Contour Comet Nucleus Tour Launch Press Kit

8/7/2019 Contour Comet Nucleus Tour Launch Press Kit

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MEDIA CONTACTS

NASA Headquarters Policy/Program Management

WashingtonDonald Savage(202) [email protected]

The Johns Hopkins University CONTOUR Mission Management,Applied Physics Laboratory Spacecraft OperationsLaurel, Md.

Michael Buckley(240) [email protected]

Cornell University CONTOUR Science Team,Ithaca, N.Y. Science Data CenterDavid Brand(607) [email protected]

Kennedy Space Center, Fla. Launch ActivitiesGeorge Diller(321) [email protected]

Boeing Corporation Delta II Launch Vehicle

Huntington Beach, Calif.Larry Salazar(714) [email protected]

NASA Jet Propulsion Laboratory Navigation/Deep Space Network SupportPasadena, Calif.

Martha Heil(818) [email protected]

mailto:[email protected]














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CONTENTS

General Release ............................................................................................................................................. 5

Media Services Information......................................................................................................................... 7

Quick Facts ..................................................................................................................................................... 8

Mission Overview .......................................................................................................................................... 9

NASA Discovery Program .............................................................................................................. 16

The Science of CONTOUR ...................................................................................................................... 17

Other Comet Missions .................................................................................................................... 20

The CONTOUR Spacecraft ...................................................................................................................... 21

Spacecraft Systems and Components ........................................................................................... 24

Program/Project Management .................................................................................................................. 26



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Donald SavageHeadquarters, Washington(Phone: 202/358-1754)

Michael BuckleyThe Johns Hopkins University Applied Physics Laboratory, Laurel, MD

(Phone: 240/228-7536)

RELEASE: 02-110

NASA’S CONTOUR MISSION GETS TO THE “HEART” OF COMET DIVERSITY

Set to visit and study at least two comets, NASA’s Comet Nucleus Tour (CONTOUR) should providethe first detailed look at the differences between these primitive building blocks of the solar system, andanswer questions about how comets act and evolve.

CONTOUR is scheduled to lift-off from Cape Canaveral Air Force Station, Fla., on a three-stage BoeingDelta II expendable launch vehicle during a 25-day launch window that opens July 1 at 2:56 a.m. (EDT).The spacecraft will orbit Earth until Aug. 15, when it should fire its main engine and enter a comet-chasing orbit around the sun.

CONTOUR’s flexible four-year mission plan includes encounters with comets Encke, Nov.12, 2003, andSchwassmann-Wachmann 3, June 19, 2006. CONTOUR will examine each comet’s “heart,” or nucleus,which scientists believe is a chunk of ice and rock, often just a few kilometers across and hidden fromEarth-based telescopes beneath a dusty atmosphere and long tail.

“The CONTOUR mission will be NASA’s second mission dedicated solely to exploring these largelyunknown members of our solar system,” said Dr. Colleen Hartman, Director of the Solar System

Exploration Division at NASA Headquarters in Washington. “CONTOUR joins our other operatingmission, Stardust, which is on its way to bring a sample of a comet back to Earth, and Deep Impact willlaunch next year. These missions all help us find answers to the fundamental questions of how our planetmay have formed and evolved, and how life may have begun on Earth and perhaps elsewhere in theUniverse.”

The 8-sided solar-powered craft will fly as close as 100 kilometers (62 miles) to each nucleus, at topspeeds that could cover the 56 kilometers between Washington and Baltimore in two seconds. A 5-layer dust shield of heavy Nextel and Kevlar fabric protects the compact probe from comet dust and

debris.

“Comets are the solar system’s smallest bodies, but among its biggest mysteries,” said Dr. Joseph Veverka,

CONTOUR’s principal investigator from Cornell University, Ithaca, N.Y “We believe they hold the mostprimitive materials in the solar system and that they played a role in shaping some of the planets, but wereally have more ideas about comets than facts. CONTOUR will change that by coming closer to acomet nucleus than any spacecraft ever has before and gathering detailed, comparative data on thesedynamic objects.”

-more-



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CONTOUR’s four scientific instruments will take pictures and measure the chemical makeup of thenuclei while analyzing the surrounding gases and dust. Its main camera, the CONTOUR Remote Imager/Spectrograph (CRISP), will snap high-resolution digital images showing car-sized rocks and other featureson the nucleus as small as 4 meters (about 13 feet) across. CRISP will also search for chemical“fingerprints” on the surface, which would provide the first hard evidence of comet nuclei composition.

The targets were selected because of their diversity and relative closeness to Earth during encountertime — less than 50 million kilometers (31 million miles) — allowing astronomers to make observationsduring the encounters. Encke has been seen from Earth more than any other comet; it’s an “old” bodythat gives off relatively little gas and dust but remains more active than scientists expect for a comet thathas passed close to the sun thousands of times. Schwassmann-Wachmann 3, on the other hand, wasdiscovered just 70 years ago and recently split into several pieces, intriguing scientists with hopes thatCONTOUR might see fresh, unaltered surfaces and materials from inside the comet.

“The key to the CONTOUR mission is to visit a diverse range of comets, from an evolved comet suchas Encke, to a younger comet like SW3 or even a new comet never seen in this part of the solarsystem,” said Mary C. Chiu, CONTOUR project manager at The Johns Hopkins University AppliedPhysics Laboratory (APL), Laurel, Md. “Our mission plan gives us that flexibility.”

CONTOUR’s orbit loops around the sun and back to Earth for annual “gravity swings” toward itstargets; these maneuvers refine or revise CONTOUR’s trajectory and help it reach several cometswithout using much fuel. CONTOUR will cruise unattended between comet encounters and Earthswingbys in a spin-stabilized “hibernation” mode, helping the mission reduce operations andcommunications costs.

