Hubble Space Telescope Details

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National Aeronautics and Space Administration

Taken from:

Hubble 2007: Science Year in Review

Produced by NASA Goddard Space Flight Center and Space

Telescope Science Institute.

The full contents of this book include more Hubble sciencearticles, an overview of the telescope, and more. The com-

plete volume and its component sections are available for

download online at:

www.hubblesite.org/hubble_discoveries/science_year_in_review

About theHubble Space Telescope


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This Hubbleimage o planetary nebula NGC 2440 shows the colorul last hurrah o a star like our Sun. The star ormed a cocoon o mate-

rial by casting o its outer layers o gas. Ultraviolet light rom the remaining core causes the material to glow. The burned-out star, called a

white dwar, appears as a white dot near the center o the cocoon.

ForewordIn his frst address to the Congress in 1825, President John Quincy Adams proposed a national observatorya lighthouse o the

sky, he called it, with provision or the support o an astronomer, to be in constant attendance o observation upon the phenomena

o the heavens; and or the periodical publication o his observations.

In 1946, Lyman Spitzer conceived o a national observatory in the sky, and 44 years later, in April 1990, it became a reality with the

launch o the Hubble Space Telescope. Today, Hubbleis widely regarded as the most successul scientifc acility in all history.

This book epitomizes Hubbles continuing years o glorious accomplishments, presenting a sample o the activities, operations and

observations, and scientifc fndings rom 2007. Here is our observatory. Here are a ew o our talented people. Here is what we

have done!

NASA plans a fnal servicing mission to Hubblein 2008. Two powerul new instruments are to be installed, and repairs made. Ater

the astronauts do their wonderul work, Hubblewill be more capable than at any time since launch. The science community eagerlyanticipates the new opportunities or research oered by a reurbished observatory. While we do not know exactly what new science

stories will appear in uture editions o this book, we are certain that the rontiers o science will continue to be pushed outward by

the orces o human curiosity and cleverness, channeled by the Hubble Space Telescope.

The lighthouse that is Hubblewill inevitably go dark sometime in the next decade. Today, NASA and its international partners are

currently working hard to complete the James Webb Space Telescope, whose inrared sensitivity will enable it to look deeper into

space and arther back in cosmic time than Hubblecan. Meanwhile, the next generation o Adamses and Spitzers are imagining

larger versions o Hubble, which sometime in the uture will again take up space astronomy in the ultraviolet, visual, and near-

inrared wavelength regimes.


4/33Hubble 2007: Science Year in Review

This Hubbleimage shows the small open star cluster Pismis 24 located to the right o the large emission nebula NGC 6357, and ound in

the constellation Scorpius, about 8,000 light-years rom Earth. Intense ultraviolet radiation rom the massive stars in Pismis 24 is sculpting

the clouds o gas in the nebula.



Equipped with his ve senses, man explores the universe

around him and calls the adventure Science.

Edwin Powell Hubble



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Engineers and technicians conduct a t check in early 1986 on one o Hubbles original retractable solar arrays in a clean room o the

Lockheed Missile and Space Company.

Hubbles HistoryHubbles remarkable mission has now spanned 17 years. During that time, it has been at the

nexus o perhaps the most exciting period o discovery in the history o astronomy. At the same

time, Hubblehas oered up some o the most daunting challenges to humans working in space,

and success in meeting those challenges has been among NASAs greatest triumphs.

Since its launch in 1990, Hubblehas been visited our times by astronauts to x, restore, and upgrade its equipment. In

nearly constant use between these servicing missions, Hubblehas generated data or thousands o scientic papers, on

topics ranging rom discoveries o solar systems in ormation, to precise measurements o the age o the universe.

The concept o a large telescope in space is as old as the space program itsel. In a classied study in 1946, Lyman Spitzer

rst articulated the scientic and technical rationale or space astronomy. He continued to be the champion o the dream o a

large telescope in space until it was realized. Supported by colleagues John Bahcall, George Field, and others, Spitzer was a

tireless advocate within the astronomical community, to the public, and to the Federal Government. The outcome was a new

start or the mission, authorized by Congress in 1977.

The technology needed or the Hubble Space Telescope was well advanced when work began. However, other serious

technological and management challenges characterized the tumultuous years o Hubbles design and manuacture. This

turmoil culminated with the tragic loss o Space Shuttle Challengerand its crew in January 1986. Finally, against the

backdrop o unrestrained anticipation by the public and the astronomical community alike, NASA launched Hubbleinto orbit

on Space Shuttle Discovery(STS-31) on April 24, 1990.



