gas isaccreted by the black hole. This high-energyradiation is not just a witness to theexistence of the black holes but also probesthe rate at which these black holes grow totheir current huge masses. Systematic, high-sensitivity X-ray observations of thesegrowing supermassive black holes alongcosmic history will give unprecedentedinformation on the growth of large-scalestructures in the Universe and on theformation of galaxies. It is also of the utmostimportance to understand the feedbackbetween this process and the formation ofstars and the galaxies themselves, for whichthe X-ray observations will need to becomplemented by far-infrared observationsof the same objects to map star formationactivity (see Section 4.2).

Thanks to another breakthrough of the past10 years, the extremely bright and briefemissions of gamma-ray bursts are nowthought to be produced by a rapid

LAYOUT3 11/3/05 4:33 PM Page 58

accretion of gas onto new black holes,resulting from the merging of neutron starsor the dramatic explosion of a high-masssupernova or hypernova. Capture of debrisfrom the explosion results in an extremerate of mass accretion, which can power anultra-relativistic jet of matter. This processcan be used to probe the formation rate ofhigh-mass stars that give rise to thehypernovae, out to very high redshifts andthe epoch of galaxy formation.

Debris escaping from the scene dispersesthe heavy elements formed bynucleosynthesis in the massive stars, intothe interstellar and intergalactic medium.We can witness this process in full detailwhen it happens very close to us, in theremnants of supernovae in our own Galaxy.The transported energy also heats the gasand suppresses star formation. The chemicalabundances in the gas on these large scalescan be determined from X-ray lineemission, and reflect the supernova rateintegrated over time, while nuclear lines atgamma-ray energies from radioactiveisotopes give a snapshot of recent activity.Comparison of the abundances in the localand high-redshift Universe will show theevolution of chemical enrichment and theimpact of supernova feedback of energy onthe growth of large-scale structures in theUniverse. Comparison of the abundances ofelements in the gas of galaxies, clusters ofgalaxies and in the intergalactic mediumwill shed light on the life-cycle of matter inthe Universe.

When two supermassive black holes mergein a galaxy, they produce X-rays and

gravitational waves. Simultaneousobservations of these events by the X-rayobservatory and by the gravitational wavedetector LISA, described in Section 3.2,would bring complementary information.By pinpointing the galaxy, the X-raydetection will resolve any uncertainties indirection in the gravitational wavesignature, and establish the distance of theevent unambiguously.

Most of the topics quoted above build onsuccesses achieved with ESA's XMM-Newton. They are also being addressed bythe US (RXTE and Chandra) and Japanese(ASCA and Astro-E2) space observatories.For Europe to maintain its lead inunderstanding the physics of the violentUniverse, the next major step requires alarge-aperture X-ray observatory of highsensitivity (~10 m2 collecting area) over abroad bandpass, ideally 0.1-50 keV, in orderto handle the large photon rates of a varietyof events. High spatial resolution

5958


Observed by XMM-Newton, the Lockman Hole providesthe deepest ever X-ray survey of this region whereobservation of the early Universe is facilitated by therelative absence of intervening, absorbing material. Morethan 60 new X-ray sources were detected in the 5-10 keVband alone. (G. Hasinger, Max-Planck-Institut fürextraterrestrische Physik (MPE), Garching, D).

LAYOUT3 11/3/05 4:33 PM Page 59

(~1-2 arcsec) will be needed to avoidsource confusion, and time resolutiondown to a few microseconds to probe therelevant timescales. These performanceswould, for example, probe theabundances of clusters and groups ofgalaxies out to redshifts of 1-2, and trackchanges in the accretion flows onto blackholes. The specifications are compatiblewith those for a large-aperture X-rayobservatory applied to studies of theUniverse taking shape (Section 4.2) and ofmatter under extreme conditions(Section 3.3).

Closer to us, the supernova history of ourown Galaxy will soon be much clearerthrough the spectroscopic diagnostics ofMeV lines detected by ESA’s Integralmission. By the end of the 2015-2025period, or soon after, the next-generationdetectors at these high energies (bandpass100-2000 keV) will have a sensitivity twoorders of magnitude better than Integral’s.They would enable a gamma-ray imagingobservatory to complete the supernovahistory of the Milky Way – and then to dothe same for all the galaxies in the LocalGroup.

LAYOUT3 11/3/05 4:33 PM Page 60

6160


Toolkit for Theme 4

4. How did the Universe originate and what is it made of?

4.1 The early Universe

Investigate the nature and origin of the Dark Energy that isaccelerating the expansion of the Universe Gravitational lensing by cosmic large-scale structures, and theluminosity-redshift relation of distant supernovae are the clues

Investigate the physical processes that led to a phase ofdrastic expansion in the early UniverseGravitational waves from the Big Bang should leave imprints ofinflation in polarisation of the cosmic microwave background

Directly detect gravitational waves from the first momentsof the Big BangThis means operating in a new frequency window (0.1-1.0 Hz)

4.2 The Universe taking shape

Find the very first gravitationally-bound structures thatwere assembled in the Universe – precursors to today’sgalaxies, groups and clusters of galaxies – and trace thesubsequent co-evolution of galaxies and super-massiveblack holes

Resolve the far-infrared background into discrete sources,and the star-formation activity hidden by dust absorption

4.3 The evolving violent Universe

Trace the formation and evolution of the super-massiveblack holes at galactic centres – in relation to galaxy andstar formation – and trace the life cycles of chemicalelements through cosmic history

Examine the accretion process of matter falling into blackholes by the spectral and time variability of X-rays andgamma-rays, and look for clues to the processes at work ingamma-ray bursts

Understand in detail the history of supernovae in ourGalaxy and in the Local Group of galaxies

Tools

Wide-field optical-infraredimager

All-sky mapper forpolarisation of cosmic

microwave background

Gravitational wave cosmic surveyor


Far-infrared observatory


Gamma-ray imagingobservatory

LAYOUT3 11/3/05 4:33 PM Page 61

The fundamental science questionsaddressed in Chapters 1 to 4 need to beanswered through specific experiments oncarefully selected space missions.Considerable effort will be required tomove forward from embryonic concepts forprojects to mission profiles that aretechnically, fiscally and programmaticallyfeasible. For any suite of potential missions,such as those foreseen in Cosmic Vision2015-2025, the timely and systematicdevelopment of new technologies will becrucial for its success.

While the details of the technologiesrequired will mature as the missioncharacteristics become clearer, it is stillpossible to identify at an early stage manyof the key developments. Technologies thatmay be common to a number of possiblefuture missions can also be established. Forexample, deployable mirror systems withlarge apertures are a common requirementfor various astronomical missions, althoughthe design details differ significantly,depending on wavelength. A commonreadout technology providing randomaccess for large sensor arrays, at differentwavelengths, also merits considerableeffort.

For each of the scientific Themes 1 to 4, andtheir sub-themes, we identify in whatfollows the investigative approach and thepossible technologies that should bedeveloped to address them mosteffectively. The ‘tools’ selected by scientificcriteria become the basis for identifyingembryonic concepts for missions, andestablishing a provisional sequence based

Chap

ter5

LAYOUT3 11/3/05 4:33 PM Page 62

purely on their levels of technologyreadiness. Missions currently within the ESAprogramme need to be considered too,since they will also provide importantlearning curves in the mission, technologyand science areas. For example, thedevelopment of a gravitational wave cosmicsurveyor, to look for signals from the BigBang, will clearly need to await theimplementation of the ESA-NASA LISAmission. In other cases, such as planetarymissions, fixed launch windows governedby celestial mechanics will affectprogramme planning.

5.1 Theme 1: the conditions for planetformation and the emergence of life

The tools identified in Chapter 1, andsummarised in Table 1.1, span a wide rangeof requirements, from large telescope arraysto miniaturised landers. Here, we discussthem from a technological point of viewunder the various subheadings into whichthe main question was divided.

5.1.1 From gas and dust to stars andplanets

In order to develop this field further and tobuild on ground-based capabilities, a far-infrared observatory with high spatial andlow to high spectral resolution will berequired, in the range 25-300 µm. The studyof dust and gas in stellar discs and proto-stars in the process of formation willdemand an instrument with a spatialresolution of ~10 milliarcsec and tworanges of spectral resolution: a low onearound 1000 and a high one of about 105.Such an instrument will be based on

interferometric principles, similar to thosealso required at near-infrared wavelengths(Section 5.1.2). The configuration of themulti-spacecraft constellation making upsuch an interferometer will require detailedstudy. Although many of the keytechnologies could be common to othermissions, some specific additionaltechnologies, involving low- and high-resolution spectrometers, will need to bedeveloped. Table 5.1.1.1 summarises the keytechnologies required for such aninterferometer. Particular effort will berequired in the development of the far-infrared sensors.

5.1.2 From exo-planets to biomarkersThe detection of new planetary systemsnaturally leads to a desire to search forexo-planets in the habitable zone, followedby characterisation of those planets todetect the spectral tracers of a planet’satmosphere, e.g. water, ozone and carbondioxide and possibly also methane, whichmay include signs of life. This will require ahigh ratio of stellar light rejection (105-106)added to a high sensitivity for detecting the

6362

Technology Requirements

Technology Comment

Membrane reflectors Low-mass system

Adaptive optics Figure control

Interferometer components

Constellation control Metrology, micro-propulsion and control

Thermal shields and cryocooler Long-life coolers

Far-infrared sensor (bolometer/ High-sensitivity arrays semiconductor, photo-con)

Table 5.1.1.1: Technologies required for a far-infrared interferometer.

LAYOUT3 11/3/05 4:33 PM Page 63

light emitted by exo-Earths. Theseobjectives would be addressed by a near-infrared nulling interferometer with highspatial resolution (images with 10-100times more detail than will be possibleeven with instruments such as the JWST)and low-resolution spectroscopy (R ~ 20-50).

Such an instrument will require thedevelopment of a four-spacecraftconstellation with a variable baseline. Thechallenges with such an opticalconfiguration are significant, particularly forcombining the optical beams. Fig. 5.1.2.1shows one possible mission profile. Threetelescopes on three free-flying spacecraftoperate together with a separate centralbeam-combiner spacecraft. The separationbetween these spacecraft will varydepending on the target star and itsassociated habitable zone. Such a missionwould be capable of observing planetarysystems around all stable K, G and F starsout to a distance of 25-30 pc (~80-100 lightyears) resulting in ~300-500 candidateplanetary systems. Further spectroscopicobservations with the interferometric

constellation will characterise the planetaryatmospheres. The key technologies specificto such a mission are identified inTable 5.1.2.1 (for brevity, some of thegeneric technologies needed to achieveformation-flying are not listed).

Looking beyond this key step, with thenulling interferometer, the technologicalprospects for the terrestrial planetastrometric surveyor proposed inSection 1.2 can be judged in relation toNASA’s Space Interferometer Mission-PlanetQuest. This US project, expected in 2011,intends to use interferometry with visiblelight, on a 10 m baseline, to measure starangular motions to 1 µarcsec, and so detectthe stellar wobbles among the nearest starsdue to orbiting planets down to Earth-sizedobjects. A European mission a decade later,building on Gaia’s expertise in globalastrometry, could reasonably aim at thenanoarcsec accuracy, and achieve acomplete census of terrestrial planetswithin 100 pc of the Sun.

On the other hand, the goal of eventuallyimaging terrestrial planets orbiting otherstars, mentioned in Section 1.2, wouldrequire a large optical interferometer thatmay be beyond reach in the Cosmic Vision2015-2025 timeframe.

Technology Comment

Single-mode waveguide Fibre optics or integrated optics

Nulling interferometer components Optical delay line, phase shifter, etc

Constellation control Metrology, micro-propulsion and control

Near-infrared sensors and sensor/ High-sensitivity arrays + cryocoolersoptics coolers

Table 5.1.2.1: Technologies required for a near-infrared nulling interferometer.

Figure 5.1.2.1: The near-IR nulling interferometer using a4-spacecraft constellation at L2. The three beamscollected by the telescope spacecraft are brought togetheron the central beam-combiner. A constellation of fourappears to be the minimum required to establish theatmospheric characteristics of terrestrial planets (inset)within the habitable zones of stars within 25 pc.

LAYOUT3 11/3/05 4:33 PM Page 64

5.1.3 Life and habitability in the SolarSystem

For the theme of life and habitability in theSolar System, Mars is clearly a major targetwithin Cosmic Vision 2015-2025. Naturally,the programme must take account of themajor activities envisaged within ESA’sAurora Programme and NASA’s planning.Mars landers with science packagesincluding biochemical and geophysicalinstrumentation are an important earlygoal. Key requirements are driving the initialstudies:

— to land on rough and high terrain, achallenge for the entry, descent andlanding system (EDSL; Fig. 5.1.3.1);

— to penetrate to depths of severalmetres, for subsurface science;

— to provide mobility for scienceinstruments (Fig. 5.1.3.2).

The technologies and surface sciencepackages needed to meet these require-ments are listed in Tables 5.1.3.1 and 5.1.3.2.

The long-term goal is, of course, a Marssample return. The aim would be to gathersoil samples and deliver them to the Earth,from a specified set of locations previously

studied in situ by landers or their associatedrovers. This further step is a major challengethat needs careful technology preparation.Section 5.2.3 describes a sample returnfrom a low-gravity environment, in this casea near-Earth asteroid.

The Jovian system, often compared to aminiature Solar System, is also a major

6564


Figure 5.1.3.1: A possible design of a 50 kg lander forMars with a payload mass of ~12 kg. The completesystem including the EDLS would require about 150 kg fora secure landing. Two landers of this class could beaccommodated on an orbiter like Mars Express, andinserted into a controlled manner from a highly ellipticalMars orbit. (ESTEC Concurrent Design FacilityDemoLander study performed for the ExplorationProgramme/General Studies Programme.)

Technology Comment

Spin-up & eject mechanism Improved accuracy

Parachutes Optimisation and extensive tests

Thrusters Velocity control during descent

Guidance, navigation & control Descent control by radar/lidar + camera

Airbags Sizing/pressure optimisation and test

Front heatshield Increased size and testing

Back cover Release system and test

Table 5.1.3.1: Technologies for the Entry, Descent and Landing System (EDLS) required for aninitial secure landing on Mars.

Technology Comment

Deep subsurface (5 m) mole Qualification of existing system

Compact subsurface biochemistry Mole packaging and testsystem

Compact subsurface geophysics Mole packaging and testsystem

Mini-rover Test and qualification

Rover geochemistry package Development and qualification

Table 5.1.3.2: Technologies for the surface science packages required to exploit an initial securelanding on Mars.

Figure 5.1.3.2: The release of one of two landers from aMars orbiter before the initiation of the EDLS (left). On thesurface, the lander would also require a mobile element(right). Here, a European mini-rover with a range of 50 mand carrying a geochemistry payload of 1 kg is shown.

LAYOUT3 11/3/05 4:33 PM Page 65

target within Cosmic Vision 2015-2025. Itneeds to be studied and explored in acoherent and systematic manner through aJupiter exploration programme (JEP).Those parts of JEP that focus on Jupiter’smagnetosphere and interior figure inSections 5.2.1 and 5.2.2. In the context ofthe present theme, Jupiter’s icy moonEuropa is one of the few places where liquidwater may be found in the Solar System,making it a prime candidate for the searchfor life beyond the Earth. Remote sensingfrom a Europa orbiter is certainly anoption. The deployment of microprobeEuropa landers can also be considered,provided that they are technically feasibleand the likely science return justifies theeffort and resources.