The $159 million CONTOUR is the sixth mission in NASA’s Discovery Program of lower cost,scientifically focused exploration projects.APL manages the mission, built the spacecraft and its twocameras. NASA’s Goddard Space Flight Center, Greenbelt, Md., provided CONTOUR’s neutral gas/ionmass spectrometer and von Hoerner & Sulger, GmbH, Schwetzingen, Germany, built the dust analyzer.NASA’s Jet Propulsion Laboratory, Pasadena, Calif., will provide navigation and Deep Space Network

(DSN) support.

Additional information about CONTOUR is available on the Web at:

www.contour2002.org

http://discovery.nasa.gov/

http://www.jhuapl.edu/

http://gsfc.nasa.gov/

http://vj-s/de/

http://www.jpl.nasa.gov/

http://www.contour2002.org/


http://vj-s/de/

http://gsfc.nasa.gov/






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MEDIA SERVICES INFORMATION

NASA Television

NASA Television is broadcast on satellite GE-2, transponder 9C, C-Band, located at 85 degrees Westlongitude. The frequency is 3880.0 MHz; polarization is vertical and audio monaural at 6.8 MHz. On July 1(launch day), television coverage will begin at approximately 1:30 a.m. EDT and continue throughspacecraft separation (scheduled for 4 a.m. EDT). The schedule of television transmissions forCONTOUR will be available on the NASA TV Web site at www.nasa.gov/ntv/.

Audio

Audio-only coverage of the launch will be available on the NASA TV voice circuits, reachable by calling(321) 867-1220, 867-1240, 867-1260 or 867-7135.

News and Status Reports

The CONTOUR News Center at Kennedy Space Center opens June 28 and can be reached at (321)867-2468. Recorded status reports will be available beginning June 28 at (321) 867-2525.

Briefings

A CONTOUR press briefing is scheduled for Friday, June 28, at 1 p.m. EDT in the KSC News Center.Panelists will discuss launch, spacecraft readiness and weather, followed by a science overview. Thebriefing will be carried live on NASA TV and the audio circuits. NASA will provide additional details asthe briefing date approaches.

CONTOUR on the Web

CONTOUR information – including an electronic copy of this press kit, press releases, fact sheets,mission details and background, status reports and images – is available on the mission Web site at

www.contour2002.org. Information on the NASA Discovery Program is available athttp://discovery.nasa.gov.

http://www.nasa.gov/ntv/







http://www.nasa.gov/ntv/



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CONTOUR QUICK FACTS

SPACECRAFT

Dimensions: 8-sided main structure; 1.8 meters (6 feet) tall; 2.1 meters (7 feet) wide

Total Weight: 970 kilograms (2,138 pounds)• Dry spacecraft and instruments: 387 kilograms (853 pounds)

• STAR-30 Solid Rocket Motor: 503 kilograms (1,109 pounds)

• Hydrazine fuel: 80 kilograms (176 pounds)

Science Instruments: high-resolution tracking imager and spectrograph; fixed visible imager; neutralgas and ion mass spectrometer; dust analyzer

Power: 9 body-mounted gallium arsenide (GaAs) solar panels; nickel-cadmium (NiCd) battery backup

Propulsion: STAR-30 Solid Rocket Motor; 16-thruster hydrazine system

Protection: Layered dust shield of Nextel and Kevlar fabric

MISSION PROFILE

Launch Vehicle: Boeing Delta II Med-Lite (7425)

Launch Date/Time/Site: July 1, 2002, 2:56 a.m. (EDT), Cape Canaveral Air Force Station, Fla.

Launch Window: July 1–25, 2002 (6-second daily launch opportunities)

Spacecraft Separation: 63 minutes, 30 seconds after launch

First Acquisition of Signal: 85 minutes after launch (Goldstone DSN station, Calif.)

Injection into Sun-Orbiting Earth-Return Trajectory: Aug. 15, 2002

Comet Encounters: Nov. 12, 2003 (2P/Encke); June 19, 2006 (73P/Schwassmann-Wachmann 3)

Earth Swingby Maneuvers: Aug. 2003, Aug. 2004, Feb. 2005, Feb. 2006

Cost: $159 million

CONTOUR MANAGEMENT

Principal Investigator: Dr. Joseph Veverka, Cornell University, Ithaca, N.Y.

Project Management, Spacecraft Development and Mission Operations: The Johns HopkinsUniversity Applied Physics Laboratory, Laurel, Md.

Navigation and Deep Space Network (DSN) Support: NASA Jet Propulsion Laboratory, Pasadena,Calif.

Science Team: 18 co-investigators from universities, industry and government agencies in the U.S. andEurope

CONTOUR Web Site: www.contour2002.org

http://www.ksc.nasa.gov/

http://www.astro.cornell.edu/index.shtml







http://www.ksc.nasa.gov/




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MISSION OVERVIEW

The Comet Nucleus Tour (CONTOUR) is the first mission to study comet diversity by looking at theheart of a comet, its nucleus. CONTOUR’s four-year plan takes it past two short-period comets – 2P/Encke and 73P/Schwassmann-Wachmann 3 – though the mission is flexible enough to include anencounter with a “new” and scientifically valuable comet should one approach the inner solar systemduring CONTOUR’s travels.

CONTOUR will zip to within 100 kilometers (62 miles) of each nucleus, closer than anyspacecraft has ever come to a comet. At each encounter, CONTOUR’s four scientific instruments willtake images and spectral maps of the nucleus and analyze the surrounding gas and dust, providing themost detailed data yet on these mysterious, dynamic and ancient keepers of the solar system’s originalmaterials.