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Hubbles rst ew months were disastrous. Instead o returning crisp, point-like images o stars, its images showed stars surrounded

by large, uzzy halos o light. The source o the problem was traced to an error in constructing the equipment used to test Hubbles

mirror during manuacture. Optical tests using this equipment led technicians to grind the mirror to the wrong shape, giving it a

classic case o spherical aberration. The mirror was perectly smooth, but would not ocus light to a single point.

Hubblewas designed to be visited by astronauts. Even beore launch, NASA had begun to build a second-generation camera

to replace the main camera that was launched with the telescope. Optical experts realized they could build corrective optics into

the camera to counteract the faw in the Hubblemirror. NASA accelerated work on the Wide Field Planetary Camera 2 (WFPC2),

and Hubblescientists and engineers designed a mechanical xture called Corrective Optics Space Telecope Axial Replacement

(COSTAR) to deploy corrective optics in the light paths to the other instruments. In December 1993, astronauts returned to Hubble

and undertook an ambitious set o space walks to install the new equipment. The modications worked fawlessly, restoringHubbles

image quality to nearly the original design goals.

In the decade ollowing the rst servicing mission, Hubblehas treated astronomers and the public to the clearest and deepest viewso the universescenes o proound beauty and intellectual challenge. Thousands o astronomers have used Hubbleor boundary-

breaking research in virtually all areas, rom our own Solar System to the arthest depths o the expanding universe. Three additional

servicing missions in 1997, 1999, and 2002 punctuated this era, and a nal mission to upgrade and reurbish Hubbleis planned

or 2008.

The 1997 mission brought tremendous improvements to Hubbles spectroscopic capabilities with the insertion o the Space

Telescope Imaging Spectrograph (STIS). STIS observations not only demonstrated that black holes are ubiquitous in the centers

o galaxies, but also showed that the black hole masses are tightly correlated with the masses o the surrounding ancient stellar

population. The 1997 mission also opened Hubbles view to the near-inrared universe with the Near Inrared Camera and Multi-

Object Spectrometer (NICMOS). The clear views o distant galaxies provided by NICMOS have supplied a wealth o clues to the

complex physics in the early universe, which led to the ormation o the Milky Way.

The Space Shuttle Columbialited o on February 29, 2002 at dawn, lighting up and disappearing into a cloud cover on its way to servicing

Hubbleor the ourth time.



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In this image, Hubbleprovides a detailed look at the tattered remains o a supernova explosion known as Cassiopeia A (Cas A). It is the

youngest known remnant rom a supernova explosion in our Milky Way galaxy. The complex and intricate structure o the stars shattered

ragments are clearly revealed. This image is a composite made rom 18 separate images, taken in December 2004, using Hubbles Ad-

vanced Camera or Surveys (ACS).

The servicing mission in 1999 enhanced many o Hubbles subsystems, including the central computer, a new solid-state

data-recording system to replace the aging magnetic tape drives, and the gyroscopes needed or pointing control. A month

prior to launch, a gyroscope ailure had orced Hubbleinto sae mode, with no ability to observe astronomical targets.

When a premature loss o solid-nitrogen coolant cut short NICMOSs operational lie, NASA engineers used innovative

mechanical rerigeration technology to develop an alternate way o cooling its detectors to their operating temperature o

320 F. This cooling system was installed in 2002, and it brought the ailing instrument back to lie. NICMOS has proved

crucial to observations o very distant supernovas used to measure the acceleration o the universe. The 2002 mission alsointroduced Hubbles most powerul camerathe Advanced Camera or Surveys (ACS)providing a tenold improvement

over WFPC2.

The nal servicing mission in 2008 will install two new instruments, the Cosmic Origins Spectrograph (COS) and Wide

Field Camera 3 (WFC3). COS is the most sensitive ultraviolet spectrograph ever built or Hubble. The instrument will probe

the cosmic webthe large-scale structure o the universewhose orm is determined by the gravity o dark matter andis traced by the spatial distribution o galaxies and intergalactic gas. WFC3 is a new camera that is sensitive across a wide

range o wavelengths (colors), including inrared, visible, and ultraviolet light. It will study planets in our Solar System, the

ormation histories o nearby galaxies, and early and distant galaxies beyond Hubbles current reach.