A possible scenario foresees two smallspacecraft (400 kg and 600 kg), one actingas a relay spacecraft (JRS1) in a highlyelliptical orbit around Jupiter, outside thehigh radiation zones, while the other (JEO)enters a polar orbit around Europa. There,the orbiter has a maximum lifetime ofaround 2 months, after which theperturbation by Jupiter’s gravity will set theorbiter on an unavoidable collision coursewith the icy moon. The expected electronradiation is up to 2 Mrads during those2 months, assuming shielding by 4 mm ofaluminium, so this highly hostileenvironment will require innovativeapproaches in the spacecraft design.

Global mapping and analysis of the moon’ssurface can be obtained in 30 days by JEO,with a stereo micro-camera, UV-camera,visible/near-infrared mapping spectrometer,

and a laser altimeter, together with aminiaturised subsurface radar and a low-resource gamma-ray spectrometer.A magnetometer, radiation monitor,radiometer and a low-resource microprobecould complete the core payload of JEOand stay within the available spacecraftresources.

As for Europa landers, a single penetratingmicroprobe (1 kg) might be considered foran early mission, to perform a local in situanalysis of Europa’s subsurface. It can bereleased either shortly before Europa orbitinsertion or shortly after. Since there is nosignificant atmosphere around Europa, themicroprobe must survive the shock of ahigh-speed impact on the icy crust.Currently, this is considered to beunfeasible, although studies continue.

Figure 5.1.3.3: An array of four microprobes for Europawith a controlled descent system (top right) together withthe distribution of key sensors and subsystems (top left).Adoption of this type of system to perform a controlledlanding on the surface of the Jovian moon (below; 2005by Don Dixon/cosmographica.com) would require at least20 kg mass allocation, so taking a major fraction of theresource budget of the payload suite (30 kg) of the Europaorbiter JEO. This should therefore be considered as a lateroption in the Jupiter exploration programme.

LAYOUT3 11/3/05 4:33 PM Page 66

For a later phase in the Jupiter explorationprogramme, landers making controlleddescents from a second Europa orbiter canbe contemplated.

In Fig. 5.1.3.3 an illustrative 20 kg microprobepayload consists of a thermometer,spectrometer and seismic and acousticsensors. The tracking and communicationbetween this very low-power probe and theorbiter will be a significant challenge byitself. Another major challenge will be theattitude control of the probe, since Europadoes not have any significant atmosphere tostabilise it.

5.2 Theme 2: how does the Solar Systemwork?

Among the most far-ranging tools forCosmic Vision 2015-2025 are those that willcontinue ESA’s exploration of the Sun’sempire, but now with the additionalobjective of making better sense of theenvironments and planets of other stars, andtheir potential habitability. New technologiesto be shared between different kinds ofprojects will greatly extend the possibilitiesof exploration at reasonable costs.

5.2.1 From the Sun to the edge of the SolarSystem

Investigations of plasma physics, and what itcan teach us about the complex behaviourof magnetic fields and charged particlesthroughout the Universe by closer study ofthose in the Solar System, remain a majorgoal for ESA in Cosmic Vision 2015-2025. Anew opportunity arises in the use of largeswarms or small groups of identical micro-

satellites for cooperative observations ofplasma behaviour in various settings. Inparticular, Chapter 2 specified theexploration of two very differentenvironments, in the magnetospheres ofthe Earth and of Jupiter.

In the case of the Earth magnetosphericswarm, it is visualised that more than eightspin-stabilised micro-satellites, each ofabout 50 kg, will be placed at key positionswithin the Earth’s magnetosphere. Althoughthese spacecraft will require only looseformation control to ensure appropriateseparation, some developments are neededin key technology areas identified inTable 5.2.1.1. In particular, the swarmdeployment and maintenance of the inter-spacecraft distances over potentially smallseparations, down to less than 1 km, needcareful consideration. The level ofcooperation between these spacecraftdepends on the final number in the swarm.A shepherding spacecraft akin to the HIVE(Hub and Interplanetary VEhicle) formerlyconsidered in an ESA feasibility study for aMain Belt asteroid mission, might wellhandle deployment as well as commandand control.

6766


Technology Comment

Inter-spacecraft control GNC/autonomy depending on orbits

Highly integrated plasma payload Low-resource instrument suite

Radiation hardening of LEO spacecraft Radiation tolerant micro-satellites

Electromagnetic cleanliness tools Simulation and test tools

Swarm deployment system Depends on required orbits

Table 5.2.1.1: Technologies required for a magnetospheric swarm in Earth orbit.

LAYOUT3 11/3/05 4:33 PM Page 67

The exploration of the magnetosphere ofJupiter is just one of a number of differentthemes addressing different scientificobjectives within a Jupiter explorationprogramme. This will involve multiplespacecraft using common facilities andunderpinning technologies, as described inSections 5.1.3 and 5.2.2. All power for theprogramme is currently based on low-intensity low-temperature (LILT) solar arraytechnology with solar concentrators, ratherthan radioisotope thermoelectricgenerators (RTGs). Nevertheless, an RTGdevelopment remains desirable for theJupiter exploration programme and wouldbe essential for the other outer planetsbeyond Jupiter.

A small multi-spacecraft constellation withtrajectories that migrate through thecomplex system of the Jupitermagnetosphere will build on pastexperience in Earth orbit with Cluster, andpossibly with the Earth magnetosphericswarm described above. It is envisaged thattwo relay satellites, JRS1/2, needed for thefirst phase of the Jupiter explorationprogramme would contain amagnetospheric payload, while a part of theJupiter polar orbiter (JPO) would be alsodedicated to such studies (Fig. 5.2.1.1). Afourth spacecraft, the Europa orbiter (JEO)described in Section 5.1.3, would completethe constellation during its tour through theJovian system. Technologies specific to thesemicro-satellites in their magnetospheric roleare identified in Table 5.2.1.2.

Beyond the magnetospheric studies of theEarth and Jupiter, the long-term plasmaprogramme involves two extremes: thestudy of the Sun at polar latitudes at adistance of 0.5 AU, with a solar polarorbiter (SPO; Fig. 5.2.1.2) and reaching theheliopause out at 200 AU with aninterstellar heliopause probe (IHP). Boththese tools require spacecraft that canacquire an extremely large change invelocity. This can be achieved through thedevelopment of solar sailing as the baselinepropulsion system. Solar sails utilise themomentum of the photons of sunlight toobtain a very low but persistentacceleration. Since no propellant is used, thepropulsion system is very effective, althoughvery large structures are needed. Theacceleration of a solar sail spacecraft willgreatly increase as it travels closer to the

Figure 5.2.1.1: Three small spacecraft including two relaysatellites (JRS 1/2) plus a Jupiter polar orbiter (JPO) wouldcarry identical plasma payloads to form a smallconstellation to study the complex magnetosphere of theJovian system.

Technology Comment

Mass memory Size depends on orbits required


Radiation-robust micro-satellites Radiation levels depend on orbits

Power system RTG trade-off required depends on spacecraft lifetime and orbits

In system deployment Depends on orbits and science required

Autonomy To limit ground control costs

Table 5.2.1.2: The additional technologies required for the development of a smallmagnetospheric constellation within the Jovian system.

LAYOUT3 11/3/05 4:33 PM Page 68

Sun. IHP in particular will capitalise on thiseffect by first performing two solar flybysdown to 0.25 AU to obtain the requiredacceleration to travel to the heliopause at200 AU in a realistic journey time of perhaps25 years.

The development of a reliable solar sailingsystem will require great advances fromcurrent available technologies. The largestsail deployed so far has been the 20x20 mdevice in an ESA/DLR ground test. Therehave been other demonstrations as well,such as a small spinning disc saildeployment, the in-orbit solar saildeployment on the Russian Progressvehicle, and a recent JAXA deployment on asounding rocket. To turn concepts of theSPO and IHP into realistic projects, severalaspects of solar sail technologies willrequire development, coupled to atechnology-demonstration mission in Earthorbit, GeoSail, along the lines of the SMARTprogramme. Such a mission might be ableto combine an in-orbit technologydemonstration as part of a wider sciencemission such as the Earth magnetosphericswarm described earlier in this section.

The key technologies specific to the SPOspacecraft and payload are summarised inTable 5.2.1.3. Some other spacecrafttechnologies such as heatshields will bederivatives of the significant investment inthe Solar Orbiter mission.

The second science application of thispropulsion technology would be to studythe interface between the interstellarmedium and the heliosphere by means of

an interstellar heliopause probe. To reach200 AU within 25 years would require a250x250 m x 1 µm sail with characteristicacceleration of 1.1 mm/s2, and sail assemblyloading of 3.9 g/m2. The minimum distanceto the Sun is currently set at 0.25 AU, which

6968


Technology Comment

Sail material with Al/Cr coating 2 µm-thick film, loading 8 g m–2

Sail degradation Material thermal and radiation effects

Sail deployment system ~150 x 150 m2 sail

Spacecraft – sail jettison system

Lightweight booms

Sail guidance navigation and control Spacecraft autonomy

Highly integrated payload Low-resource instrument suite

Table 5.2.1.3: The technologies required for the development of the Solar Polar Orbiter based ona solar sail propulsion system.

Technology Comment

RTG ~8 W/kg

GNC and autonomy Autonomous navigation

Analogue-Digital Coverter System Control of large sails

High-temperature sail material 1 µm with Al/Cr coating

Degradation of sail material Characterisation of candidate materials

Deep-space communications RF versus optical

Sail sensor integration Autonomous navigation, health monitor

Long-life components Applies to all subsystems


Table 5.2.1.4: The technologies required for the development of the Interstellar HeliopauseProbe based on a solar sail propulsion system.

Figure 5.2.1.2: The Solar Polar Orbiter with its large sailstowed prior to deployment (left). The fully deployedsystem (right) allows for a payload mass of 25 kg to bedeployed to study the polar regions of the Sun. Inset: thefinal orbit achieved 0.5 AU above the poles of the Sun.

LAYOUT3 11/3/05 4:33 PM Page 69

implies that the sail will have to withstand asolar flux 16 times greater than at the Earth.The solar sail will be jettisoned at 5 AU, afterabout 5 years, during which time it isimportant that it keeps its opticalproperties, since the accelerationperformance is directly dependent on thereflectivity of the sail material. Clearly, thefulfilment of solar sail technology will be amajor challenge in the latter half of theCosmic Vision 2015-2025 timeframe.

The power system for the interstellarheliopause probe will most likely employan RTG.

The key technologies specific to theinterstellar heliopause probe for both thespacecraft and payload are summarised inTable 5.2.1.4. These are also relevant to oneof the fundamental physics explorers,contemplated in Section 5.3.1 for testinggravity at very large distances.

5.2.2 The giant planets and theirenvironments

The study of the giant planets is essentialfor understanding our Solar System andother planetary systems. The proposedJupiter exploration programme needs tobe made in a coherent and systematicmanner. This would involve a series ofmultiple spacecraft entering the systemover a number of years. To reduce risks andcosts, the programme could consist ofsmall spacecraft with very lowrequirements of mass and power, enablingthe use of relatively low-cost launchersystems. Achieving this result will call forhighly miniaturised and integrated systemsboth for the spacecraft and for theirpayloads.

Within this proposed Jupiter explorationprogramme, it is assumed that a dedicatedmini-satellite Jupiter polar orbiter (JPO) ina low orbit would provide a remote-sensing study of the giant planet’satmosphere. Moreover, in situmeasurements would be obtained throughthe injection of a number of microprobesinto the atmosphere (Fig. 5.2.2.1). These

Figure 5.2.2.1: A potentialdesign of a microprobedeployed from a localaerobot for probing in situthe atmosphere of Jupiter.The microprobe’s payloadmight consist oftemperature, pressure andlight-level sensorstogether with infraredflux, wind profile andchemistry instruments.Clearly, the final designwill be governed by theprobe depth required.

Technology Comment

Thermal protection system Jupiter atmospheric entry is extremely challenging

Microprobe injection system Depends on orbit and science

Microprobes including possible Capable of withstanding Jovian atmosphericmini-aerobot conditions (P, T) depending on required

depth

Miniaturised microprobe payload Requirement is science-dependent

Low-resource communication system Mission profile-dependent. It should enable communications during the entire entry sequence

Table 5.2.2.1: The technologies required for the Jupiter polar orbiter and probes.

Figure 5.2.1.3: The Interstellar Heliosphere Probe in itslaunch configuration, with the booms and huge solar sailstowed (left). The sail is jettisoned (right) after 5 years at5 AU from the Sun. Thereafter, the probe travels out fromthe Solar System to reach the heliopause in 25 years, andthen on into interstellar space.

LAYOUT3 11/3/05 4:33 PM Page 70

could be injected directly from the orbiter,which would require a thermal protectionsystem for each microprobe, or else bereleased from a mini-aerobot (e.g. a glideror a solar Montgolfier balloon) deployedfrom a single entry probe capsule The latteroption would require considerableresources for the aerobot and introduce asingle-point failure for all probes.

A Jupiter relay mini-satellite (JRS2) is againassumed to handle communications and tocontribute to the magnetosphericconstellation described in Section 5.2.1.Apart from the technologies discussed inSections 5.1.3 and 5.2.1, specifictechnologies for the JPO and probes aresummarised in Table 5.2.2.1.

5.2.3 Asteroids and other small bodies One of the keys to understanding thehistory and composition of our SolarSystem lies in investigating its small bodies,such as asteroids and comets. Retrieving asample from a small, low-gravity body anddelivering it to Earth for detailed analysis issignificantly different from obtaining aplanetary sample. A Mars sample returnmission, for example, will require a landerwith a fully controlled entry and descentsystem, and a launcher to send the samplesinto space. Retrieving a sample from a smallbody should be simpler (Table 5.2.3.1). Adedicated launch vehicle after samplecollection is not necessarily required forsuch a low-gravity environment, and thedescent requirements are also significantlydifferent. It may be possible to consider thecollection of samples from multiple sites onan asteroid, or even from multiple targets.

Near-Earth asteroids are easily accessibleand make attractive targets for a small-body sample return project (Fig. 5.2.3.1).Their orbital lifetimes are short compared tocosmological timescales and they arecontinuously being replenished from othersources, either from the main asteroid beltor from comets. The goal of a near-Earthobject sample return is to collect ascientifically significant harvest of thesurface material of one or more asteroidsand deliver it to Earth.

It is envisaged that a small spacecraftdispatched on a Soyuz-Fregat 2B launchvehicle (or equivalent ‘low-cost’ launcher)will rendezvous with one or more near-Earth asteroids, perform remote sensingobservations and ultimately initiate a seriesof sampling manoeuvres. Upon completionof sampling, the spacecraft will return toEarth, where the sample canister will makea direct Earth entry.

The amount of material that can be broughtback will influence the science that can be

7170


Technology Comment

Sample mechanism Touch-and-go multi-site sampler

Sample-transfer mechanism Transfers sample from sampling device to Earth entry vehicle

Earth entry vehicle Planetary protection

Guidance and navigation system Highly autonomous, capable of site recognition and course correction during sampling

Table 5.2.3.1: The technologies required for a near-Earth object sample return mission.

Figure 5.2.3.1: The near-Earth sample return spacecraft inorbit about an asteroid (left). The spacecraft trajectory torendezvous with two near-Earth asteroids (Nerus andBivoj) is also shown (right). Detailed mission analysis willbe required to optimise the targets and route.