CONTOUR LAUNCH

CONTOUR will lift off from

Launch Complex 17-A atCape Canaveral Air ForceStation, Fla., on a three-stageBoeing Delta II (7425)expendable launch vehicle.The 25-day launch windowopens July 1, 2002, and dailylaunch opportunities last 6seconds. Scheduled takeoff time on July 1 is 2:56:14 a.m.(EDT).

At 511,730 pounds and 125feet tall (232,120 kilogramsand 38 meters), the Delta IIwill provide more than600,000 pounds (2.64 millionnewtons) of thrust at liftoff.

CONTOUR-Delta II launch configuration



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LaunchBoostPhase

Fairingjettison

Time=4minutes,42se

conds

Second-stageignitio

n

Time=4minutes,3

7.5seconds

Mainenginecutoff

Time=4minutes,24seco

nds

Solidrocketjettison(4)

Time=68seconds

Solidrocketimp

act

Second-stageengine

cutoff(#1)

Time=11minutes,

36seconds

Solidrocketburnout(4)

Time=63.1seconds

Liftoff



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LaunchInjectionPhase

Third-stageignition

Time=60minutes,6seconds

Second-stagecutoff(#2)


Spacecraftseparation


Third-stageburnout


Second-stagerestart

Time=58minutes,30se

conds

Thirdstag

eseparated

from

seco

ndstage


EARTH



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INDIRECT LAUNCH MODE

Phasing Orbits and

the Injection

Maneuver

CONTOUR is the firstmission to use the IndirectLaunch Mode, a cleverplan to put a spacecraftinto an elliptical Earthorbit for several weeksbefore propelling it towardits destination. Thismethod affords use of asmaller launch vehicle anda longer launch windowand provides a valuable

chance to monitor thespacecraft while it’s closeto home.

After launch CONTOURwill stay in a highly elliptical Earth orbit, from as low as 200 kilometers (124 miles) out to nearly 115,000kilometers (71,300 miles), until Aug. 15, 2002, when it will be in just the right position for the maneuverinjecting it into a Sun-orbiting, Earth-return trajectory. Performed with the STAR-30 solid rocket motor

– the motor’s only use – the 50-second maneuver will send CONTOUR speeding from Earth at nearly13 kilometers per second, more than 28,000 miles an hour. CONTOUR will be about 225 kilometersabove the Indian Ocean when the maneuver begins at 4:46 a.m. EDT.

EARTH SWINGBYS

Throughout its mission, CONTOUR loops around the Sun and back to Earth for several gravity “swings”toward the target comets. These maneuvers refine (or even change) CONTOUR’s orbit and make itpossible for CONTOUR to reach more than one comet without a large amount of fuel. During the firstEarth swingby, in August 2003, the team will also calibrate the spacecraft’s instruments by photographingthe moon and “tracking” the Earth. The mission includes four Earth swingby maneuvers.

Each orbit takes 42 hours; CONTOUR will make 26 trips around Earth before

the injection maneuver.

Gravity Swings: Closest Approach to Earth (Approx)

Date Kilometers Miles Earth Radii

Aug. 15, 2003 58,000 35,960 9.1

Aug. 14, 2004 40,180 24,600 6.3

Feb. 10, 2005 218,770 133,980 34.3

Feb. 10, 2006 30,000 18,600 4.7

For reference: The average distance between the moon and Earth is about384,500 kilometers, nearly 238,900 miles or 60 Earth radii (R

E).



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HIBERNATION

CONTOUR will cruise between comet encounters and Earth swingbys in a spin-stabilized “hibernation”mode, designed to help the mission reduce spacecraft operations and Deep Space Network trackingcosts. CONTOUR will hibernate for nearly 65 percent of its journey.

During four separate cruise periods – ranging from 120 days to 300 days – mission operators will turnoff CONTOUR’s instruments and most subsystems; only the command receivers, thermostaticallycontrolled heaters and critical core components stay on. The command systems automatically monitorspacecraft status and correct potential faults. The mission operations team stands down while thescience, mission design and navigation teams conduct low-level planning activities.

Ground controllers wake the spacecraft by sending “active spin mode” commands 35 days before eachEarth swingby. This gives them enough time to track the spacecraft, calibrate the instruments and preparefor the swingby maneuver.

COMET ENCOUNTERS

CONTOUR gets its first peek at the target comet several days before each encounter. The nucleus is stillthousands of kilometers away – a mere speck against a background of stars – when the CONTOURForward Imager begins taking pictures the navigation team will use to refine the spacecraft’s path towardthe comet. CONTOUR will transmit pictures and other encounter data just hours after closest approach.

TIMELINE: A Close Encounter with a Comet

60 to 10 days before the encounter:

The mission team determines the spacecraft’s orbit and checks out its systems and instruments.

10 days to 12 hours before: CONTOUR takes pictures and makes spectral observations of the coma.Optical navigation images – used to determine the craft’s and comet’s positions – are taken daily from upto 5 days before, then twice a day thereafter.

12 hours before to 12 hours after: CONTOUR is in full encounter mode; all instruments are turnedon and fill the spacecraft’s data recorders.

12 hours to 15 days after encounter: CONTOUR plays back its data, sending it to the MissionOperations Center through the Deep Space Network. Five days after the encounter CONTOUR changesits trajectory with a short thruster firing, and the mission team determines the spacecraft’s orbit.

• An astronomical unit (AU) is the average distance between Earth and the Sun, about 150 million

kilometers/93 million miles.