Attempts will also be made to repair two instruments currently installed in Hubble: the Space Telescope Imaging Spectrograph

(STIS) and the Advanced Camera or Surveys (ACS). STIS was installed in 1997, and stopped working in 2004. When

repaired, the instrument will be used or high-resolution studies in visible and ultraviolet light o both nearby star systems

and distant galaxies, providing inormation about the motions and chemical makeup o stars, planetary atmospheres, and

other galaxies.



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ACS suered a partial ailure in early 2007 ater operating exquisitely or nearly ve years. Astronomers hope that it

can be restored to its ull capability to perorm high-eciency imaging in both the visible and ultraviolet portions o the

electromagnetic spectrum. Astronauts will also install a reurbished Fine Guidance Sensor to replace one degrading unit

o the three already onboard. Two o these sensors are routinely used to enable Hubbles precise pointing, and the third is

available to astronomers or making accurate measurements o stellar positions.

The Hubble Space Telescope, operating at the intersection o the robotic and the human space fight programs, embodies

both the trials and triumphs o the space program. It has survived controversy, delays, and ailures, and has proven to beone o the most powerul and productive scientic tools ever developed.

Lyman Spitzer, Jr. (19141997) was one

o the 20th centurys great scientists. A

renowned astrophysicist, he made major

contributions in the areas o stellar dy-

namics, plasma physics, thermonuclear

usion, and space astronomy. Spitzer,working under a Research And Devel-

opment (RAND) study in 1946, was the

rst person to describe the detailed ad-

vantages and concepts or a large space-

based telescope, and was a driving orce

behind the development o the Hubble

Space Telescope. (Photo credit: Oce o

Communications, Princeton University)

This detailed Hubbleimage reveals a towering mountain o cold hydrogen gas and dust within the large and complex Carina Nebula

(see ront cover). The great pillars are being eroded away by ultraviolet radiation rom hot young stars in the nebula.


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The Hubble Space Telescope

ACS

The Advanced Camera or Surveys suered two separate electronics ailures ater

operating spectacularly on orbit or about ve years, leaving it unctional now

in only one specialized channel. Astronauts are currently practicing repair tech-

niques that could restore the instrument to ull operation in the post-Sevicing

Mission 4 period.

FGS

Hubblehas three Fine Guidance Sensors on board. Two o

them are needed to point and lock the telescope on the target

and the third can be used or stellar position measurements,

also known as astrometry.

STIS

The Space Telescope Imaging Spectrograph (STIS) is currently not

operating, but is a versatile multipurpose instrument taking ull ad-

vantage o modern technology. It combines a camera with a spectro-

graph and covers a wide range o wavelengths rom the near-inrared

region into the ultraviolet. An attempt is planned to repair the instru-

ment on orbit during Servicing Mission 4.

COSTAR

The Corrective Optics Space Telescope Axial Replacement (CO-

STAR) is not really a science instrument: it is the corrective optics

package that replaced the High Speed Photometer (HSP) during

the rst servicing mission. COSTAR was designed to correct the

eects o the primary mirrors aberration.

NICMOS

The Near Inrared Camera and Multi-Object Spectrometer (NIC-

MOS) is an instrument or near-inrared imaging and spectro-

scopic observations o astronomical targets. NICMOS detects

light with wavelengths rom 800 to 2500 nm.

Primary mirror

Hubbles primary mirror is made o a special glass coated with alumi-

num and a special compound that refects ultraviolet light. It is 2.4 m in

diameter and collects the light rom stars and galaxies and refects it to

the secondary mirror.


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Secondary mirror

Like the primary mirror,Hubbles secondary mir-

ror is made o special glass coated with alumi-

num and a special compound to refect ultraviolet

light. It is .33 m in diameter and refects the light

back through a hole in the primary mirror and into

the instruments.

WFPC2

WFPC2 was Hubbles workhorse camera until the installation o ACS. It records excel-

lent quality images through a selection o 48 color lters covering a spectral range rom

ar-ultraviolet to visible and near-inrared wavelengths. WFPC2 has produced most o the

stunning pictures that have been released as public outreach images over the years.

Solar panelsHubbles third set o solar arrays produces enough power to

enable all the science instruments to operate simultaneously,

thereby making Hubble even more ecient. The panels are

rigid and unlike earlier versions, do not vibrate, making it pos-

sible to perorm stable, pinpoint-sharp observations.

Support systems

Essential support systems such as computers, batteries,

gyroscopes, reaction wheels, and electronics are con-

tained in these areas.

Aperture door

Hubbles aperture door can close, i necessary,

to prevent light rom the Sun rom entering

the telescope.