LAYOUT3 11/3/05 4:33 PM Page 71

performed. Most analytical instrumentsrequire much less than a gram of material,and the others only a few grams. However, agreater amount is needed to get a goodoverview of the sampled area. Someredundancy is also necessary and thereshould be some additional material in casefurther research is desired. The objectivewould therefore be to collect a few hundredgrams from each sampling site. Onceobtained, the samples will be transferredinto a canister inside an Earth entry vehicle(EEV) (Fig. 5.2.3.2).

Several studies have already examinedpotential designs of entry vehicles for Marssample return missions. These could help inthe design and development of the EEV forthe asteroid mission.

Section 2.3 mentions the long-term aim of

exploring the small bodies of the Kuiperbelt, beyond Neptune. Such a project isbeyond the scope of Cosmic Vision 2015-2025, yet some of the technologies to bedeveloped for other purposes would clearlybe relevant, most specifically those requiredfor the interstellar heliopause probe(Section 5.2.1).

5.3 Theme 3: what are the fundamentalphysical laws of the Universe?

Fundamental physics became well-embedded in ESA’s space science andtechnology with the adoption of the bigESA-NASA LISA mission to look forgravitational waves. That aspect reappearslater in this section, in a discussion of LISA’ssuccessor, but there are many other ways ofchecking the fundamental physical lawswith smaller space projects.

Figure 5.2.3.2: A sample-and-return vehicleperforming a touch-and-go manoeuvre on anasteroid (top left).A possible overallspacecraft configurationwith propulsion andsampling stage togetherwith the Earth entryvehicle are shown at topright. Schematics of theEarth Entry Vehicle arealso shown (lower panels).

LAYOUT3 11/3/05 4:33 PM Page 72

5.3.1 Explore the limits of contemporaryphysics

Unlike Solar System exploration orastronomy, fundamental physics typicallyrequires spacecraft in purely gravitationalorbits. That is to say, drag and spuriousacceleration effects must be minimised,implying the need for an on-board drag-free control system, comprising an inertialsensor, a charge-control system, a low-thrust propulsion system and drag-freecontrol software. For the candidate projectsin the Cosmic Vision 2015-2025 timeframe,two categories of such spacecraft areenvisaged. One comprises a series of small,standard, low-cost spacecraft in low-Earthorbit forming the core of a fundamentalphysics explorer programme(Section 5.3.1.1). The second categoryconsists of individually-designed spacecraft,or even several spacecraft flying information in special orbits or trajectoriesoptimised to achieve their scientificobjectives. Examples of these, directed totesting gravity at long ranges, appear inSection 5.3.1.2.

5.3.1.1 The fundamental physics explorerprogramme

Many fundamental physics experiments canbe carried out in the weightlessness ofspaceflight with an accuracy order ofmagnitude higher than in ground-basedlaboratories or on the International SpaceStation. The optimum environment forthese experiments would be on-board ahighly stable 3-axis stabilised, drag-freeplatform. The fundamental physicsexplorer programme would be based on astandard platform that would be reused for

7372


Figure 5.3.1.1: The principle of a cold-atom source. Atomsare trapped by a combination of a magnetic field andlaser beams. The lasers are adjusted such that the thermalmomentum of the trapped atoms is reduced.

Parameter Ground Limit Space Requirement

Free evolution time < 80 ms 5 < t < 100 s

Measurement time < 100 ms up to 100 s

Temperature Typically 100 nK pK to fK

Dynamics Trap frequencies > 1 Hz 0.01 < f < 1 Hz

Trapped condensate size 100-500 µm 100 µm < L < 10 mm

Table 5.3.1.1: Expected improvements in parameters through the use of Bose-Einsteincondensates in space in the Fundamental Physics Explorer Programme.

several missions in low-Earth orbit with onlyminor modifications in order to reduce theprocurement cost. The platform could havethe following general features:

— 3-axis stabilised spacecraft with drag-free control;

— low-vibration environment withoutmoving parts (e.g. body-mounted solararray instead of deployable units);

— Sun-synchronous, low-altitude (500-700 km) circular orbit;

— limited total mass to allow for anoptimised launch vehicle;

— mission lifetime typically 1 year.

Several candidate experiments envisage theuse of a Bose-Einstein condensate (BEC),which is an ideal gas of identical particlessharing a single quantum state – in effect, asuper-atom. Only recently pioneered on the

LAYOUT3 11/3/05 4:33 PM Page 73

ground, BECs give a unique insight into abroad range of phenomena in fundamentalphysics, as well as offering prospects fornew quantum sensors based on matter-wave optics. Add the benefits of ‘lowgravity’ and a calm environment in space,and the BECs will become even moreamazing.

Table 5.3.1.1 summarises the expectedimprovements in various experimentalparameters when experiments areperformed in space. Clearly, space-qualifiedBEC systems will be an importantunderpinning technology for manyexperiments in fundamental physics, andwill set the stage for innovative studies,such as:

— phase transitions at ultra-lowtemperatures (pK–fK range);

— dipolar quantum gases;— physics of ultra-dilute quantum gases,

excitations in the weak trappingregime;

— quantum gas mixtures in a microgravityenvironment;

— quantum decoherence;— high-resolution interferometry with

coherent matter waves (atom laser).

Fig. 5.3.1.1 shows the technique used toachieve a BEC, using lasers in combinationwith a strong magnetic field. The absolutetemperature of the matter waves has to be

low (< nK), and needs to be controlled veryaccurately (fK range) by Raman coupling,which requires the development of space-qualified Raman lasers with high stability.Integration by nanotechnology wouldsignificantly increase the robustness, whileallowing a reduction in the requiredcurrent, and better cooling.

Here, some of the candidates for thefundamental physics explorer programmeare briefly considered. All except the first ofthese examples require BECs; relevanttechnologies are listed in Table 5.3.1.2.

Test of the equivalence principle usingmacroscopic objectsThe equivalence principle, that everythingfalls at the same rate under gravity, is testedby a set of proof masses that are in free-fallaround the Earth in a drag-free satellite.Disturbances need to be minimal, andtherefore the test masses are in a cryogenicenvironment, well-shielded from strayelectromagnetic fields.

Test of the equivalence principle usingbeams of cold atomsUsing BECs as the samples under test and amatter-wave interferometer as themeasurement device, the equivalenceprinciple could be tested with a variety ofdifferent atomic species. Such anexperiment would yield similar levels ofaccuracy to those of a macroscopic

LAYOUT3 11/3/05 4:33 PM Page 74

measurement (as in the first example), butwould be complementary in extending themeasurement to microscopic scales.Additionally, a possible spin-gravity couplingcould be investigated.

Searches for deviations from Newtoniangravity at small distancesThis would require a specially designedmatter-wave interferometer where theatomic trajectories of one arm pass close toa probe mass. The gravitational force felt bythe atomic wavepackets is translated by theatom interferometer into a phase shift in theoutput port of the instrument. By a space-based experiment involving very slow atomsand long interaction times, the effect ofsmall-distance gravity could be measured tomicron scales. The same technology as forany matter-wave interferometer would berequired (Fig. 5.3.1.2), but the extremely slowatoms represent a further development intechnology.

Test of the gravitational inverse squarelaw at several large rangesThis experiment would use a matter-waveinterferometer with a BEC as source, in theform of a gravity gradiometer. The essentialmission requirement would be to place thedrag-free spacecraft in a highly elliptic orbitso as to measure the Earth’s gravity fieldover a wide range of distances. (For anotherpossible gravitational experiment, outsidethe explorer programme, seeSection 5.3.1.2).

Cold-atom clocks of very high precisionThe performance of atomic clocks can beimproved in space, using cold atoms.

Weightlessness allows very long interactiontime between the atoms and the probingelectromagnetic field, while the lowtemperature improves both the accuracyand the stability of the instrument. Meanshave to be found, both aboard thespacecraft and at the ground station, totransmit the time signal to ground withoutintroducing further uncertainties in thetime reference. Correcting for thegravitational shift will require precise orbitdetermination, to the cm range or better.For the readout of the clock, frequencytransitions need to be phase-stabilised by fslaser with 300 MHz to GHz compared to10–15 Hz optical frequency, therebygenerating a frequency comb.

7574


Figure 5.3.1.2: Principle of a matter-wave interferometer. The atomic beam passes through a laser, where momentum isadded or subtracted depending on the quantum states of the atoms. The suitable orientation of the laser beams allows thecontrol of these atomic waves such that two split beams are routed through separate paths, and recombined. At therecombination point, the atomic beams interfere, thereby the resultant phase-shifts can be measured, which reflectdifferences in the processes that affected the split beams.

Technology Comment

Cryogenic accelerometers Superconducting test masses and readout (SQUIDs)

Magnetic shielding Extremely low stray fields

Cold-atom source Robustness and reliability, low power,lightweight; atom chips

Low-noise cold-atom source Various elements, e.g. Cs, Rb, H, Mg, Ca, Sr,Ag, Xe, I

Bose-Einstein condensate High level of integration and nanotechnology

Atom traps Tight traps, smaller than the de Broglie wavelength; box-shaped potential wells where atoms can be free-floating

Atom laser Independent cooling and trapping, chip-based atom source, for high brightness

Ultra-stable lasers Low-amplitude and frequency noise,accurate beam-shaping

Ultra-stable microwave source For laser control and frequency combs

Ultra-stable Raman lasers High-frequency stabilisation for narrow atomic transitions

Table 5.3.1.2: Technologies for the fundamental Physics explorer programme.

LAYOUT3 11/3/05 4:33 PM Page 75

Investigation of possible time-dependenceof fundamental physical constantsUsing high-accuracy clocks based on coldatoms, and by excitations of narrow atomictransitions, the stability of an atomictransition can be measured. This relatesdirectly to the fine-structure constant α,which defines the strength of theelectromagnetic force. Measurements underdifferent conditions, or with changes ingravity, should reveal any time-dependenceof α.

Tests of quantum measurement theory(entanglement and decoherence)To investigate decoherence, the transition ofquantum matter with its statistical behaviour

to matter as perceived in daily life, a high-intensity matter-wave would be released totravel over large distances in anundisturbed manner. The BECs must consistof at least 105 atoms. Compensating formagnetic fields will be also necessary, tobetter than 1 µG over 1 m. The sametechnology can be used for measurementsof entanglement.

5.3.1.2 Checking the strength of gravity atlong ranges

An anomalous small but constantfrequency drift was observed in thetracking data of NASA’s Pioneer 10 and 11probes, consistent with an extraacceleration towards the Sun of9x10–10 m/s2. This might indicate abreakdown of Newton’s law of gravity atlarge distances and, by implication,Einstein’s general relativity. Motivated bythese observations, a conceptual missionof the fundamental physics explorer seriescould be a deep space gravity probethat would aim to achieve free-fall(geodesic) motion for a test mass in theSolar System over a distance range from5 AU to 70 AU, and to monitor this motionprecisely with an acceleration resolutionof 10–12 m/s2. If achieved, such a missionwould surpass the precision of currentdata by a factor of 1000, provided thatX-band and Ka-band ranging and range-rate measurements can deliver anaccuracy of the spacecraft’s position toless than 1 m (< 1 µm/s for range-rate) inthree dimensions. Thrust manoeuvres ofall kinds must cease at 5 AU, which rulesout planetary flybys at Jupiter andbeyond.

Technology Comment

Phase-locked high power laser 100 W at 1 µm

Large-area mirror based on new Low-mass system. > 1 mmaterials

High-sensitivity drag-free control Noise < 10–16 m s–2 Hz–1/2

system

Next-generation inertial sensors C-couple proof mass

High-precision pointing system High-quality GNC to 10–6

over 105 km

Low-frequency GNC FEEP thrusters and control

Table 5.3.2.1: The technologies required for the development of a gravitational wave cosmicsurveyor.

Technology Comment

Large collecting lens Large Fresnel lens

Compact fast photodetectors High time resolution and low power/heat consumption

Table 5.3.1.3: Technology themes for a space detector for ultra-high-energy cosmic rays.

LAYOUT3 11/3/05 4:33 PM Page 76

The deep space gravity probe might beaccomplished by solar sailing, which couldprovide an initial high velocity. In thisscenario, the propulsion phase ends withthe shedding of the solar sail at 5 AU.Thereafter, the spacecraft will release proofmasses of about 5 kg each, which willperform the actual measurement. Theseobjects will be fully passive withhomogeneous surfaces, such that theeffects of solar pressure and of dustparticles can easily be modelled. The free-fall of the proof masses will be monitoredvia laser ranging by the main craft, whichwill also carry all necessary communicationand power generation equipment.

5.3.1.3 Detection of ultra-high-energycosmic rays

Matter accelerated to extremely highenergies also arrives in the Earth’s vicinity.Apart from the commonplace cosmic raysin the 1010 eV range, there are astoundingcosmic ray particles above 1019 eV, morethan a million times more powerful thananything produced by accelerators on theground. If they hit the Earth, they createvery extensive showers of particles andmake the atmosphere glow by fluorescenceand Cherenkov radiation.

Ground facilities, including the large Augerarray in Argentina, observe the extensive airshowers from the ground, but they arelimited by the local horizon. A spacedetector for ultra-high-energy cosmicrays looking down from low Earth orbitcould witness the events around a muchlarger swath. It would need a large-aperturetelescope and sensitive light detectors in

the near-ultraviolet and blue region of thespectrum. Table 5.3.1.3 comments briefly onthese topics.

5.3.2 The gravitational wave UniverseThe search for gravitational waves comingdirectly from the Big Bang is rated as highlyimportant within Theme 3, but the proposedgravitational wave cosmic surveyor willnot be easily achieved before the end of theCosmic Vision 2015-2025 timeframe. Themost favourable frequency band for thedetection of the Big Bang’s gravitationalradiation is 0.1-1 Hz, which is well outsidethe mHz waveband of the ESA-NASA LISAantenna due for launch around 2014.

Fig. 5.3.2.1 illustrates the 5 million kmtriangle to be marked out by the three LISAspacecraft, and their successive positions asthey orbit the Sun in the Earth’s wake. Veryslight changes in the great distancesbetween the spacecraft, measured with laserbeams, will reveal passing gravitationalwaves.

For the next-generation space antennas,tuned to the 0.1-1 Hz range, the spacecraftseparation will be significantly smaller.Clearly, the technologies will build on theLISA mission, and again use a constellationof spacecraft flying in a very extendedformation. Key technologies required areidentified in Table 5.3.2.1.

7776


Figure 5.3.2.1: The successive year-round positions of thethree spacecraft of the ESA-NASA LISA mission (2014),which will trail the Earth in its orbit around the Sun. Veryslight changes in the 5 million-km separations, measuredwith laser beams, will reveal passing gravitational waves.

LAYOUT3 11/3/05 4:33 PM Page 77

5.3.3 Matter under extreme conditionsHere, the requirement is for a large-aperture X-ray observatory to probe thehot gas very close to a black hole, withgood spectral and temporal resolution. As

this tool is also needed under Theme 4 ‘Howdid the Universe originate and what is itmade of?’, the technology is addressed inSections 5.4.2 and 5.4.3.

5.4 Theme 4: How did the Universeoriginate and what is it made of?

The art of the telescope maker hasgradually extended the range of humanvision out to the limit of the observableUniverse, taking us in time-machine fashionalmost back to the very beginning. Butthere obscurity sets in, because of dust andionisation, and even large objects look smalland confusable in the sky. New generationsof telescopes in space are needed toimprove the view.