• The phase angle is the Sun-comet-CONTOUR angle. Zero degrees would mean the Sun is

directly behind CONTOUR and the comet nucleus is fully lit; an angle of 180 degrees puts the

Sun behind the comet and the nucleus in full shadow (from CONTOUR’s point of view). Low

phase angles are best for viewing larger bodies; fine dust is brightest at high phase angles.

Sun Earth Flyby Phase

Encounter Distance Distance Speed Angle

Date (AU) (AU) (km/sec) (degrees)

Encke, 11/12/03 1.08 0.27 28.2 12

SW3, 6/19/06 0.96 0.32 14.0 101



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CATCHING A “NEW” COMET

CONTOUR’s Earth-return trajectory makes it possible to redirect the spacecraft toward a new comet.For instance, several additional targets are available after the SW3 encounter, including comets6P/d’Arrest and 46P/Wirtanen. More importantly, CONTOUR’s flexibility may allow it a rareopportunity to catch up with a bright, long-period comet that approaches the Sun from the Oort Cloud,

like Hale-Bopp in 1997.

To find suitable candidates as early as possible, CONTOUR supports a worldwide “Comet Watch”program in which amateur and professional astronomers can search for candidate target cometsapproaching from the fringes of the solar system. Information on this program will appear on theCONTOUR Web site during the mission.

MISSION OPERATIONS CENTER

CONTOUR mission operations are conducted from the Mission Operations Center (MOC) at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. Flight controllers and missionanalysts monitor and operate the spacecraft. The operations team works closely with the science team,the mission design team at APL and the navigation team at NASA’s Jet Propulsion Laboratory inPasadena, Calif.

Mission operators and scientists work together to plan, design and test commands for the spacecraft’sinstruments. Working with the mission design and navigation teams, the MOC builds, tests and sends thecommands that fire CONTOUR’s thrusters and set its path back to Earth and toward the comets.

The MOC team sends commands to and receives data from CONTOUR through NASA’s Deep SpaceNetwork (DSN) of antenna stations. Flight controllers monitor CONTOUR’s engineering telemetry toverify spacecraft performance, while MOC computers forward scientific data to the Science Data Center.

SCIENCE DATA CENTER

CONTOUR’s Science Data Center (SDC), located at Cornell University, Ithaca, N.Y., collects, verifies,distributes and stores CONTOUR’s scientific data.

The SDC sends encounter data to science team institutions for processing and validation. GoddardSpace Flight Center in Greenbelt, Md., processes data from the Neutral Gas and Ion Mass Spectrometer(NGIMS); APL and Cornell process data from the CONTOUR Remote Imager/Spectrograph andCONTOUR Forward Imager (CRISP and CFI); and Max Planck Institute in Garching, Germany, processesComet Impact Dust Analyzer (CIDA) data. Processed data then moves to the entire science team forfurther analysis.

The SDC also archives CONTOUR data with NASA’s Planetary Data System and stores engineeringdata for spacecraft troubleshooting and planning activities.



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MISSION TIMELINE

July 1-25, 2002 CONTOUR launches from Cape Canaveral on a Boeing Delta II rocket

Aug. 15, 2002 Injection maneuver into a heliocentric Earth-return trajectory

Aug. 15, 2003 Earth swingby and instrument calibration

Nov. 12, 2003 Encounter with comet Encke

Aug. 14, 2004 Earth swingby

Feb. 10, 2005 Earth swingby

Feb. 10, 2006 Earth swingby

June 19, 2006 Encounter with comet Schwassmann-Wachmann 3

Sept. 30, 2006 Baseline mission ends

SW 38-15-02 8-03 11-03 8-04 2-05 2-06 6-06

Encke

Injectionmaneuver



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NASA DISCOVERY PROGRAM

CONTOUR is the sixth mission in NASA’s Discovery Program of lower cost, highly focused spacescience investigations. Created in 1992, the Discovery Program competitively selects proposals fromscientist-led teams, which carefully plan missions that return the highest science value for the price. Theteams implement the entire mission with minimal NASA oversight. Other Discovery missions include:

NEAR (Near Earth Asteroid Rendezvous) marked the Discovery Program’s first launch, in February1996. The NEAR Shoemaker spacecraft became the first to orbit an asteroid when it reached 433 Eros inFebruary 2000; after collecting 10 times the data expected from its yearlong orbit study, NEARShoemaker carried out the first landing on an asteroid in February 2001.

Mars Pathfinder launched December 1996 and landed on Mars July 4, 1997. The mission demonstratedseveral key tools and techniques for future Mars missions – like touching down with airbags to deliver arobotic rover – while captivating the world with detailed pictures from the Red Planet.

Lunar Prospector orbited Earth’s moon for 18 months after launching in January 1998. The mission’sdata enabled scientists to create detailed maps of the gravity, magnetic properties and chemical makeup

of the moon’s entire surface.

Stardust, now headed for an encounter with comet 81P/ Wild 2, launched in February 1999. Thespacecraft will collect dust as it flies past the comet’s nucleus in January 2004, then it will return thesamples to Earth in January 2006.

Genesis, launched in August 2001, is currently collecting samples of solar wind for return to Earth inSeptember 2004. The samples will help identify what the young solar system was like and help scientiststo understand the elements that formed the planets.

On July 4, 2005, Deep Impact will send a copper-topped projectile crashing into comet 9P/Tempel 1,creating a football field-sized crater seven stories deep and revealing never-before-seen materials and

structural details from inside a comet. Deep Impact launches in January 2004.