Communication antennaeData stored in Hubbles solid state recorder is converted to

radio waves and then beamed through one o the spacecrats

high gain antennae to a NASA communications satellite

which relays it to the ground. Because they would extend

out o the image above and below the spacecrat, the anten-

nae are shown here pressed against the side o the telescopein their berthed position. This is how they are congured

when Hubbleis serviced by the astronauts in the payload bay

o the Shuttle.


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Astronaut James H. Newman waves to a cabin-bound crewmate while moving about in Space Shuttle Columbias cargo bay during Servicing

Mission SM3B. Periodic servicing missions have kept Hubbleat the oreront o astronomical research.

Observatory Design

About the size and weight o a subway car, Hubbleowes much o its design to the legacy o the

Cold War, being in many respects, a copy o a KH-11 reconnaissance satellite. Hubbleis just one

o roughly a dozen large telescopes o similar design that have been loted into orbitbut Hubble

was designed to look up, not down.

The heart o Hubbleis its 2.4-m mirror. While small by the standards o ground-based observatories, this mirror collects

about 40,000 times as much light as the human eye, and its location above the distorting eects o the Earths atmosphere

allows Hubbleto obtain very sharp images and view wavelengths o light that do not reach the Earths surace.

Hubblehas an optical layout known as a Ritchie-Chrtien Cassegrain design. The incoming light bounces o the primary

mirror, up to a secondary mirror, and back down through a hole in the primary mirror, where it comes to a ocus on a set o

picko mirrors that guides the light to the scientic instruments. A graphite-epoxy truss provides a rigid structure or the

main optics, and a system o bafes painted fat black is mounted within the telescope to suppress stray or scattered light

rom the Sun, Moon, or Earth.

Hubbleis encased in a thin aluminum shell, blanketed by many thin layers o insulation to reduce temperature fuctuations.

The telescope itsel is housed in the narrower top section o the tube. Most o the control electronics sit in the middle o the

telescope, where the tube widens. The middle section also houses Hubbles our 100-pound reaction wheels. Hubblereorients

itsel around the sky by exchanging momentum with these spinning fywheels. Astronauts can easily access the devices in

Hubbles midsection, and a number o these have been replaced or upgraded during servicing missions. At the back end o the

spacecrat, the at shroud houses the scientic instruments, gyroscopes, star trackers, and other components.


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All o the spacecrats interlocking shellsthe light shield,

orward shell, equipment section, and at shroudprovide a

benign thermal and physical environment, cloaked in darkness,

in which sensitive telescope optics and scientic instruments

can operate properly or many years. Excluding the aperture door

and solar arrays, Hubbleis about 43-t long and 14 t in diameter

at its widest point. Altogether, it weighs about 25,000 pounds.

Hubbles electrical power comes rom two 25-t long solar panels,

which are mounted like wings on the side o the observatory and

rotate to point toward the Sun. Six batteries, charged by solar

power when the Sun is overhead, provide power when the Earth

blocks the Sun. Astronauts replaced the solar arrays on two

occasions during servicing missions. The

present arrays are rigid panels o gallium

arsenide cells that were originally designed or

commercial communications satellites. They

are about 30% more ecient in converting

sunlight to electricity than the prior arrays.When new, they generated about 5,700 W

o electrical power. In a single orbit around

Earth, the exterior surace o Hubblevaries in

temperature rom 150 F to +200 F.

A technician examines the electronic boards in the Cosmic Origins

Spectrograph.

The Cosmic Origins Spectrograph, bagged in anti-static

nylon flm to protect it rom contamination, is shown un-dergoing tests at the Goddard Space Flight Center.


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Despite the harsh thermal environment, the interior o Hubble ismaintained within a narrow range o temperaturesin many areas

at a comortable room temperatureby its thermal control system.

Temperature sensors, electric heaters, radiators, insulation inside

the spacecrat and on its outer surace, and paints that have special

thermal properties, all work in concert to minimize the expansion and

contraction that could throw the telescope out o ocus, and to keep

the equipment inside the spacecrat at proper operating temperatures.

In addition to guiding the telescope, the ne guidance sensors are

used to make very precise measurements o the relative positions o

stars, which is essential or estimating distances to nearby stars or

masses o components o binary star systems.

The at shroud has room or ve scientic instruments.

Over the years, NASA and the European Space Agency

(ESA) have manuactured 12 scientic instruments

or Hubble. Each new generation o instruments has

brought enormous improvements to the scientic

capabilities o the observatory through advances in

technology. Many o Hubbles discoveries with these

new instruments would have been impossible to

achieve with the instruments installed at launch.