5.4.1 The early UniverseThe study of the early Universe centres onthe role of dark energy and inflation.Investigations of dark energy could beaccomplished through the luminosity-redshift relation of supernovae Type 1a for alarge-enough range of redshifts. Anotherapproach is to study the effect of weaklensing – the bending of light by agravitational field produced by a large-scalematter distribution in the Universe.Precision measurements of both of theseeffects require a space-based wide-fieldoptical-infrared imager, usingtechnologies identified in Table 5.4.1.1.

The sensitivity of any such spaceobservatory will depend on the aperture ofthe primary mirror which, with currenttechnology, is limited by the launchershroud and particularly by the mass

Technology Comment

Deployable mirror system Low mass, large aperture

High-stability optical bench Low mass in stable environment

Large deployable sunshade Low-mass system

Active optics Lightweight smart optics at ~1 arcsec

Closed-cycled coolers Long life

Large-area near-infrared/optical Large-format arrays + readouts sensors

Table 5.4.1.1: The technologies required for the development of a wide-field optical-infraredimager.

Technology Comment

Deployable antennae Low mass, large aperture


Closed-cycled cooler Long life

Polarisation-sensitive sensors Large-format arrays and readout

Table 5.4.1.2: The technologies required for the development of an all-sky cosmic microwavebackground polarisation mapper.

Technology Comment

Deployable grazing incidence mirror Low mass, large aperture


Grazing-incidence mirror coatings Optimised reflectivity

Formation-flying Metrology and control laws

Closed-cycled low-temperature cooler Long life and low temperature

Wide-field semiconductor sensors Large-format arrays

Cryogenic sensors Medium-format arrays

Table 5.4.2.1: Technologies needed for development of the large-aperture X-ray observatory.

LAYOUT3 11/3/05 4:33 PM Page 78

constraints. The development of a large,low-mass deployable mirror system with ahigh resolving power would be required.The imaging performance of such a systemwill depend on the thermo-mechanicalstability of the optical bench carrying theoptics (active system). A large primarymirror will impose a commensurateincrease in the dimensions of other opticalcomponents. The optical bench thereforewill be crucial for ensuring the stability ofthe overall optical system. The focal planedetector of such a wide-field imagerrequires giga-pixel arrays coupled to thedevelopment of low-noise CMOS sensorsapproaching CCD-type performance.

An advantage of the operation of suchwide-field imaging optics in space is thepossibility of operating the mirror at thediffraction limit, should this be requiredscientifically. However, an importantfeature is the stability of the image pointspread function from one observation tothe next on the same field. In order toexploit this capability, it will be essential tominimise the relative pointing error andpointing drift of the spacecraft through theparallel development of a high-precisionattitude control system. Such a controlsystem would have considerably widerapplications within the Cosmic Visionprogramme.

Considering the role of inflation in theearly Universe, observing the polarisationproperties of the cosmic microwavebackground is one of two approaches forcharacterising the primordial gravitationalwaves assumed to be left over from the Big

Bang. It requires a multi-frequency all-skycosmic microwave backgroundpolarisation mapper with much highersensitivity than Planck will achieve. Keytechnologies required are identified inTable 5.4.1.2.

The second approach will be to look for theactual gravitational waves from the BigBang at frequencies around 0.1-1 Hz, whichare uncluttered by more local sources. Thisgravitational wave cosmic surveyor wasdiscussed in Section 5.3.2.

7978


Figure 5.4.2.1: The assembly of high-precision siliconwafers into a pore optics stack from which a mirror petalof about 1 m is constructed. Many such petals form thelow-mass deployable mirror system needed for a large-aperture X-ray observatory.

Figure 5.4.2.2: The two spacecraft of the large-apertureX-ray observatory (left). The large mirror spacecraft (MSC)and its 10 m deployable mirror system are in thebackground; the smaller detector spacecraft (DSC) is inthe foreground. The separation between spacecraft will becontrolled to ~ 1 mm by the DSC. Deployment will be atL2 (right).

LAYOUT3 11/3/05 4:33 PM Page 79

ambitious goals of the large aperture X-rayobservatory to be achieved.

It is clear that such a huge mirror systemwith a collecting area of > 10 m2 at 1 keV, awide field of view, and a resolution of betterthan 5 arcsec is a major technologychallenge, involving novel mirror designwith advanced materials. Such a single-aperture mirror system will necessitate along focal length (~50 m) implyingformation-flying of two spacecraft: a mirrorspacecraft and a detector spacecraftseparated by the focal length. Fig. 5.4.2.2shows such a possible configurationdeployed at the second Lagrangian pointL2.

The need for precision formation-flying oftwo or more spacecraft is a common themethrough a number of potential astrophysicsmissions in Cosmic Vision 2015-2025. In asimilar fashion, payload items, includinghigh-stability optical benches and low-temperature closed-cycle coolers, becomesupport technologies of a generic nature.

In addition to such an X-ray facility, anotherdeep-Universe observatory will be requiredto resolve the far-infrared extragalacticbackground light into discrete sources andlocate the 50% of the star-formation activityin the Universe hidden by dust, to resolvestar-formation regions in nearby isolatedand interacting galaxies, and to identifyspectroscopically the cooling of molecularclouds with primordial chemicalcomposition. These goals require afar-infrared observatory to have anangular resolution of about 1.5 arcsec at200 µm. The major technical challenge willagain involve the development of a large-

Technology Comment

Deployable mirror system Low mass, large aperture, 10 kg/m2



Active optics Smart structures operable at low temperatures

Formation flying Metrology and control, with the ability to fillan interferometric u,v plane

Closed-cycled cooler Long life

Far-infrared sensors Large-format superconducting direct detection arrays

Tunable coherent THz receivers Broadband array receivers approaching quantum-limited performance

Table 5.4.2.2: The technologies required for the development of an far-IR facility.

5.4.2 The Universe taking shapeHere, the aims are to map cosmic historyback to the time when the first luminoussources ignited, and to trace thesubsequent evolution of galaxies and theirsupermassive black holes, together withtheir effects on the intra-cluster medium.The necessary tool is a large-apertureX-ray observatory that is over two ordersof magnitude more powerful than currentfacilities. Timely deployment is essential tomaximise the synergies with the LISAgravitational wave observatory, notably inlocating the mergers of supermassive blackholes expected to be detected by LISA. Thekey technologies required are identified inTable 5.4.2.1.

Clearly the key to such a mission is thedevelopment of a high-resolution large-aperture mirror system. Fig. 5.4.2.1 showsjust how such a mirror made up of manymirror petals can be fabricated. These high-precision pore optics based on siliconwafers are a European breakthroughtechnology, which would allow the

LAYOUT3 11/3/05 4:33 PM Page 80

extremely rapid variations in emissions, asnoted in Table 5.4.3.1.

Sources of explosive nucleosynthesis andelectron-positron annihilation are also ofmajor interest. Building on the current ESAIntegral mission, the need will arise for agamma-ray imaging observatory that willcontinue to explore with unprecedentedsensitivity the region from 50-2000 keV. Itwill probably need to rely on diffractiveoptics with a long focal length. Novelreflective optics could potentially also beused in the region 50-200 keV. Such anobservatory will require the developmentof formation-flying spacecraft similar tothose required for the X-ray observatory,but with an order-of-magnitude increase inthe focal length. The key technologiesrequired are identified in Table 5.4.3.2.

aperture deployable mirror system. Keytechnologies are identified in Table 5.4.2.2.Particular effort will be required in thedevelopment of the far-infrared sensors.

5.4.3 The evolving violent UniverseThe study of the evolving violent Universeinvestigates the role of accretion andejection mechanisms taking place in thevicinity of black holes and neutron stars, andthe crucial interplay between black holesand galaxy evolution. It aims at probingdeep inside the gravitational well of blackholes and neutron stars, providing athorough test of general relativity in thestrong field limit, and deals with the physicsof strong interactions in ultra-denseenvironments, the virulent processes inhypernova explosions leading to gamma-raybursts, and binary black hole mergers. Thesephenomena will best be studied at X-raywavelengths through the development of alarge-aperture X-ray observatory asdescribed in Section 5.4.2, but with specialattention to the technologies for detecting

8180

Technology Comment

High time-resolution sensors Rates > 1 MHz and resolution ~1 µs

Precision clocks Absolute local time to 100 ns

Higher energy mirror systems Layered synthetic microstructures

High-energy X-ray semiconductors Imaging arrays

Spectropolarimeters High sensitivity

Table 5.4.3.1: The technologies required for the development of an X-ray facility focused on the X-ray temporal properties.

Technology Comment

High-energy focusing optics High-efficiency photon collection

Large-aperture deployable optics Mass-efficient deployment system

Long-baseline formation-flying Metrology and control over ~1 km

High-energy gamma-ray Imaging array and ASIC readoutsemiconductors

High-energy reflective coatings Layer synthetic microstructure

Table 5.4.3.2: Technologies required for the development of a gamma-ray imagingobservatory.

Figure 5.4.3.1: A gamma-ray imaging observatory basedon two formation-flying spacecraft separated by 0.5 km(top). The very large-aperture focusing system usesdiffractive optics possibly based on the Laue lens principle(bottom) and would study the gamma-ray emission, bothspectral and temporal, from matter under extremeconditions of gravity.

LAYOUT3 11/3/05 4:33 PM Page 81

Taking account of the scientific andtechnological perspectives of Chapters 1 to5, we now develop possible strategies thataddress the four top questions of CosmicVision 2015-2025 with candidate conceptsfor missions. Appropriate space tools areproposed within each of the selected areaswhere big progress can be expected in thenext two decades. In some cases, the sameitem appears in more than one scientificcontext and this obviously enhances itscross-disciplinary value. We also give a fewpreliminary indications of how theproposals might be sequenced within thetimeframe of Cosmic Vision 2015-2025.

6.1 A strategy for Theme 1: stars,planetsand life

An intellectually stimulating feature of thepresent efforts to answer the question‘What are the conditions for planetformation and the emergence of life?’ is thatthey bring to an end a long period in whichresearch on planets seemed to be entirelydistinct from stellar and galactic astronomy.Now the aim is to treat the Solar System asa prime exhibit in the much broadercontext of stellar and planetary formation,aiming at a new science of comparativeplanetology.

In the early stages of Cosmic Vision 2015-2025, a Near-Infrared NullingInterferometer could be set out to identifyEarth-like planets orbiting other stars byfinding telltale molecules in theiratmospheres. An ingenious interferometrictechnique using multiple spacecraft wouldsuppress the bright rays from a parent star

Chap

ter6

LAYOUT3 11/3/05 4:33 PM Page 82

to let its faint planetary companions showthemselves sufficiently for spectrographicanalysis (Section 1.2).

For in-depth analysis of terrestrial planetswithin the Solar System, Mars remains anearly target, especially in view of thesuccess of Mars Express and the initiation ofESA’s Aurora Programme. Examining theplanet’s surface in greater detail by MarsSurface Exploration, including the use ofdrills and rovers, and eventually by a MarsSample Return would be fitting taskswithin Cosmic Vision 2015-2025, as well as,of course, the Aurora Programme(Section 1.3).

Another important aspect of habitability isthe characterisation of the magneticenvironment. The Sun's magnetic fieldcould be charted by a Solar Polar Orbiter(Section 1.3).

The births of stars and planets remainslargely mysterious because the events areshrouded in dust. Visualised for the middleof the 2015-2025 period, a Far-InfraredObservatory would use a large telescopemirror, kept in shape by ‘smart’ active optics,to penetrate the dust and observe the birthevents in much greater detail than everbefore (Section 1.1).

Some Earth-sized planets will be discoveredif and when they pass between us and theirstars, dimming them slightly, but a fullcensus requires detection of theircontributions to stellar wobbles, by ultra-high-precision astrometry surpassing thatof ESA’s Gaia. A purpose-built Terrestrial

Planet Astrometric Surveyor would take acomplete census of the roughly Earth-sizedplanets circling other stars, out to 100 pc, ormore than 300 light-years (Section 1.2).

Jupiter’s fascinating moon Europapossesses a subsurface ocean that makes itthe next best candidate, after Mars, toharbour alien life in the Solar System. Toexplore it, a dedicated Europa Orbiterand/or Lander would be a strongcandidate for inclusion in a Jupiter

8382

Proposed Strategies and Their

Implementation

What are the conditions for planet formation and the emergence of life?

First In-depth analysis of terrestrial planets

Search for Earth-like exo-planets with a Near-Infrared NullingInterferometer with high spatial resolution and low-resolutionspectroscopy

Explore Mars by Mars Landers and Mars Sample Return

Next Understand the conditions for star, planet and life formation

Trace the formation of stars and exo-planets with a Far-InfraredObservatory with high spatial and low to high spectral resolution

Pursue the question of the stellar magnetic environment necessaryfor life to occur and survive, with a 3-D solar magnetic field explorer– Solar Polar Orbiter

Later Make a census of Earth-sized planets

Detect small planets orbiting stars within 100 parsecs of the Sun,with a Terrestrial Planet Astrometric Surveyor

Explore Jupiter’s moon Europa as a possible place for life

Include a dedicated Europa Orbiter and, if possible, Europa Landersin a Jupiter Exploration Programme (JEP)

Finally Image terrestrial exo-planets

(beyond 2025) To see an Earth-sized planet of another star will require a LargeOptical Interferometer

Table 6.1: Proposed strategy for Theme 1

LAYOUT3 11/3/05 4:33 PM Page 83

Exploration Programme (JEP). A landerwould need to penetrate the icy surface ofthe moon deeply enough to find nutrientsor surviving chemical traces of life, if theyexist (Section 1.3).

6.2 A strategy for Theme 2: the best-known stellar system

In the cross-disciplinary spirit of explorationadopted for Cosmic Vision 2015-2025, thequestion ‘How does the Solar System work?’now bears upon our investigations of theplanetary systems of other stars, and theenvironments available for life. Makingbetter sense of the complex behaviour ofplasmas in the interplanetary environment

is also essential for improving ourunderstanding of the Universe at large, theordinary matter of which is almost entirelycomposed of plasmas of many kinds.

Our own planet’s space environment, wherethe magnetosphere fights dramatic battleswith the solar wind, provides an excellentnatural laboratory for plasma physics. Anearly aim would be to create an EarthMagnetospheric Swarm consisting ofeight or more micro-satellites orbiting theplanet in changeable partnerships, to trace the plasma events on much smallerscales than attempted hitherto(Section 2.1).

Comprehensive exploration of the Sun’smagnetic bubble, the heliosphere, is alsoenvisaged. Within it, the solar wind blowsoutwards from the Sun’s atmosphere to farbeyond the realm of planets, and disturbsthe Earth as it passes. After a century ofwork on solar magnetism, the fundamentalsremain elusive. So does the wish to makereliable long-term predictions of Sun-Earthinteractions. A Solar Polar Orbiter wouldcircle over the north and south poles of theSun at half the Earth-Sun distance, enablingsolar physicists to chart the magnetic fieldsproperly at the visible surface near thepoles, for the very first time (Section 2.1).

Jupiter, together with its space environmentand moons, continues to invite closerinspection of what is, in effect, a SolarSystem in miniature. The plasma physics ofa huge, rapidly-rotating magnetosphereinteracting with the solar wind, and alsowith local sources of matter, is challenging.

How does the Solar System work?