MESSENGER (Mercury Surface, Space Environment, Geochemistry, and Ranging) launches in March2004 and begins a yearlong orbit of Mercury in April 2009. MESSENGER will provide the first images of the entire planet and gather data on Mercury’s crust, geologic history, atmosphere, magnetosphere, andcore and polar materials.

Dawn launches in May 2006 toward Vesta and Ceres, the two oldest and most massive asteroids in our solarsystem, and will provide key data on asteroid properties by orbiting and observing both minor planets.

Kepler, planned for a fall 2007 launch, will monitor 100,000 stars similar to our Sun for four years, usingtechnology that allows us to search our galaxy for Earth-size (or even smaller) planets for the first time.

The Discovery Program also includes two Missions of Opportunity – projects on larger non-NASAmissions. ASPERA-3 (Analyzer of Space Plasma and Energetic Atoms) will study the interaction betweenthe solar wind and the Martian atmosphere when it travels on the European Space Agency’s MarsExpress spacecraft, due to launch in June 2003. NetLander, set to become the first network of sciencestations on Mars after ESA launches it in 2007, will investigate the composition and structure of Mars’interior, as well as the weather and climate near the Martian surface.

For more information on the Discovery Program, visit http://discovery.nasa.gov.

http://near.jhuapl.edu/


http://mars.jpl.nasa.gov/default.html


http://lunar.arc.nasa.gov/


http://stardust.jpl.nasa.gov/


http://genesismission.jpl.nasa.gov/


http://deepimpact.jpl.nasa.gov/



http://messenger.jhuapl.edu/


http://www-ssc.igpp.ucla.edu/dawn/


http://www.kepler.arc.nasa.gov/


http://www.aspera-3.org/



http://ganymede.ipgp.jussieu.fr/GB/projets/netlander/


















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THE SCIENCE OF CONTOUR

A Closer Look at Comet Diversity

Comets are some of the oldest objects in the solar system, celestial time capsules preserving a record of the chemical and physical processes at work when the planets began forming more than 4.5 billion years

ago. Scientists believe comets may have brought to Earth some of the water in the oceans, some of thegases of our atmosphere, and even the life-generating molecules from which we arose. But we cannotexamine these possibilities until we know more about comets and understand how individual comets arealike or different.

CONTOUR will visit and study at least two comets – assessing their diversity, detailing their properties,and tackling some of the many questions about how comets evolve.

THE “HEART” OF A COMET

The heart of each comet is the nucleus: a jaggedchunk of ice and rock, often only a few kilometers

across. When a comet gets to within severalhundred million kilometers of the Sun the nucleusheats up, its ices begin to evaporate, and thereleased bursts of gases and dust form a large, thinatmosphere called the coma. These conspicuousfuzzy parts of comets can extend thousands of kilometers from the nucleus. Sunlight sweeps thegases and dust back into a tail that can stretchmillions of kilometers.

Comas and tails are big enough to study withEarth-based telescopes, but the nucleus is so tinythat we can study it only by getting close. So far,we’ve gotten close enough to see the nucleus of acomet only twice: the European Space Agency’sGiotto spacecraft took color photos of comet 1P/Halley’s nucleus in 1986, and NASA’s Deep Space 1collected detailed images and data on comet 19P/Borrelly in 2001.

Comets are the most numerous sizeable bodies in the solar system; current estimates place theirnumber at a million million. Most comets remain where they formed – in the vast region of deep spacethat stretches beyond Neptune and Pluto – but some are bumped from their orbits and approach theSun. Jupiter’s gravity can further alter a comet’s path, capturing it into an orbit that never extends far

beyond the giant planet.

CONTOUR’s planned targets – 2P/Encke and 73P/Schwassmann-Wachmann 3 – belong to Jupiter’s “family”of comets. Encke and SW3 are among the short-period comets, meaning they take less than 200 years toorbit the Sun. CONTOUR will fly past each at the peak of its activity, taking images and spectral maps of thenucleus while measuring and analyzing the surrounding gas and dust.

Comets: A Long Way from Home

Current theories hold that comets come fromtwo distinct reservoirs: the Kuiper Belt of icyobjects beyond Pluto, some 30 to 50astronomical units (AU) from the Sun; and theOort Cloud, about 1,000 times farther than theKuiper Belt, on the fringe of our Sun’sgravitational pull.

Telescopic observations indicate differencesbetween the long-period comets coming fromthe Oort Cloud and the smaller number of short-period comets thought to originate in the

Kuiper Belt; the comas of Oort Cloud cometstypically contain more dust than those of short-period comets, for example.



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CONTOUR’s Key Measurements

• Image the nucleus at resolutions of 4 meters per pixel –10 times better than Deep Space 1 and 25 timesbetter than Giotto – to reveal details of morphology and processes that show how comets work;

• Determine nucleus size, shape, rotation, albedo/color heterogeneity and activity through globalimaging (100-500 meters per pixel);

• Map the composition of the nucleus and coma;

• Obtain detailed compositional measurements of gas and dust near the nucleus;

• Assess the level of outgassing through imaging, spectroscopy, and gas and dust measurements.

CONTOUR’S COMETS

CONTOUR’s target comets wereselected because of their diverse

physical characteristics andproximity to Earth at encountertime. The spacecraft visits Enckeand Schwassmann-Wachmann 3when they’re close to the Sun andat their most active. The cometswill also be relatively close to Earth

– less than 50 million kilometers(31 million miles) – and wellsituated in the night sky forastronomers worldwide to makeconcurrent observations from the

ground.

First spotted in 1786, 2P/Encke

has been observed at moreapparitions (approaches to theSun) than any other comet. It hasthe shortest orbital period of anyknown comet, circling the Sunevery 3.2 years. Encke might be themost famous comet after Halley – American astronomer andCONTOUR scientist Fred Whipple devised the “dirty snowball” model of a comet nucleus after studying

Encke more than 50 years ago.