Wide Field Camera 3 is lowered into its protective enclosure during a t check

prior to launch.

The Wide Field Camera 3 instrument sits at the bottom o the large

Space Environment Simulator at the Goddard Space Flight Center

as technicians prepare it or an extended thermal-vacuum test.


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Reurbished and ready or action, Hubbleis seen here ollowing its release rom the Space Shuttle Columbiaat the conclusion o Servicing Mission

3B in March 2002. Hubbles next and fnal planned servicing mission is scheduled or autumn, 2008.

Operating Hubble

Circling the Earth at an altitude o 360 miles, Hubble Space Telescopemoves in what is known as

low-Earth orbita zone where the outermost traces o the atmosphere reach into the vacuum o

space. At this altitude, Hubblecompletes an orbit every 96 minutes, moving rhythmically rom the

shadow o the Earth into the bright sunlight and then back again. The looming Earth blocks hal

the sky rom its vantage point, and interrupts most observations by blocking the line o sight to the

target. Without a highly optimized observing schedule, the complications o lie in low-Earth orbit

would doom Hubbleto a low observational eciencyespecially because the bus-sized telescope

can only rotate rom target to target about as ast as the minute hand on a watch. Nevertheless,

careul scheduling keeps Hubblegathering light rom stars and galaxies almost 50% o the time

considerably higher than even the most optimistic predictions at launch.

It is the job o Hubblecontrollers at the Space Telescope Science Institute and NASAs Goddard Space Flight Center to seamlessly

blend science operations and spacecrat operations 24 hours a day. Scientists and engineers at the Institute translate the

research plans o astronomers into detailed sequences o commands or the internal electronics, detectors, and mechanisms o

the scientic instruments. The preparations, carried out weeks or months in advance o the observations, also involve selecting

guide stars to stabilize the telescope pointing, and speciying the exact sequence and timing o the observations. Spacecratcontrollers work together to schedule Hubbles communication with the ground, to load commands into the onboard computers,

to congure the distribution o electrical power rom solar arrays and batteries, and to manage the data in the onboard computers.

The fight operations team at Goddard monitors every system on Hubbleto ensure it is working properly. I one is not, ground

controllers can intervene to remedy the problemi the onboard sang system has not already done soautonomously.


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The primary and secondary mirrors o Hubbleorm an im-

age (ocal) plane whose light is shared by the instruments

and fne guidance sensors (FGS). Seen here are the loca-

tions o the instrument felds o view within the ocal plane

as projected onto the sky (i.e., viewed rom behind the at

end o Hubble). The V2 axis o the telescope is the axis o

the solar arrays. The FGS felds o view are used to locate

and track guide stars. The scale indicates the size o the o-

cal plane in seconds o arc.

In January 2007, the Advanced Camera or

Surveys (ACS), the instrument responsible or

many o Hubbles most impressive images o

deep space, stopped working because o an

electrical short. By February, one part o the

instrumentthe solar blind channel (SBC)was returned to operation by reconguring the electrical system. The SBC

uses a photon-counting detector to study objects in ar-ultraviolet light, while blocking out the visible- and near-ultraviolet

light they emit. The wide-eld channel, known or its ecient collection o light and surveys o the universe, and the high-

resolution channel, capable o taking extremely detailed pictures o astronomical objects, could not be restored. A powerul

new camera is planned or the telescope soon, however. The Wide Field Camera 3 (WFC3) is scheduled or installation

during the second hal o 2008 as part o the nal manned Hubbleservicing mission.

Meanwhile, Hubblestill has other signicant science capabilities. The Near Inrared Camera and Multi-Object Spectrometer

(NICMOS), the Wide Field Planetary Camera 2 (WFPC2), and the Fine Guidance Sensors (FGS) are all working. Observations

that had been scheduled or the still-working instruments were moved, when possible, into the time slots let empty by ACSs

breakdown. The Institute reviewed the unexecuted ACS programs to determine which observations might be transerred to

other instruments, most oten WFPC2. Additional, competitively selected backup programs were created via a special Call

or Proposals, and these were also activated. These eorts made it possible to maintain a high observing eciency and an

excellent science program or Hubble.


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Over the past year, Hubble pursued its usual wide range o scientic programs, targeting objects ranging rom nearby

planets, through stars and clusters in the Milky Way, to galaxies billions o light-years away. Some o the most technically

challenging observations in the present cycle were aimed at the largest planets in the Solar System, Jupiter and Saturn.