From the Sun to the edge of the Solar System

First Examine plasma processes through the full hierarchy of scales in theEarth’s magnetosphere with an Earth Magnetospheric Swarm

Next Chart the 3-D magnetic field at the Sun’s visible surface using aSolar Polar Orbiter

Finally Send an Interstellar Heliopause Probe towards the outer reachesof the heliosphere

Giant planets and their environments

First In a Jupiter Exploration Programme, examine the Jovianenvironment, including the moon Europa, using a series of multiplemicro-spacecraft

Then Explore the hidden Jovian atmosphere with Jupiter Probes and thesurface of Europa with a Europa Lander

Asteroids and other small bodies

First For analysis on the Earth, obtain material from a primitive type ofasteroid, by a Near-Earth Object Sample Return project


LAYOUT3 11/3/05 4:33 PM Page 84

Better knowledge of the planet itself willhelp astronomers to make sense of the ‘hotJupiters’ that they see orbiting close toother stars. The interest of astrobiologists inJupiter’s moon Europa was mentioned inSection 6.1.

With the general aim of improving ourunderstanding of the giant planets andtheir environments, we envisage a JupiterExploration Programme. It could consist ofmission concepts using multiple micro-spacecraft, to be sent into orbit aroundJupiter itself and the moon Europa. Greatengineering challenges in a harshenvironment are balanced by the promiseof rich scientific rewards. Within aframework of international collaboration,launches towards Jupiter and Europa wouldoccur at intervals through much of theperiod 2015-2025 (Sections 2.1 and 2.2).

The Jupiter programme also calls for probesof highly original kinds. Jupiter Probeswould plunge deep into the opaqueatmosphere of the planet, in a number ofselected regions, to send back surerinformation about the gas giant’s internalcomposition and circulation (Section 2.2).Hopefully, a Europa Lander could beincluded too, although the technicalproblems are severe (Section 5.2).

An Interstellar Heliopause Probe wouldmake a 25-year journey out to 200 timesthe Sun-Earth distance, in order to reachand explore the frontier where the solarwind of the heliosphere is finally halted bythe thin gas that fills the spaces betweenthe stars. The interstellar medium could

then be sampled directly for the first time(Section 2.1).

Solar sails would be the innovative methodof propulsion employed to put the SolarPolar Orbiter into its difficult pathperpendicular to the plane of the Earth’sorbit, and also to propel the InterstellarHeliopause Probe on its long pilgrimage. Toprovide experience with solar sailing, asmall technology mission could be neededearly in the post-2015 period.

Completing the Solar System strategy areprojects to gather samples from otherworlds, including an asteroid, and returnthem to the Earth so that scientists cananalyse the materials in their well-equippedlaboratories. That was done fruitfully withthe lunar samples returned by the USApollo and Soviet Luna programmes. ANear-Earth Object Sample Return shouldtarget one of the most primitive asteroids(carbonaceous-type) passing close toEarth’s orbit. Success would bring additionalknowledge of the small building blocks ofthe Solar System to put alongside theresults from the comets investigated in pastand present ESA missions (Section 2.3)

6.3 A strategy for Theme 3: let’s rewritephysics textbooks

Never before has the interplay beenstronger between theories of thefundamental forces and particles of thecosmos and, on the other hand, theobservations of their handiwork in cosmicspace. The Big Bang at the birth of theUniverse, gamma-ray bursts of great

8584


LAYOUT3 11/3/05 4:33 PM Page 85

violence, and supermassive black holes thatpower the fireworks of active galaxies – suchphenomena bring space scientists face-to-face with big issues in fundamental physics.The observed conditions far surpassanything within reach of laboratoryexperiments, and the question ‘What are thefundamental physical laws of the Universe?’still evades a clear answer. Fortunately, theencounters between fundamental physicsand space science are not confined todistant astrophysical events.

Europe has the chance to take the initiativein opening up a completely new field ofscientific research, by sending into spacenovel technologies based on experimentswith ultra-cold atoms and Bose-Einsteincondensates, where swarms of atoms behavelike single super-atoms. In experiments ofultra-high precision, impossible on theground, Europe’s physicists want to explorethe limits of contemporary physics, lookingfor any flaws in the fundamental theoriesdeveloped in the 20th Century that mayopen the door to the most profounddiscoveries of the 21st Century.

To this end, it is proposed to initiate aFundamental Physics ExplorerProgramme in the 2015-2025 timeframe. Weenvisage low-cost missions, using a standardtype of drag-free and vibration-free satellites,to carry into space a variety of cold-atominstruments that promise incredibly precisemeasurement, timing, tracking and pointing(Section 3.1).

So many excellent experiments of this kindhave already been proposed by the physicscommunity that selection will not be easy.One general aim is to examine the small-scale nature of space and time, on whichtheoretical physics rests. Another is the wishto explore the fuzzy boundary between theeveryday human-scale world and thesub-atomic realm of quantum mechanics –where ‘entangled’ particles are linkedinstantaneously across great distances, andyet on the other hand the quantum systemseventually ‘decohere’ and give way to normalmacroscopic behaviour. The physicists alsowant to look for clues that may help to pin

What are the fundamental physical laws of the Universe?

Explore the limits of contemporary physics

First For a Fundamental Physics Explorer Series develop a sequence ofinexpensive small missions using the same platform, designed forultra-high-precision experiments that exploit cold atoms and othernovel technologies, for which proposals include: testing the natureof space and time; exploring the limits of quantum theory(entanglement, decoherence); looking for signs of quantum gravity

Later Exploring Solar System gravity for violations of Einsteinian (andNewtonian) gravity at long ranges with a view to resolvinganomalies in the tracking of Pioneer-10 with a Deep Space Gravity Probe

Later Begin particle physics in space with a Space Detector for Ultra-High-Energy Cosmic Rays

The gravitational wave Universe

Later Make a key step towards detecting gravitational waves from theBig Bang with a Gravitational Wave Cosmic Surveyor operating ina new frequency window (0.1-1.0 Hz) with orders of magnitudemore sensitivity than LISA

Matter under extreme conditions

Probe black holes and ultra-high-energy particle physics

First Black holes and neutron stars with a Large-Aperture X-rayObservatory


LAYOUT3 11/3/05 4:33 PM Page 86

down a quantum theory of the force ofgravity, which has preoccupied manytheorists for the past 30 years.

If gravity is truly a quantum force, thenEinstein’s general relativity cannot beexactly correct. The Pioneer Anomaly hintsat a possible flaw: NASA’s Pioneer-10 probehas travelled a little more slowly thanexpected on its way out of the SolarSystem. A custom-designed Deep SpaceGravity Probe could investigate whetherthis anomaly really exists; does the inverse-square law of gravity fail over largedistances? We hope that such a conceptcould be implemented in the latter part ofthe 2015-2025 timeframe.

Black holes and neutron stars provide otherexamples of matter under extremeconditions, owing to the overwhelmingeffects of gravity in collapsed objects.Fundamental physics would have much tolearn from a Large-Aperture X-rayObservatory, which could be expectedearly in the 2015-2025 period. It wouldprobe gas very close to black holes andexamine neutron stars in great detail.

If extreme conditions beyond human reachare likely sources of new physics, the mostimportant tool imaginable just now wouldbe a means of observing directly theextravagantly fierce events in the Big Bangitself. A Gravitational Wave CosmicSurveyor could make a huge step towardspenetrating the fog of charged particlesthat creates the cosmic microwavebackground at the limit of visibility for light-like rays, but hides what happened earlier.

As gravitational waves can pass freelythrough the matter, they should reveal whatwas going on during the first moments ofthe Big Bang. But their detection calls forinstruments operating at frequencies quitedifferent from those of other gravitational-wave experiments, whether existing orunder development. A European system inthis key waveband would be feasible by2025. Operating on its own, it would detectevery individual gravitational wave sourcein this band in the entire Universe, returninga wealth of information about the earlyformation of galaxies and stars. Workingwith international partners, and developingthe technology even further, several LISA-like arrays operating together would finallypenetrate the fog and see the Big Bangdirectly for the first time (Section 3.2).

We also draw attention to the opportunitythat arises to study particle physics fromspace with a Space Detector for Ultra-High-Energy Cosmic Rays. Later in thedecade, this would complement the largeground-based arrays that register theextensive flashes of light produced whencosmic particles of astounding energy hitthe atmosphere in their vicinity.

6.4 A strategy for Theme 4: homing in onthe cosmological action

Overlapping with the intense interest in thehidden details of the Big Bang is the effortof astronomers to answer the question‘How did the Universe originate, and what isit made of?’ Observatories in space may bethe only means of finding out what reallyhappened in the so-called Dark Ages of the

8786


LAYOUT3 11/3/05 4:33 PM Page 87

cosmos, meaning the first billion years or soafter the Big Bang, beyond the limit ofvisibility for present instruments.

The very first gravitationally-boundstructures assembled in the Universe – theprecursors to today’s galaxies, groups andclusters of galaxies – are scarcely known. Tofind them and to trace the subsequentco-evolution of galaxies and supermassiveblack holes would be a prime task for a

Large-Aperture X-ray Observatory.Besides detecting these very earlyaggregations of matter (Section 4.2), thisinstrument would also detect and chart theentire course of our violent Universe,including the origin of the chemicalelements of which planets and living thingsare built (Section 4.3). Its role in probingultra-strong gravitational fields was notedin Section 6.3.

Space telescopes are also needed to revealmore clearly the machinery of theexpansion of the Universe. A Wide-FieldOptical-Infrared Imager would explore theacceleration of the cosmic expansion andthe dark energy that drives it, both by theeffects of weak gravitational lensing bylarge early masses, and by the detection ofvery remote supernovae (Section 4.1).

To investigate the earliest phases of theorigin of the Universe, including aninflationary episode very early in the BigBang scenario, a new approach is needed.This relies on gravitational waves releasedprimordially, which must have affected thepolarisation of the radiation in the cosmicmicrowave background. An All-Sky CosmicMicrowave Background PolarisationMapper could therefore trace theprimordial gravitational waves indirectly(Section 4.1). Later, these primordial wavesshould be directly detectable by thedemanding technology of theGravitational Wave Cosmic Surveyoralready cited Section 6.3.

A Far-Infrared Observatory was noted inSection 6.1 as a means of observing the

How did the Universe originate and what is it made of?

The early Universe

First Explore the acceleration of the cosmic expansion and the DarkEnergy that drives it, both by effects of weak lensing and by thedetection of very remote supernovae, with a Wide-Field Optical-Infrared Imager

Investigate the inflationary phases in the evolution of the Universeby indirectly detecting primordial gravitational waves with anAll-Sky Cosmic Microwave Background Polarisation Mapper

Later Directly detect the primordial gravitational waves from the Big Bangwith a Gravitational Wave Cosmic Surveyor

The Universe taking shape

First Find the first gravitationally-bound structures and trace thesubsequent co-evolution of galaxies and supermassive black holeswith a Large-Aperture X-ray Observatory

Later Resolve the sky background into discrete sources and trace the star-formation episodes hidden by dust absorption with a Far-InfraredObservatory

The evolving violent Universe

First Examine the accretion process of matter falling into black holes andtrace the life cycle of chemical elements in stars, galaxies and theintergalactic medium with a Large-Aperture X-ray Observatory

Later Continue this work and also understand in detail the history ofsupernovae in our Galaxy and in the Local Group with aGamma-Ray Imaging Observatory


LAYOUT3 11/3/05 4:33 PM Page 88

birth of stars and planets in our own Galaxy.It would have a very important cosmologicalrole too, in tracing the evolution of theearliest masses by resolving the far-infraredbackground into discrete sources, and byrevealing the star-formation activity hiddenby dust absorption (Section 4.2).

To support the detailed examination ofblack holes by the Large-Aperture X-rayObservatory, and also aiming to understandin detail the history of supernovae in ourGalaxy and in the Local Group of galaxies,we envisage a Gamma-Ray ImagingObservatory, which may be feasibletowards the end of the 2015-2025 period(Section 4.3).

6.5 Implementing the Cosmic Vision2015-2025 space science plan

The breadth of the investigationsrepresented in the strategies outlined aboveis enormous. They range from the poles ofthe Sun to the birth of the Universe, andfrom gigantic cosmic structures to sub-atomic particles. Also remarkable is the waythat very different techniques converge onthe same question, whether it be the originof life or the fundamental physics of thecosmos that makes our existence possible.

Science priorities and programme prioritiesare not identical. A highly desirablecandidate mission may be postponed fortechnological and/or budgetary reasons.The different themes and their associatedprojects interact with one another. Somespace tools are relevant to more than one ofour scientific questions, and overlaps also

occur in the new technologies that need tobe developed.

Certain groups of projects require similarinnovations, such as the formation-flyingforeseen for several telescopes and self-organising associations of micro-satellites inSolar System missions. On the other hand,work towards devising instruments using thenovel cold-atom technologies, and adaptingthem to spaceflight, should probably beginnow, with a view to being ready for the firstFundamental Physics Explorer. The same istrue of the optics and detectors for X-rayastronomy, a European excellence peak. Solarsailing will take time to master, and so itsapplications may be deferred until relativelylate in the 2015-2025 period.

The space tools nominated in the fourstrategies should be seen as candidateconcepts for missions. More ideas arementioned than those affordable in the2015-2025 timeframe. Exactly how much canbe accomplished will depend on the Level ofResources of the Science Programme, butalso, in part, on what internationalcollaborations can be arranged. However,competition between the candidateconcepts is bound to persist up to the timeof selection and approval.

Flexibility must remain in the space scienceprogramme to allow for unforeseenopportunities or difficulties, whether in thescience or in the technology. The readinessof the technology – often highly innovative –will be a decisive factor in the selection andsequencing of the eventual missions. ESAwill also wish to maintain a decade-by-

8988


LAYOUT3 11/3/05 4:33 PM Page 89

decade balance between Solar Systemresearch, astronomy and fundamentalphysics, and to safeguard Europe’sreputation as a reliable partner ininternational collaborations.

On the basis of the scientific prioritiespresented in this document, werecommend that ESA’s Science ProgrammeExecutive issues a succession of Calls forMission Proposals to implement CosmicVision 2015-2025. The pace ofimplementation should provide for long-sustained, confident work by scientificinstitutes and industry, which by traditionhas enabled Europe to excel in its chosenspace science projects despite budgetarylimitations.

Implementation could proceed in three‘slices’, each providing for several launchesduring a period of 3-4 years. This approachleads to a policy of corridor planning.Flexibility within each slice will depend onthe size, number and sequence of missions,and on the financial and technical payoffs

from international cooperation. The activityfor each slice will grow and later decline,over the decade and beyond, whileavoiding peaks or troughs in the overallannual expenditures.

An example of such phased corridorplanning for three slices is shown in theabove diagram, which at the time of writingis only illustrative. As the diagram alsomakes plain, the rate of earlyimplementation of the new plan will bemuch affected by the envelopes of actualexpenditure on the last major missions ofHorizon 2000 Plus, namely Gaia,BepiColombo, JWST, LISA and Solar Orbiter.

If the first major mission of Cosmic Vision2015-2025 is to be launched in 2015, itshould be under construction (Phase-B) by2008 at the latest. Allowing time for teamsto prepare their proposals, and for Phase-Astudies and approval to proceed in 2007,the first Call for Mission Proposals ought tohappen early in 2006.

LAYOUT3 11/3/05 4:33 PM Page 90


9190

ESA’s corridor planning for three programme slices.