Encke is thought to be about 8 kilometers (5 miles) long, with an average radius of 2.5 kilometers. Enckeis an “old” comet that gives off relatively little gas and dust, but it remains more active than scientistsexpect for a comet that has made thousands of close passes around the Sun.

73P/Schwassmann-Wachmann 3 was discovered in 1930 and considered predictable by mostastronomers – until it passed close to the Sun in the mid-1990s and split into several pieces. Onefragment has already disappeared; the largest of the remaining sections may be no more than 2

Relative paths: the Sun, Earth, Jupiter and CONTOUR’s comets.

2006 Jun 19

Earth

Encke

Jupiter

2003Nov 12

Sun

S c

h w a s s m

a n n– W

a c h m a n n

3



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kilometers across. A relatively young and active comet – especially when compared to Encke – SW3takes about 5.5 years to orbit the Sun. When CONTOUR reaches SW3 in June 2006, mission scientistshope to get a great look at the comet’s fresh, unaltered surfaces and evidence of the material inside thenucleus.

THE “NEW” COMETThe mission team can use any Earth swingby (after the Encke encounter) to send CONTOUR toward a newtarget. This flexibility may allow it to study a newly discovered long-period comet making one of its first passesaround the Sun, as the bright, spectacular comet Hale-Bopp did in 1997.

For more information on CONTOUR’s targets, visit www.contour2002.org/overview4.html.

COMPARABLE DATA

CONTOUR’s data will cover much of the ground addressed by Giotto at Halley and Deep Space 1 atBorrelly, providing key insights into the differences between Halley-like comets and shorter-period comets

such as Encke and SW3. CONTOUR and NASA’s Stardust spacecraft carry the same dust analyzer, offeringa direct comparison of the missions’ data.

Near their encounter times, Encke and SW3 will be close enough to Earth for astronomers worldwide toobserve them from the ground. CONTOUR’s high-resolution, near-nucleus observations can be linked withpictures, spectroscopic and thermal data obtained at broader scales by ground-based and Earth-orbitingtelescopes.

True to any mission selected through the competitive NASA Discovery Program, the planetary sciencecommunity played a key role in approving CONTOUR and its science goals. The team will furtherenhance the involvement of the science community with the early release of all data to NASA’sPlanetary Data System.

http://www.contour2002.org/overview4.html





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Other Comet Missions

Several spacecraft have already visited comets, setting the stage for a range of missions in the next few years.

In 1985, a NASA team (led by current CONTOUR Mission Director Robert Farquhar) redirectedthe International Sun-Earth Explorer (ISEE) 3 through the tail of 21P/Giacobini-Zinner, setting up

the first spacecraft encounter with a comet. The spacecraft was renamed International CometExplorer (ICE) and made a distant pass of Halley’s comet in 1986.

Halley welcomed an international fleet of spacecraft that year, including the European SpaceAgency’s Giotto, Soviet Union’s Vega 1 and Vega 2, and Japan’s Sakigake and Suisei. Giotto’s famouspictures of Halley’s nucleus and other data paced nearly two decades of comet research andspeculation; Giotto also flew within 200 kilometers of comet Grigg-Skjellerup in July 1992, thoughits camera was damaged during the Halley encounter.

In September 2001, NASA’s Deep Space 1 passed 2,171 kilometers (1,349 miles) from cometBorrelly, taking the best photos of a nucleus to date and revealing a complex body with a variety of terrains and surface textures, mountains and faults, and some of the darkest material in the solar

system. Recent data portray Borrelly’s surface as hot and dry, hiding the ice that might lie below alayer of soot-like material.

Next Up

CONTOUR is one of three NASA Discovery missions to comets. Stardust, already collectinginterstellar dust particles, will fly through the coma of Wild 2 in January 2004 and return samples of the comet’s dust to Earth two years later. Deep Impact will encounter comet Tempel 1 on July 4,2005, launch a camera-toting projectile into the nucleus and observe the pristine materials thatresult from the collision.

The European Space Agency also plans a return to the comets. Rosetta, after a 2003 launch, willconduct a 23-month orbit study of comet Wirtanen starting in August 2011.

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THE CONTOUR SPACECRAFT

CONTOUR’s design is simple and compact: the spacecraft has a body-mounted solar array; few hingedand movable parts; and a mission geometry allowing use of fixed and passive antennas. Controllers pointthe scientific instruments and antennas simply by moving the spacecraft. A layered, heavy-fabric shieldprotects CONTOUR from speeding dust and particles during comet encounters.

CONTOUR has two operating modes. The cruising spacecraft spins steadily on its main axis and“hibernates” unattended for months at a time, with most systems turned off. For comet encounters andEarth swingbys CONTOUR is 3-axis stabilized and fully powered, its attitude fixed and its dust shield andinstruments facing their target.

The Johns Hopkins University Applied Physics Laboratory designed and built the spacecraft, withinstrument and component contributions from institutions and companies around the world.CONTOUR inherits much of its design and components from past or operating missions such as NEAR,TIMED, Cassini and Stardust, thus reducing costs and risks.

Science Payload

CONTOUR’s four scientific instruments will take the most detailed pictures ever of a comet nucleus,map the types of rock and ice on the nucleus, and analyze the composition of the surrounding gas and

dust. The payload includes:

• CONTOUR Remote Imager and Spectrograph (CRISP)

• CONTOUR Forward Imager (CFI)

• Neutral Gas and Ion Mass Spectrometer (NGIMS)

• Comet Impact Dust Analyzer (CIDA)



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CONTOUR Remote Imager/Spectrograph

Mass: 26.7 kilograms (59 pounds)

Power: 45 watts (average)

Supplier: The Johns Hopkins University

Applied Physics Laboratory,Laurel, Md.