LAYOUT3 11/3/05 4:33 PM Page 91

This document, Cosmic Vision 2015-2025,exposes the big scientific questions to beaddressed by Europe’s space science. Itproposes the long-term plan that Europeneeds in order to remain at the forefront ofspace science and to improve on theheritage of COS-B, Giotto, Huygens andXMM-Newton, among all other sciencemissions developed by ESA in its first30 years. In the tradition of Horizon 2000(1984) and Horizon 2000 Plus (1994-1995),Cosmic Vision 2015-2025 takes its strengthfrom the massive response by the scientificcommunity to ESA’s Call for Themes, issuedin April 2004. It has been prepared from theinputs of the space science community bythe full ESA science advisory structure – theAstronomy Working Group, the SolarSystem Working Group, the FundamentalPhysics Advisory Group and, at the end, theSpace Science Advisory Committee, assistedby ESA’s Science Directorate.

For a space science mission, a developmenttime of 10-15 years, preceded by long andintense preparatory work, is the rule. Suchan investment cannot be sustained byscientists, technologists, national fundingagencies, space industry and internationalpartners without the existence of ESA’slong-term plan. The one given here is thelogical continuation, into the next decade,of previous ESA science planning cycles. Allactors on the European space stage relyheavily on these long-term plans to buildconfidence in the success of projects thattake two decades to develop.

Our plan addresses four broad questions ofthe utmost importance to understand the

Chap

ter7

LAYOUT3 11/3/05 4:33 PM Page 92

Universe and mankind’s place in it. Youngscientists and aspiring students areespecially fortunate to be living at a timewhen answers to such basic questions maybe within their grasp. What are theconditions for planet formation and theemergence of life? How does the SolarSystem work? What are the fundamentalphysical laws of the Universe? How did theUniverse originate and what is it made of?Chapters 1 to 4 propose ways of answeringthese questions and possible space tools tobe developed to tackle them. Chapter 5 liststhe technology challenges that are raisedand suggests the necessary technologydevelopment programme. Chapter 6suggests possible implementationstrategies.

To implement Cosmic Vision 2015-2025, it issuggested to ESA’s Science Programme toissue Announcements of Opportunities formissions in the coming years. Indeed, forthe first mission of the plan, to be launchedin 2015, the first Call for Mission Proposalsought to happen early in 2006 if theconstruction phase is to start by 2008 at thelatest. It should be noted that some of therequired tools to answer a specific questioncan probably be fulfilled as a singleinstrument on a mission. Others will requirea full mission development and yet a fewmore will require a full programme to bedefined.

In parallel to all of the above, as outlined inChapter 5, ESA will have to make substantialefforts on key technological developments,in the frame of its Technology DevelopmentPlan, to make Cosmic Vision 2015-2025

feasible. Crucial technologies have alreadybeen identified in that chapter that in somecases will benefit several themes. Theseinclude lightweight mirror optics, formationflying, autonomous deployment of a swarmof micro-satellites, solar sailing andradiation-tolerant lightweight components.Substantial progress has been made onsome of these technological developmentsunder ESA’s Payload and AdvancedConcepts Office and needs to be activelycontinued to meet a realistic schedule. In allcases, key technological developments arenecessary before missions can beconsidered for implementation.

We have not explicitly addressed the all-important question of what will have to bedone to analyse and exploit scientificallythe veritable flood of data to be generatedby Cosmic Vision 2015-2025. Already withthe current generation of orbitingobservatories and probes, ESA and nationalinitiatives are, jointly in some cases,organising ad hoc centres and services. Anorder-of-magnitude increase in the dataanalysis effort will be required into the nextdecade, with many missions entering theTerabyte information flow. It goes beyondthe scope of the present document toaddress this issue in detail. However, wewant to draw attention to it and werecommend that Europe take promptinitiatives to ensure that the science returnof the programme be commensurate withESA’s programmatic effort.

Our plan will be placed in the framework ofthe worldwide space science context, takinginto account possible synergies and

9392

Conclusions

LAYOUT3 11/3/05 4:33 PM Page 93

collaborations with science programmesfrom ESA’s international partners (theUnited States’ NASA, the Japan AerospaceExploration Agency (JAXA), the RussianRoskosmos, the Indian Space ResearchOrganisation (ISRO), the Chinese SpaceAgency, etc.). Indeed, European spacescience has a long tradition of collaborationwith NASA, with which some of the mostsuccessful missions have been developed(Hubble Space Telescope, SOHO, Ulysses,Cassini-Huygens) and others are beingdeveloped for the 2005-2015 decade (JWST,LISA). A very close collaboration with JAXAwill happen for the first time with theBepiColombo mission to Mercury andcollaboration with the Chinese SpaceAgency was inaugurated with the DoubleStar mission. Even the most successful ESA-only missions (Giotto, Hipparcos, XMM-Newton, Cluster, Integral, Mars Express,Rosetta, Venus Express, Planck, Herschel,Gaia and Solar Orbiter) have someinvolvement from international partners.

Cosmic Vision 2015-2025 should alsocontinue to mesh creatively with thenational space science and technologyprogrammes in ESA’s Member States.Furthermore, several countries in theenlarged European Union that have not yetjoined ESA are already participating,through valued co-investigators, in ESA’sscience missions. They and all other EUmembers will obviously be welcome toparticipate in our new long-termprogramme.

Within Europe, there are other importantcultural, scientific and technological

partners with which constructiveinteractions along the lines of this plan haveto be thoroughly explored. The EuropeanSouthern Observatory (ESO), for example, ispushing ground-based astronomy to thelimit. Techniques pioneered at its bigobservatories in Chile, includinginterferometry at visible wavelengths, willsooner or later be transferred to spaceprojects. Also directly relevant to thefundamental physics in Cosmic Vision 2015-2025 is the experimental and theoreticalwork of the European Organisation forNuclear Research (CERN) in Geneva. Its LargeHadron Collider is due to be switched on in2007. Experiments on quark-gluon plasmas,for example, produced by colliding nuclei oflead atoms, are complementary to ESA’sinvestigations of ‘matter under extremeconditions’ in the natural laboratories ofneutron stars.

Within ESA itself, added strength andcreativity will be gained by the interactionof the science programme with ESA’soptional programmes, most notably the‘Aurora’ Programme, and other moreapplication-oriented programmes.

ESA’s Science Programme is also a strongsupporter of European space industry. Asmuch as 80% of ESA’s space science budgetis channelled, directly or indirectly, toEurope’s aerospace industry, and thisrepresents a massive investment intechnological innovation. Industrialengineers have played a highly creative partin implementing Horizon 2000 (1984) andHorizon 2000 Plus (1994-1995), puttingunrelenting effort into novel hardware and

LAYOUT3 11/3/05 4:33 PM Page 94

software and finding ingenious solutions tothe difficulties expected in the hostileenvironments of space. In a word, spaceengineers enjoy the unprecedentedchallenges that space science repeatedlythrows up. With every novel tool requiredfor ESA’s Science Programme, thetechnological competence of Europe’sspace-related industries will grow.

Above all, Cosmic Vision 2015-2025 is beingpresented to the new European SpaceCouncil in the context of the institutionalEuropean Union presence in spaceactivities. In the European Commission’sWhite Paper Space: A New European Frontierfor an Expanding Union (November 2003),space science is described as ’essential toEurope’s identity and leadership as aknowledge-based society’. The Commissionalso notes that the recent erosion offunding for ESA’s space science programmehas reached a point where it disrupts thebalance of the programme and misses thechance to optimise costs and flexibility. TheWhite Paper calls for ’urgent correctiveaction’.

Our plan is presented as an act ofconfidence by a vast and multi-facetedcommunity, who gladly collected in it theirbest ideas and confidently expects toobtain the necessary support for the timelyimplementation of an exciting programmeaimed at responding to the White Papercall. How much of the promising projectspresented in Cosmic Vision 2015-2025 canbe accomplished will, naturally, depend onthe Level of Resources of the ScienceProgramme.

Last but not least for the future of Europe,ESA’s successes in space science is toencourage students to pursue studies andcareers in science and engineering. Theprogramme also helps to stem a potentiallydisastrous brain-drain of scientific andengineering talent to the USA and otherparts of the world with active spaceprogrammes.

For their part, the European space sciencecommunity and the ESA ScienceProgramme Executive pledge theircontinuing effort for the maintenance andreinforcement of Europe’s leadership inspace science. With the enthusiasm of aspace industry which, among many otherachievements, has taken us to Saturn and toits moon Titan, this is the right way ofrealising a knowledge-based andcompetitive Europe.

9594


LAYOUT3 11/3/05 4:33 PM Page 95

Space science gives modern society awindow on the infinite. Althoughastronomy from the ground and work inEarth-bound laboratories have their partsto play in decoding how our planet wasformed out of the cosmos, indeed how wecame to be, only in space can we observewithout the disruption of our atmosphereright across the electromagnetic spectrum.Only in space can we experiment outsideEarth’s gravitational pull and, of course, onlyby travelling through space can weinvestigate directly other parts of our SolarSystem.

This document is proof, if proof wereneeded, that European scientists have a‘Vision’ worthy of the epithet Cosmic. Witheyes tuned by a knowledge of what ourtechnical potential can be, the scientistswho wrote it start from the peak of presentscientific understanding of where we areand, from there, look ahead to a vista of theterritories for exploration that lie before usand what is doable. It lays out whatscientific questions remain and the pathsthat need to be followed to obtain answers.

The key, the fundamental driver to theprogramme proposed, is very simple andcan be expressed as ‘Science for the sake ofscience’; in Latin, ‘Scientia gratia scientiae’.Translated back into English, one wouldhave ‘Knowledge for the sake of knowledge’. Ascience-based society is a knowledge-based society. A strong programme forexploring the Universe should be part ofEurope’s ‘Lisbon agenda’ to become theleading knowledge-based society on theplanet.

Aft

erw

ord

LAYOUT3 11/3/05 4:33 PM Page 96

What is proposed here is not just idlecuriosity. What is remarkable at this point isthat very basic questions, simple questionsthat everyone can understand, that scientistswould have put on one side a few decadesago, now are coming centre stage for study.Are we alone in the Universe? Why is theUniverse the way it is? What is special aboutthe Earth? What were the critical features indetermining Earth’s habitability (and howlong may it remain so)? The discovery in thelast decade of extra-solar planets hasopened a new perspective and newquestions. But it is not just from astronomythat the advances of the last decade or sohave come. The reopening of planetaryexploration, both Earth’s neighbours and thegiant planets in the outer Solar System, hasprovided a cornucopia of issues for researchand speculation. This is truly a great time tobe a space scientist.

Does Europe deserve such a vision? Thisquestion is not one for the scientists toanswer. For centuries, Europe did lead theworld in astronomy and it has recentlyregained that lead with the EuropeanSouthern Observatory’s telescopes in Chile.Could Europe also lead in exploring theUniverse from space? Technically, it is clear itcould; financially, things need to change.European space industry has shown itself upto the most extreme challenges set by thescientists so far. The scientists show herewhat is the vision. The only issue cloudingthe speed at which the vision is realised isthe budget. The challenge is to the politicalleaders of Europe to respond in order that atleast a substantial part can be realised by2025.

For now, Cosmic Vision 2015-2025 willserve as a map of the terrain ahead to betackled by Europe’s space scientists. It isnot a firm plan. However, using the map asa guide, ESA will make priorities for long-term technology development.Nonetheless, the actual progress anddirections taken across the terrain aheadshould remain, as far as possible, in thehands of the science community. Becausethe themes will be the dominant factor, itmay well be that missions not foreseennow will materialise before long, thatmission foreseen now will vanish, that thesequences outlined here might bechanged. The themes outlined here will berealised by the community responding toa phased series of announcements ofopportunity. This process, constrained bythe budgets available in years to come,will eventually give birth to the actualmissions that will build the programme.After a competitive phase, during whichseveral missions will be studied in paralleland the technological requirements willbe examined, selected missions willemerge. Probably, as has proved effectivein recent years, missions will be groupedto exploit commonality in technicalrequirements.

Europe will not do it alone. The map willalso serve as a guide for seeking futurecooperation with the science programmesof the other space-faring nations, such asthe USA, Russia, Japan, China, India andCanada. Europe has a greater GrossDomestic Product than any of these and itshould aspire to a leading role at theinternational level.

9796


LAYOUT3 11/3/05 4:33 PM Page 97

ESA’s Science Programme will not do italone. Some targets may be met using theInternational Space Station. Moreover, Marsexploration and, in the future, lunarexploration will fall under the ESA Auroraprogramme designed to provideinfrastructure that scientists can exploit.Hence the priority assigned in particularhere to Mars exploration will beaccomplished using this additionalprogramme. Similarly, the individualMember States will continue to pursuescientific missions; examples right now arethe French-led Corot (Theme 1) andMicroscope (Theme 3) missions. It is certainthat these should not be the last nationally-led missions, which will fit naturally withinthe grander plan. The challenge in bothcases will be to the national authorities toensure coherence in their investments.

These control not only the various ESAprogrammes through their ESA delegationsbut also the national programmes.

Europe’s scientists have seized the initiativeand put forward a comprehensive visionappropriate for and fit to inspire a dynamicand outward-looking society. Its realisationdepends on budget. The challenge is oncemore to the political leaders and thenational authorities of Europe to respond tomake this happen.

David SouthwoodDirector, ESA Science

LAYOUT3 11/3/05 4:33 PM Page 98

9998


LAYOUT3 11/3/05 4:33 PM Page 99

SSAC Membership(Authors of this report highlighted)

Prof. Giovanni F. Bignami (Chairman), CESR,Toulouse, France

Prof. Ester Antonucci, Istituto Nazionale diAstrofisica, Osservatorio Astronomico diTorino, Pino Torinese, Italy

Prof. Xavier Barcons, Instituto de Fisica deCantabria (CSIC-UC), Santander, Spain

Prof. Willy Benz, University of Bern,Switzerland

Prof. Peter J. Cargill, (Chair, SSWG), ImperialCollege, London, United Kingdom

Prof. Luke Drury, Dublin Institute forAdvanced Studies, Ireland

Prof. Tim de Zeeuw, Sterrewacht Leiden, TheNetherlands

Prof. Bernard Schutz, (Chair, FPAG), MaxPlanck Institute for Gravitational Physics,Golm bei Potsdam, Germany

Prof. Tilman Spohn, Deutsches Zentrum fürLuft- und Raumfahrt, Institut fürPlanetenforschung, Berlin, Germany

Dr. Catherine Turon, (Chair, AWG),Observatoire de Paris, Meudon, France

ObserversSPC Chairman: Prof. Risto Pellinen, Finnish

Meteorological Institute, Helsinki, Finland ESF/ESSC Chairman: Prof. Gerhard

Haerendel, International UniversityBremen, Germany

LPSAC representative: Dr. Frances Westall,Centre de Biosphysique Moléculaire,Orléans, France

AWG Membership

Dr. Catherine Turon, (Chair), Observatoire deParis, Meudon, France

Prof. Conny Aerts, Instituut voorSterrenkunde, Leuven, Belgium

Dr. Angela Bazzano, Istituto Nazionale diAstrofisica, Istituto di Astrofisica Spaziale,Roma, Italy

Prof. Paolo de Bernardis, Università‘La Sapienza’, Roma, Italy

Dr. José Cernicharo, Instituto de Estructurade la Materia, Madrid, Spain

Dr. Chris Done, University of Durham, UnitedKingdom

Prof. Ariel Goobar, Stockholm University,Sweden

Dr. Thomas Henning, Max-Planck-Institut fürAstronomie, Heidelberg, Germany

Dr. Rob J. Ivison, Royal Observatory,Edinburgh, United Kingdom

Dr. Jean-Paul Kneib, Observatoire Midi-Pyrénées, Toulouse, France

Prof. Evert Meurs, Dublin Institute forAdvanced Studies, Ireland

Prof. Dr. Andreas Quirrenbach, LeidenObservatory, The Netherlands

Dr. Peter Schneider, Universität Bonn,Germany

Prof. Michiel van der Klis, PannekoekInstitute, University of Amsterdam,The Netherlands

Dr. Pedro Teixeira Pereira Viana, Centro deAstrofisica-Universidade do Porto,Portugal

Dr. Werner Zeilinger, Institut für Astronomie,Universität Wien, Austria

Annex 1: Authors and

Memberships

LAYOUT3 11/3/05 4:33 PM Page 100

SSWG Membership

Prof. Peter J. Cargill, (Chair), Imperial College,London, United Kingdom

Prof. Wolfgang Baumjohann, Institut fürWeltraumforschung, Graz, Austria

Prof. Lars Blomberg, Royal Institute ofTechnology, Stockholm, Sweden

Dr. Dominique Bockelée-Morvan, LESIA,Observatoire de Paris, Meudon, France

Dr. Luigi Colangeli, Istituto Nazionale diAstrofisica, Osservatorio AstronomicoCapodimonte, Napoli, Italy

Prof. Ulrich Christensen, Max-Planck-Institutfür Aeronomie, Katlenburg-Lindau,Germany

Dr. Sarah K. Dunkin, Rutherford AppletonLaboratory, Didcot, United Kingdom

Dr. François Forget, Université Paris VI, Paris,France

Dr. Viggo Hansteen, Institute of TheoreticalAstrophysics, Univ. of Oslo, Norway

Dr. Rony Keppens, FOM-Institute Rijnhuizen,Nieuwegeln, The Netherlands

Dr. Lucia Marinangeli, International ResearchSchool of Planetary Sciences, UniversitàG. d’Annunzio, Pescara, Italy

Dr. Torsten Neubert, Danish Space ResearchInstitute, Copenhagen, Denmark

Dr. Agustin Sanchez-Lavega, Universidad delPais Vasco, Bilbao, Spain

Dr. Steven J. Schwartz, Queen Mary, Univ. ofLondon, United Kingdom

Prof. Dr. Rorbert F. Wimmer-Schweingruber,Christian-Albrechts-Universität, Kiel,Germany

FPAG Membership

Prof. Bernard Schutz, (Chair), Max PlanckInstitute for Gravitational Physics, Golmbei Potsdam, Germany

Prof. Enrico Bellotti, Universita MilanoBicocca, Milano, Italy

Dr. L. Blanchet, Institut d’Astrophysique deParis, France

Prof. Wolfgang Ertmer, University ofHannover, Germany

Prof. Dr. Gerd Leuchs, Max-Planck-Forschungsgruppe, Universität Erlangen-Nürnberg, Germany

Dr. J.A. Lobo, Institut d’Estudis Espacials deCatalunya, Barcelona, Spain

Prof. Dr. Felicitas Pauss, CERN, Geneva andETH, Zürich, Switzerland

Prof. Christophe Salomon, Ecole NormaleSupérieure, Paris, France

Dr. Michael C.W. Sandford, RAL, Chilton,United Kingdom

Dr. Henry Ward, University of Glasgow,United Kingdom

Members of the Executive involved in theCosmic Vision exercise

David SouthwoodGiacomo CavalloMarcello CoradiniHugo MaréeAnthony PeacockSergio Volonte

101100


LAYOUT3 11/3/05 4:33 PM Page 101

In response to ESA’s Cosmic Vision2015-2025 Call for Themes, 150proposals were received. Theproposals are organised in thefollowing way:

— Firstly into one of four maingroups: Astronomy andAstrophysics, Solar System,Fundamental Physics,Miscellaneous;

— Secondly, by a category withinthat group. For example, aspecific wavelength or objectclass;

— Thirdly, alphabetically bysurname within a category.

Astronomy and AstrophysicsTitle: The Formation and History of

GalaxiesProposed by: Matt Griffin et al.Contact Email:

[email protected]: Cosmology

Title: POLARIS – POLARization-basedInflation Survey

Proposed by: Per B. Lilje et al.Contact Email: [email protected]: Cosmology

Title: Unveiling the Dark Universewith a Wide-Field Imager inSpace

Proposed by: Alexandre Réfrégier et al.Contact Email: [email protected]: Cosmology

Title: Early Universe andFundamental Physics

Proposed by: Jean-Loup Puget et al.Contact Email: [email protected]: Cosmology

Title: The Emergence of the ModernUniverse

Proposed by: Joseph Silk et al.Contact Email: [email protected]: Cosmology

Title: The Birth of Stars and PlanetsProposed by: Glenn White et al.Contact Email: [email protected]: Cosmology

Title: The Hypertelescope Path –Toward Direct Images of Exo-Earths and Other Objects withMicro-arcsecond Resolution

Proposed by: Antoine LabeyrieContact Email: [email protected]: Exo Planets

Title: A Large UV-Telescope (‘Bio-UVTelescope’) for a Deep Search ofBiomarkers in Extrasolar Planets

Proposed by: Alain LecavelierContact Email: [email protected]: Exo Planets

Title: Search for Planets and Life inthe Universe

Proposed by: Alain Leger et al.Contact Email:

[email protected]: Exo Planets

Title: Astrometric Detection of Earth-Mass Planets

Proposed by: Michael PerrymanContact Email:

[email protected]: Exo Planets

Title: Understanding the PlanetaryPopulation in our Galaxy

Proposed by: Giampaolo Piotto et al.Contact Email: [email protected]: Exo Planets

Title: Chemical Evolution of Pre-Supernovae, Convection andCosmic Magnetic Fields

Proposed by: C. Catala et al.Contact Email:

[email protected]: Infrared

Title: Stars in the Darkness –Universe: Origin and Evolutionand Changing Nature of theUniverse

Proposed by: Thibaut Le Bertre et al.Contact Email:

[email protected]: Infrared

Title: The Universe at Long RadioWavelengths

Proposed by: Jean-Louis BougeretContact Email: jean-

[email protected]: Radio Astronomy

Title: ELR (European LunarRadiometers) – RadiometersOrbiting the Moon or Landed onthe Farside to Measure howRadio-Quiet the Farside of theMoon is

Proposed by: Claudio MacconeContact Email: [email protected]: Radio Astronomy

Title: The Universe at Very LongWavelengths: Opening the LastWindow of the ElectromagneticSpectrum

Proposed by: G.K. Miley et al.Contact Email:

[email protected]: Radio Astronomy

Title: The Future of UltravioletAstronomy

Proposed by: Martin Barstow et al.Contact Email: [email protected]: Ultraviolet

Title: Intergalactic MediumInvestigation and UV Astronomy

Proposed by: Jean-Michel Deharvenget al.

Contact Email: [email protected]

Category: Ultraviolet

Annex 2: Submitted Themes

for Cosmic Vision 2015-2025

LAYOUT3 11/3/05 4:33 PM Page 102

Title: The Relevance of the UVWindow for Modern Astrophysics

Proposed by: Ana Ines Gomezde Castro et al.

Contact Email: [email protected]: Ultraviolet

Title: The Future of UltravioletAstrophysics

Proposed by: Network for UltraVioletAstrophysics (NUVA)

Contact Email: aigmat.ucm.esCategory: Ultraviolet

Title: Needs for Ultraviolet Facilitiesin Astrophysics

Proposed by: Isabella Pagano et al.Contact Email: [email protected]: Ultraviolet

Title: Observational Cosmology –The Evolution of IntergalacticAbundances and of theFluctuating Metagalactic UVBackground

Proposed by: Dieter ReimersContact Email:

[email protected]: Ultraviolet

Title: Hot Stars and Supernovae asEngines and Tracers for theChemical Evolution of Galaxies

Proposed by: Klaus Werner et al.Contact Email:

[email protected]: Ultraviolet

Title: Physics of the Hot EvolvingUniverse – Science Case for aLarge European X-rayObservatory

Proposed by: Xavier Barcons et al.Contact Email:

[email protected]: X-ray and Gamma-ray

Astrophysics

Title: Gravity in the Strong Field Limitand Matter under ExtremeConditions

Proposed by: Didier Barret et al.Contact Email: [email protected]: X-ray and Gamma-ray

Astrophysics

Title: The Ultimate All-Sky Survey ofthe X-ray Sky

Proposed by: Sergio Campana et al.Contact Email:


Astrophysics

Title: Hard X- and Gamma-rayPolarization: The UltimateDimension

Proposed by: Ezio Caroli et al.Contact Email:


Astrophysics

Title: Opening a New Window toFundamental Physics andAstrophysics – Science Case foran X-ray Polarimeter

Proposed by: Enrico Costa et al.Contact Email: [email protected]: X-ray and Gamma-ray

Astrophysics

Title: MeV Gamma-Ray ScienceProposed by: Roland Diehl et al.Contact Email: [email protected]: X-ray and Gamma-ray

Astrophysics

Title: Exploring the Hard X-/Gamma-ray Continuum Sky atUnprecedented Sensitivity

Proposed by: Filippo Frontera et al.Contact Email: [email protected]: X-ray and Gamma-ray

Astrophysics

Title: The Global Star-formationHistory from X-rays: the LargeEuropean X-ray ObservatoryVision

Proposed by: IoannisGeorgantopoulos et al.

Contact Email: [email protected]: X-ray and Gamma-ray

Astrophysics

Title: Turbulence and Bulk Mass Flowin Energetic Objects: Hot PlasmaDynamics

Proposed by: Jan Willem den Herderet al.

Contact Email: [email protected]: X-ray and Gamma-ray

Astrophysics

Title: Physics behind the Long-termVariability of Interacting CompactBinaries

Proposed by: Juhani Huovelin et al.Contact Email: [email protected]: X-ray and Gamma-ray

Astrophysics

Title: Nuclear Astrophysics –Gamma-ray Spectrocopy in theMeV Domain

Proposed by: Jürgen Knödlseder et al.Contact Email: [email protected]: X-ray and Gamma-ray

Astrophysics

Title: Probing the High-EnergyUniverse

Proposed by: François Lebrun et al.Contact Email: [email protected]: X-ray and Gamma-ray

Astrophysics

Title: The Cosmological Study ofDiffuse Baryons: The Role of LowBackground Wide-Field X-rayImagers

Proposed by: Silvano Molendi et al.Contact Email: [email protected]: X-ray and Gamma-ray

Astrophysics

103102


LAYOUT3 11/3/05 4:33 PM Page 103

Title: Gamma-ray Bursts PolarisationProposed by: Nicolas Produit et al.Contact Email:


Astrophysics

Title: The Universe is Changing EveryMinute, We Just Have to Look

Proposed by: Libor Svéda et al.Contact Email:


Astrophysics

Title: Unveiling the High EnergyObscured Universe: HuntingCollapsed Objects Physics – ToPreserve the ESA Leading Role inGamma-ray Astrophysics in theNext Decade

Proposed by: Pietro Ubertini et al.Contact Email: [email protected]: X-ray and Gamma-ray

Astrophysics

Solar SystemTitle: Exobiology and

Micrometeorites: Search for theOrigin of Life

Proposed by: Santi Aiello et al.Contact Email: [email protected]: Exo Biology

Title: Search for Planetary Habitabilityin the Solar System and Beyond

Proposed by: Jean-Loup BertauxContact Email:

[email protected]: Exo Biology

Title: The Environment for Life: ACosmic Vision Theme for ESA

Proposed by: Andrew CoatesContact Email: [email protected]: Exo Biology

Title: Astrobiological Exploration ofthe Solar System and theExtrasolar Planets

Proposed by: Conseil de Groupementdu GDR CNRS Exobio

Contact Email: [email protected] or secretariate:[email protected]

Category: Exo Biology

Title: Quest for a Second Genesis ofLife

Proposed by: EuropeanExo/Astrobiology NetworkAssociation (EANA)

Contact Email: [email protected]: Exo Biology

Title: Life on MarsProposed by: Dirk Möhlmann et al.Contact Email:


Title: Lamarck: An InternationalSpace Interferometer for Exo-Lifestudies

Proposed by: Jean Schneider et al.Contact Email:


Title: The Origin and Early Evolutionof Life in our Solar System

Proposed by: Stephan Ulamec et al.Contact Email:


Title: A Sample Return Mission toNear Earth Objects

Proposed by: Antonella BarucciContact Email:

[email protected]: Near Earth Objects

Title: Search For and Investigation ofSmall Celestial Bodies for theProtection of Earth

Proposed by: Klaus J. Seidenstickeret al.

Contact Email:[email protected]

Category: Near Earth Objects

Title: Evolution of Atmospheres andIonospheres of Planets andExoplanets

Proposed by: Mats André et al.Contact Email: [email protected]: Planets

Title: Mars Exploration withEmphasis on the Ancient MartianRock Record as a Proxy for theMissing Hadean and EarliestArchaean Record on Earth

Proposed by: Archaean ConsortiumContact Email:

[email protected]: Planets

Title: Exploring Giant Planets andtheir Satellite Systems

Proposed by: Michel Blanc et al.Contact Email: [email protected]: Planets

Title: Comparative MagnetospheresProposed by: Stas Barabash et al.Contact Email: [email protected]: Planets

Title: Exploration of the outer SolarSystem Uranus Orbiter and Probe

Proposed by: Patrick CanuContact Email:


Title: Geochemical Investigation ofthe Deep Atmosphere, Surfaceand Interior of Venus

Proposed by: Eric Chassefière et al.Contact Email:


LAYOUT3 11/3/05 4:33 PM Page 104

105104


Title: Study of Atmospheric Escape,Ionospheric Physics and MagneticField on Mars

Proposed by: Eric Chassefière et al.Contact Email:


Title: Deimos Sample Return MissionProposed by: Marcello FulchignoniContact Email:


Title: Venus Interior and IonosphericOrbiters

Proposed by: Raphael Garcia et al.Contact Email: [email protected]: Planets

Title: In-Situ Exploration of PreviouslyUnexplored Planetary Surfaces(e.g Europa, Io, Titan)

Proposed by: Rob A. GowenContact Email: [email protected]: Planets

Title: European Planetary MaterialsProgramme

Proposed by: Eberhard GruenContact Email:

[email protected],[email protected]

Category: Planets

Title: The Evolution of Icy Regions inour Solar System

Proposed by: Günter Kargl et al.Contact Email:


Title: Planetary European Network ofGeophysical Observatories(PENGO)

Proposed by: Philippe Lognonné et al.Contact Email:


Title: Oxygen Circulation of PlanetaryAtmosphere and Lithosphere

Proposed by: Hans Nilsson et al.Contact Email: [email protected]: Planets

Title: Call for a Jovian SatelliteExploration Initiative with Orbitersand Landers

Proposed by: Jürgen Oberst et al.Contact Email: [email protected]: Planets

Title: In-Situ Measurements of VenusAtmosphere Properties

Proposed by: Walter Schmidt et al.Contact Email: [email protected]: Planets

Title: Planetary Surface & SubsurfaceScience

Proposed by: Wolfgang SeboldtContact Email:


Title: Exploring Mercury In-SituProposed by: Tilman SpohnContact Email: [email protected]: Planets

Title: A Multi-DisciplinaryInvestigation of the Jovian System

Proposed by: Nicolas Thomas et al.Contact Email:


Title: The exploration of the MartianSubsurface

Proposed by: Claude d’Uston et al.Contact Email: [email protected]: Planets

Title: Magnetic Clouds – A ValuableTool for Space Weather

Proposed by: A. Geranios et al.Contact Email: [email protected]: Solar Earth Connection

Title: Acceleration and Reconnectionin Near-Earth Space

Proposed by: Manuel Grande et al.Contact Email: [email protected]: Solar Earth Connection

Title: A Nano-Satellite Constellationto Study the Radiation Belts

Proposed by: Mike Hapgood et al.Contact Email: [email protected]: Solar Earth Connection

Title: Surface Research by SpacePlasma Instruments

Proposed by: Mats Holmström et al.Contact Email: [email protected]: Solar Earth Connection

Title: European Space Weather –Space Science Programme or‘Multi Space and Time Scale Solar-Terrestrial Study (M-(STS)2)’

Proposed by: François Lefeuvre et al.Contact Email: lefeuvre@cnrs-

orleans.frCategory: Solar Earth Connection

Title: Momentum Transfer from SolarWind to Planetary Rotation

Proposed by: Rickard Lundin et al.Contact Email: [email protected]: Solar Earth Connection

Title: Space Weather Fronts: Trackingand Terrestrial Response

Proposed by: Steve J. Schwartz et al.Contact Email:

[email protected]: Solar Earth Connection

Title: Helios: The Sun, The Star Closeto Earth

Proposed by: Solar and stellar physicsgroup of the Institutd’Astrophysique Spatiale

Contact Email: [email protected]

Category: Solar Earth Connection

LAYOUT3 11/3/05 4:33 PM Page 105

Title: Energetic Solar Cosmic RaySurveyor and Monitor

Proposed by: Piero SpillantiniContact Email: [email protected]: Solar Earth Connection

Title: Conjugate AuroralSpectrographic TelescopeExplorer (CASTE)

Proposed by: Johan Stadsnes et al.Contact Email:

[email protected]: Solar Earth Connection

Title: The ‘Star-Sun-Earth’ Connectionand Cosmic Magnetic Fields

Proposed by: Klaus G. Strassmeieret al.