CRISP combines a narrow-angle optical imager with a near-infrared spectrometer. CRISP offers top pixelscales of about 4 meters – sharp enough to pick up surface details slightly larger than an automobile – and has 10 filters for visible color study of the nucleus. The spectrometer, covering wavelengths of 780 to2,500 nanometers, has a spatial pixel scale about three times that of the imager.

Instead of facing forward, CRISP points out from the side of the spacecraft, so it remains protected by thedust shield. The camera’s tracking mirror keeps the nucleus in the field-of-view and guides thespectrometer slit across the surface, building up an infrared compositional map. It obtains its sharpestimages just seconds before and after closest approach.

CRISP is CONTOUR’s “smartest” instrument. Scientists will load seven different imaging sequences inthe camera’s computer before each encounter; CRISP waits until the comet appears from behind thedust shield, then selects the appropriate sequence for the comet’s location. CRISP’s computer will alsodirect the spacecraft to “roll” if the comet isn’t quite in its optimal field of view, and its mirrorautomatically tracks the nucleus for a full 30 degrees.

CONTOUR Forward Imager



Supplier: The Johns Hopkins UniversityApplied Physics Laboratory

Peeking through an opening in CONTOUR’s dust shield, CFI locates and starts taking pictures of the targetcomet several days before the encounter. The navigation team uses these distant images to guideCONTOUR toward the nucleus, while the science team watches for phenomena in the coma.

As CONTOUR speeds closer to its target, CFI snaps color photos of the nucleus – capturing themovement of gas and dust jets in the inner coma – and images the coma in wavelengths sensitive tomajor species of ionized gas. Instead of pointing directly at the comet and into the stream of speedingdust, CFI’s telescope looks at a mirror mounted on the side of a cube. After the mirror is peppered andpocked by particles, the cube rotates and supplies a “fresh” mirror for the next encounter.










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Neutral Gas and Ion Mass Spectrometer



Supplier: NASA Goddard Space Flight Center,

Greenbelt, Md.

NGIMS measures the abundance of and isotope ratios for many neutral gas and ion species in eachcomet’s coma. Combined with CIDA’s dust measurements, NGIMS data will yield key information on theelemental makeup of the nucleus and allow scientists to study the chemical differences between thecomets.

Tracing its heritage to the Ion and Neutral Mass Spectrometer on the Saturn-bound Cassini spacecraft,NGIMS is a quadrupole mass spectrometer that employs two ion sources, each optimized for a specific setof measurements. Using both sources, NGIMS will rapidly switch between measurements of neutral gas andambient ions in the coma as CONTOUR zips past the nucleus. NGIMS will measure the chemical andisotopic composition of neutral and ion species over a range of 1 to 294 atomic mass units.

Comet Impact Dust Analyzer



Supplier: von Hoerner & Sulger, GmbH,Schwetzingen, Germany

A copy of the Cometary and Interstellar Dust Analyzer instrument on the Stardust spacecraft, CIDAanalyzes elemental and chemical composition of dust and ice grains in the comet’s coma.

The instrument consists of an inlet, target, ion extractor, time-of-flight mass spectrometer and iondetector. Dust particles hit the target (a silver plate) and generate ions, which are detected by a time-of-flight mass spectrometer. (Since heavier ions need more time to move through the instrument thanlighter ones, the flight times of the ions can be used to calculate their mass.) Detectable sizes range from1 to several thousand atomic mass units, encompassing the elements and many compounds, includingheavy organic molecules.

Both CIDA and NGIMS will collect data continuously for several hours on either side of closestapproach to the comet.

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SPACECRAFT SYSTEMS AND COMPONENTS

Dust Shield

Comet dust particles are like speeding bullets to a spacecraft going 60,000 miles an hour, butCONTOUR has its own bulletproof vest: a 25-centimeter (10-inch) thick, layered shield of Nextel, a

dense fabric like that found in firefighters’ coats (among other uses). Much like the shield protecting theInternational Space Station, its separated layers of Nextel shatter incoming dust grains, and a Kevlarbackstop absorbs remaining debris.

Electronics

CONTOUR uses an APL-developed Integrated Electronics Module (IEM), a space- and weight-saving devicethat puts a spacecraft’s core avionics onto small circuit cards in a single box. CONTOUR’s IEM contains 10cards that comprise the command system, data collection and formatting system, data recorder, guidanceand control processor, and X-band receiver and transmitter. CONTOUR also carries a backup IEM.

PowerCONTOUR draws power from a body-mounted, 9-panel gallium arsenide (GaAs) solar array. Maximumpower depends on solar distance and angle; peak power at 1 astronomical unit (AU) is 670 watts. A9 ampere-hour super nickel cadmium (NiCd) battery stores backup power in case the solar panels pointtoo far off the Sun. The spacecraft is designed to operate out to1.3 AU (195 million kilometers/121million miles) from the Sun. (Note: 1 AU is the average distance from Earth to the Sun, about 150 millionkilometers or 93 million miles.)

Propulsion

CONTOUR has a solid rocket motor and a blow-down hydrazine system. In its only use, the STAR-30

solid rocket motor provides the 1,922 meter-per-second change in velocity (“delta-v”) CONTOURneeds to blast out of Earth’s orbit and enter a heliocentric Earth-return trajectory on Aug. 15, 2002. Thehydrazine system, used tomaneuver the spacecraft for theremainder of the mission, includes16 thrusters placed in fourmodules of four thrusters each.

Telecommunications

CONTOUR’s transceiver-based X-band communications system

includes an 18-inch directionalhigh-gain dish antenna, two low-gain antennas and one pancake-beam antenna. The worldwidestations of NASA’s Deep SpaceNetwork provide contact with thespacecraft after launch.



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CONTOUR uses its high-gain antenna to send data and receive commands when 3-axis stabilized; it usesa low-gain antenna when spinning in Earth orbit and between comet encounters and Earth flybys. Ineither mode, the spacecraft can receive commands and send data at the same time.

Command and Data Handling

CONTOUR’s radiation-hardened, high-performance 32-bit Mongoose V processor receives “time tagged”commands from the ground about a week (or sooner) before a scheduled maneuver or operation.Commands are normally uploaded at rates of 500 bits per second (bps), though the system can supportrates of 7.8 and 125 bps.

For data, CONTOUR carries two solid-state recorders (one backup) capable of storing up to 5 gigabyteseach. Data and telemetry can be downlinked at rates ranging from 11 bps to 85 kilobits per second,depending on CONTOUR’s distance from Earth, whether the craft is spinning or 3-axis stabilized, andwhether it’s communicating through the high-gain or low-gain antennas.

Guidance and Control

CONTOUR’s guidance and control system includes an Earth-Sun sensor, an advanced stellar compass(star tracker) and a gyroscope. When CONTOUR is 3-axis stabilized, its Mongoose V flight computerprocesses location and position information from the sensors to carry out specific Sun-, Earth- orcomet-pointing instructions from mission operators. Ephemeris data on the positions of Earth, the Sunand the target comets is uploaded regularly into CONTOUR’s flight computer.

CONTOUR has no internal reaction wheels. Operators fire the hydrazine thrusters to point, spin up,spin down or otherwise move the spacecraft. The processor in CONTOUR’s primary digital camera(CRISP) also “talks” directly to the flight computer during comet encounters, directing the craft to roll (if necessary) to keep the nucleus centered in the camera’s tracking mirror.

Non-coherent Doppler Tracking

Deep space missions traditionally use transponders for both communication and navigation. Atransponder is a “coherent” system in which the downlink frequency is based on the frequency of theuplink signal from Earth. With such a system, navigators can compare the received downlink frequency tothe known transmitted uplink frequency and determine the velocity of the spacecraft (relative to Earth)from the Doppler effect.

The non-coherent Doppler system on CONTOUR, however, uses a transceiver in which the uplink anddownlink frequencies are independent. The spacecraft uses a simpler transmitter/receiver combinationwith an on-board oscillator. The frequency of the uplink signal received from Earth is compared to thedownlink frequency at the spacecraft, and the results are put into the spacecraft’s telemetry. Before

performing orbit determination, navigators on Earth use this telemetered information to convert thedownlinked Doppler record into what it would have been had it come from a coherent transponder.While this technique requires an additional processing step relative to coherent transponding, itsperformance is just as accurate. It also enables simpler, more flexible hardware to be incorporated intohighly integrated electronics modules such as those flown on CONTOUR.



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PROJECT/PROGRAM MANAGEMENT

The Johns Hopkins University Applied Physics Laboratory, Laurel, Md., manages the CONTOUR missionfor NASA’s Office of Space Science, Washington. Joseph Veverka of Cornell University, Ithaca, N.Y., leadsthe mission as CONTOUR principal investigator.

At NASA Headquarters, Edward Weiler is the associate administrator for space science. ColleenHartman is director of solar system exploration, and Jay Bergstralh is associate director of solar systemexploration. Anthony Carro is the CONTOUR program executive and Thomas Morgan is theCONTOUR program scientist. David Jarrett is the Discovery program manager.

Mary Chiu is the CONTOUR project manager at the Applied Physics Laboratory (APL), which alsodesigned, built and will operate the CONTOUR spacecraft. Edward Reynolds is the deputy projectmanager and mission systems engineer, Robert Farquhar is mission director and Mark Holdridge ismission operations manager. Stamatios Krimigis is head of the APL Space Department.

NASA’s Jet Propulsion Laboratory (JPL), Pasadena, Calif., provides navigation and Deep Space Network (DSN) support. Tony Taylor leads the navigation team and Rich Benson is the telecommunications andmission systems manager.

The CONTOUR Science Team includes co-investigators from Cornell; APL; JPL; University of Texas,Austin;The Johns Hopkins University, Baltimore; Space Telescope Science Institute, Baltimore; LockheedMartin, Denver; Max Planck Institute, Garching, Germany; Malin Space Science Systems Inc., San Diego;NASA Goddard Space Flight Center, Greenbelt, Md.; University of Hawaii, Honolulu;National OpticalAstronomy Observatories,Tucson, Ariz.; Harvard University, Cambridge, Mass.; DLR Institute forPlanetary Exploration, Berlin, Germany; and ESA-European Space Research and Technology Center(ESTEC), Noordwijk, Holland.



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On the cover: Surrounded by dust, CONTOUR speeds past the broken nucleus of comet73P/Schwassmann-Wachmann 3 in this artist’s impression by Dan Maas. When CONTOUR

reaches SW3 in June 2006, mission scientists hope to see relatively fresh, pristine surfaces andevidence of materials inside the nucleus, which split into several pieces in the mid-1990s. The

illustration is part of the CONTOUR Movie, viewable online at www.contour2002.org .





Contour Comet Nucleus Tour Launch Press Kit

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Transcript of Contour Comet Nucleus Tour Launch Press Kit