Contact Email: [email protected]: Solar Earth Connection

Title: The Scientific Case forSpectropolarimetry from Space

Proposed by: Egidio LandiDegl’Innocenti et al.

Contact Email: [email protected],[email protected], [email protected]

Category: Solar Physics/Ultraviolet

Title: The Sun as a Particle AcceleratorProposed by: Lyndsay Fletcher et al.Contact Email:

[email protected]: Solar Physics

Title: Solar/Heliospheric Dynamicsand Magnetism

Proposed by: Maxim Khodachenkoet al.


Category: Solar Physics

Title: Solar Microscopy – Unveilingthe Sun’s Basic Physical Processesat Their Intrinsic Scales

Proposed by: Eckart Marsch et al.Contact Email:

[email protected]: Solar Physics

Title: Meteoroids and Their MeteorShowers in The Solar System: AnUnexplored Realm

Proposed by: Apostolos A. Christouet al.

Contact Email: [email protected]: Solar System

Title: SAS – A ComparativeInvestigation of the ULF-ELF-VLF(to RF) Phenomena, Its SourceActivity and Physical Backgroundon Planets, on InterplanetarySpace and the Terrestrial Effects

Proposed by: Csaba Ferencz et al.Contact Email: [email protected]: Solar System

Title: Origin of Asteroid, Comet, andOther Small Bodies

Proposed by: Yoshifumi Futaana et al.Contact Email: [email protected]: Solar System

Title: Origin and Evolution of theOuter Solar System from theComposition of Giant Planets andof Comets of the Oort cloud

Proposed by: Daniel Gautier et al.Contact Email:

[email protected]: Solar System

Title: Exploration of the Asteroid BeltProposed by: Simon Green et al.Contact Email: [email protected]: Solar System

Title: Investigation of the Kuiper beltProposed by: Harald MichaelisContact Email:


Title: Exploring Earth’s Quasi-Moonand Coorbital Companions

Proposed by: Rainer RiemannContact Email:


Title: Ice Monitoring in the SolarSystem and Elsewhere

Proposed by: Alain Sarkissian et al.Contact Email:


Title: Exoplanet Detection andCharacterisation

Proposed by: Jean Surdej et al.Contact Email: [email protected]: Solar System/Exo Planets

Title: The Formation of Our SolarSystem

Proposed by: Stephan Ulamec et al.Contact Email:


Title: Heliospheric Explorer – HEX –Beyond the Edges of the SolarSystem

Proposed by: Robert F. Wimmer-Schweingruber et al.


Category: Solar System

Fundamental PhysicsTitle: Investigation on the Origin of

Cosmic Rays with theDevelopment of a StratosphericAirship Platform for ScientificPayloads

Proposed by: Pier SimoneMarrocchesi et al.

Contact Email: [email protected]: Cosmic Rays

Title: Opening Particle Astronomy toProbe and Understand theEvolving Universe

Proposed by: Eric Plagnol et al.Contact Email:

[email protected]: Cosmic Rays

LAYOUT3 11/3/05 4:33 PM Page 106

107106


Title: Lunar Observatory for CosmicRay Physics

Proposed by: Piero Spillantini et al.Contact Email: [email protected]: Cosmic Rays

Title: Investigations of the CASIMIRForce and Vacuum fluctuations

Proposed by: Robert Bingham et al.Contact Email: [email protected]: Fundamental Physics

Title: Matter-Wave DecoherenceProposed by: Robert Bingham et al.Contact Email: [email protected]: Fundamental Physics

Title: The Role of QuantumFluctuations in Matter-WaveInterferometry

Proposed by: Robert Bingham et al.Contact Email: [email protected]: Fundamental Physics

Title: Testing General Relativity byMapping the LatitudinalDependence of the Lense-Thirring effect

Proposed by: Philippe Bouyer et al.Contact Email:

[email protected]: Fundamental Physics

Title: Interferometry with CoherentEnsembles of Atoms (ICE)



Title: Novel ‘Atom’ Optics (NAO) – ForProbing Gravity in Space



Title: Gravitational Wave CosmologyProposed by: Karsten Danzmann /

O. Jennrich et al.Contact Email:

danzmannmpq.mpg.de,[email protected]

Category: Cosmology

Title: Laser Interferometric Test ofRelativity

Proposed by: Hansjörg Dittus et al.Contact Email:


Title: Determination of the FineStructure Constant

Proposed by: Wolfgang Ertmer et al.Contact Email:


Title: Exploring Bose-EinsteinCondensates in Space

Proposed by: Wolfgang Ertmer et al.Contact Email:


Title: Ultracold Atomic Gases – Probesfor Ultralow-Energy Phenomena

Proposed by: Axel Goerlitz et al.Contact Email:


Title: Super-massive Black Holes inthe Early Universe

Proposed by: James Hough /O. Jennrich et al.

Contact Email:j.houghphysics.gla.ac.uk,[email protected]

Category: Cosmology

Title: Search for an AnomalousCoupling of the ElementaryParticle Spin to Gravity

Proposed by: Claus Lämmerzahl et al.Contact Email: laemmerzahl

@zarm.uni-bremen.deCategory: Fundamental Physics

Title: Deep Space Laser Ranging:Mapping the Solar System andProbing the Fundamental Law ofSpacetime



Title: Observation of theGravitomagnetic Clock-Effect



Title: Testing General Relativity withLong-Term Satellite Tracking



Title: NEWTON B – A Low Cost SpaceExperiment to Measure the Valueof the Universal GravitationalConstant (G) to Greatly IncreasedAccuracy

Proposed by: Roger LongstaffContact Email:


Title: A Breakthrough inFundamental Physics from Space

Proposed by: Anna NobiliContact Email: [email protected]: Fundamental Physics

Title: Search for an Electric DipoleMoment of the Electron

Proposed by: Achim Peters et al.Contact Email:


Title: Exploring Gravity in theQuantum Domain

Proposed by: Ernst M. Rasel et al.Contact Email: [email protected]

hannover.deCategory: Fundamental Physics

LAYOUT3 11/3/05 4:33 PM Page 107

Title: Ultra-Stable Clocks in SpaceProposed by: Christophe Salomon

et al.Contact Email:


Title: Ultra High PrecisionMeasurements of theEquivalence Principle

Proposed by: Michael C.W. SandfordContact Email:


Title: Search for QuantumFluctuations of Space

Proposed by: Stephan Schiller et al.Contact Email:


Title: Test of Gravity-Matter Couplingand Search for a Time-Variation ofFundamental Constants



Title: Test of Isotropy of Space forElectromagnetic WavePropagation



Title: Gödel Mission: Measuring theRotation of the Universe

Proposed by: Wolfgang Schleich et al.Contact Email:

[email protected]

Category: Cosmology

Title: Exploring Dark MatterProposed by: Bernard F. Schutz /

O. Jennrich et al.Contact Email: [email protected],

ute.schlichtingaei.mpg.de,oliver.jennrichrssd.esa.int

Category: Cosmology

Title: Search for New Short-RangeForces through a Test of theInverse Square Law of Gravitationat 1µ

Proposed by: C.C. Speake et al.Contact Email: [email protected]: Fundamental Physics

Title: Searching for the MissingBaryonic Matter

Proposed by: Stefano Vitale /O. Jennrich et al.

Contact Email:vitalealpha.science.unitn.it,[email protected]

Category: Cosmology

Title: Search for Lorentz SymmetryViolation and Spin-Spin couplingForces

Proposed by: C. Trenkel et al.Contact Email: [email protected]: Fundamental Physics

Title: Investigation of Chirality inSpace Environments

Proposed by: Jan-Erik Wahkund et al.Contact Email: [email protected]: Fundamental Physics

Title: Test of Isotropy of Space for theCoulomb Potential by Means ofMolecular Internal StateQuantum Interferometry

Proposed by: Andreas Wicht et al.Contact Email: andreas.wicht

@uni-duesseldorf.deCategory: Fundamental Physics

Title: Electron-Scale and Ion-ElectronHybrid Scale Dynamics

Proposed by: Yamauchi et al.Contact Email: [email protected]: Fundamental Physics

MiscellaneousTitle: Adaptive Grid Measurements of

Atmospheric and IonosphericParameters in Four Dimensions toStudy all Stages of Turbulence

Proposed by: Ulf-Peter Hoppe et al.Contact Email: [email protected]: Earth Observation

Title: Physics of the Earth’s UpperAtmosphere: Studies of TransientPhenomena and Long-TermClimatological Effects

Proposed by: Harri LaaksoContact Email: [email protected]: Earth Observation

Title: Establishment of a Cross-Disciplinary Earth and PlanetarySystems Laboratory

Proposed by: Hans E.F. Amundsenet al.


Category: Miscellaneous

Title: Our Laboratory MoonProposed by: Roberto Battiston et al.Contact Email: [email protected]: Miscellaneous

Title: Multi-Scale Space PhysicsProposed by: W. Baumjohann et al.Contact Email:

[email protected]: Miscellaneous

Title: A Mission to Test the PioneerAnomaly and to Probe the MassDistribution in the Nearby OuterSolar System

Proposed by: Orfeu Bertolami et al.Contact Email:


Title: Multi-Wavelength, Multi-Messenger Approach

Proposed by: Johannes BlümerContact Email: [email protected]: Miscellaneous

LAYOUT3 11/3/05 4:33 PM Page 108

109108


Title: Electromagnetic PropulsionProposed by: Remi CornwallContact Email:

[email protected],[email protected]


Title: Testing the Pioneer AnomalyProposed by: Hansjörg Dittus et al.Contact Email:


Title: Virtual Human Spaceflight: AnAlternative to Human andRobotic Mission Concepts

Proposed by: Bernard Farkin,DigitalSpace Europe



Title: Project Rama – An InterstellarProbe to Travel Beyond theHeliosphere

Proposed by: Wing-Huen Ip et al.Contact Email:


Title: Experimental Investigation ofthe Pioneer Anomaly

Proposed by: C. Kiefer et al.Contact Email:


Title: Significance of the PioneerAnomaly


@zarm.uni-bremen.deCategory: Miscellaneous

Title: In-Situ Studies as New Windowsto Astrophysics and SpaceScience

Proposed by: Ingrid Mann et al.Contact Email:


Title: Call for a Long-Lived GlobalLunar Geophysical Network

Proposed by: Jürgen Oberst et al.Contact Email: [email protected]: Miscellaneous

Title: Space Propulsion by Direct Useof the Energy of FissionFragments

Proposed by: Adinolfi Roberto et al.Contact Email:


Title: LISA Mission and the Pioneeranomaly

Proposed by: José Luis RosalesContact Email:


Title: An Artificial Moon as anExample of the Application ofPrecise ‘Second Generation’ Drag-Free Technology

Proposed by: C.C. SpeakeContact Email:


Title: Space Exploration and the NewEnlightenment

Proposed by: Ian WrightContact Email: [email protected]: Miscellaneous

LAYOUT3 11/3/05 4:33 PM Page 109

ADCS: Analogue-Digital Converter SystemALMA: Atacama Large Millimetre ArrayASIC: application-specific integrated circuitAU: astronomical unitAWG: Astronomy Working Group (ESA)

BEC: Bose-Einstein condensate

CCD: charge-coupled deviceCERN: Centre Européen de Recherches

NucléairesCMOS: complementary metal oxide

superconductorCNES: Centre National d’Etudes Spatiales (F)Corot: Convection, Rotation and Planetary

TransitsCSA: Canadian Space Agency

DLR: Deutsches Zentrum für Luft- undRaumfahrt

EDSL: Entry, Descent and Landing SystemEEV: Earth Entry VehicleESA: European Space AgencyESO: European Southern ObservatoryESRO: European Space Research

OrganisationEU: European Union

FEEP: field emission electric propulsionFPAG: Fundamental Physics Advisory Group

(ESA)

GNC: guidance, navigation & control

HIVE: Hub and Interplanetary VEhicleHST: Hubble Space Telescope

IHP: Interstellar Heliopause Probe ISO: Infrared Space Observatory (ESA)IUE: International Ultraviolet Observatory

JAXA: Japan Aerospace & ExplorationAgency

JEO: Jupiter Europa OrbiterJEP: Jupiter Exploration ProgrammeJPO: Jupiter Polar OrbiterJRS: Jupiter Relay SpacecraftJWST: James Webb Space Telescope

LEO: low Earth orbitLILT: low-intensity low-temperatureLISA: Laser Interferometer Space Antenna

MACHO: Massive Compact Halo ObjectsMicroscope: MICROSatellite à traînée

Compensée pour l’Observaton duPrincipe d’Equivalence (CNES)

NASA: National Aeronautics & SpaceAdministration (USA)

RF: radio frequencyRTG: radioisotope thermoelectric generator

SIM: Space Interferometer Mission (NASA)SOHO: Solar & Heliospheric ObservatorySPC: Science Programme Committee (ESA)SPO: Solar Polar OrbiterSQUID: superconducting quantum

interference deviceSSAC: Space Science Advisory Committee

(ESA)SSWG: Solar System Working Group (ESA)STEREO: Solar-Terrestrial Relations

Observatory (NASA)

VLT: Very Large Telescope

WMAP: Wilkinson Microwave AnisotropyProbe (NASA)

Acronyms

LAYOUT3 11/3/05 4:33 PM Page 110

cosmic vision - space science for europe 2015-2025

Documents

Transcript of cosmic vision - space science for europe 2015-2025