The International Geophysical Year was held in 1957, and was marked by the launch o the rst Earth-orbiting satellites. Fity

years later, 2007 was designated the International Heliophysical Year, and marked by a series o scientic projects designed

to study the Suns impact on space physics throughout the Solar System. As part o this campaign, more than 40 planetary

scientists banded together, under the leadership o John Clarke (Boston University), to design a program using Hubbletomonitor how solar weather aects conditions on Jupiter and Saturn. The proposed observations would use the ACS/SBC to

monitor auroral activityexpected to be related to the solar windon those two planets. Moreover, the team proposed to

coordinate some o those observations with the arrival o the New Horizonsspacecrat at Jupiter in February 2007, while a

campaign o Saturn imaging would be coordinated with in situobservations o Saturns magnetosphere by Cassiniin May

2007. Finally, the team proposed observations o Jupiters moon, Io, at least once per day during the 26 days or one entire

rotation o the Sun.

Hubbledata is transmitted to Earth through a NASA relay satellite, which

downlinks it to a ground station in White Sands, NM. From there, it

is orwarded to Goddard Space Flight Center or initial processing and

quality checking. Within minutes, it is sent to the Space Telescope Sci-

ence Institute, where it is urther processed, archived, and made available

to the Principal Investigator who successully proposed the observation.

In a process used in the 14 previous cycles, Hubble

proposals were careully reviewed by a peer committee o

other scientists in the Cycle 15 time-allocation process.

With a request or 162 orbits, the Clarke Jupiter program

qualied as a large program (more than 100 orbits), and

was considered by the Time Allocation Committee (TAC),


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made up o the chairs o the 11 review panels, 2 at-large members, and the TAC chair. The

committee reviewed more than 50 large programs, and recommended the Clarke program or

execution on Hubble. Working with scientists at the Institute, the proposal team developed a

Phase II proposal, speciying the exact sequence o color lters, exposure times, epochs, and

positions. A complicating actor in laying out this program was the necessity to avoid the SouthAtlantic Anomaly, a concentration o energetic charged particles that aects a subset o Hubble

orbits each day. The ACS/SBC cannot be operated during such orbits.

An artists rendition o the New Horizonsencounter with the planet Jupiter.


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The center image was taken by Hubblemore than 500 million miles rom Jupiter, while the bottom rame was

taken by the New Horizonsspacecrats Long Range Reconnaissance Imager while just 16 million miles away.

Through their near-simultaneous imaging, the two missions collaboratively support the ongoing investigation o

the Jovian atmosphere, auroras, and magnetosphere.

For most observations, Hubblelocks on distant guide stars in two o its FGSs, to steady itsel

as it takes exposures. Because Jupiter and Saturn move constantly against the background

stars, Hubblehad to continuously reorient itsel to track the planets, changing guide stars, and

sometimes relying on just a single guide star.

Hubble observations are scheduled on a weekly basis. Individual observations are coded as

a series o commands that are uplinked and stored onboard Hubble, instructing the telescope

where to point, acquire guide stars, and initiate exposure sequences with specic instruments.

The rst set o observations, taken in early January 2007, was acquired without problems.

Then, on January 27, 2007, the ACS suered its serious electrical ailure. Observations weredisrupted or almost three weeks while scientists and engineers rom the NASA project and

rom the Institute ensured that reviving the SBC would not result in irreversible damage to other

components o the observatory. With the New Horizons encounter with Jupiter approaching

rapidly, a series o observations was scheduled using Hubbles oldest operating imaging camera,

WFPC2. WFPC2 oers some ultraviolet imaging capabilities, but neither the sensitivity nor


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the spectral resolution o ACS/SBC. Fortunately, ACS/SBC proved to be recoverable, and the Clarke program resumed

in mid-February.

As is standard, the images were temporarily stored in solid-state memory onboard Hubble, and later downlinked via a

NASA communications satellite to a ground terminal in White Sands, New Mexico. From there, the data were transerred

to Goddard Space Flight Center in Greenbelt, Maryland, and nally to the Institute in Baltimore, where the images were

stored in the Hubbledata archive.

At the same time, an automatic e-mail message was sent to the principal investigators, inorming them that their images

were available as ully processed data sets, reduced using the standard calibration pipeline, and as raw images or

customized processing, i desired.

The next batch o scheduled Hubbleobservations waits within the telescopes computers or execution at prescribed

times. The coordinated eorts o many dedicated, detail-oriented people installed them in the queue. Many more people

will work hard to ensure the observations are completed successully, and then to collect, process, archive, analyze, and

publish the results. Hubble, the fagship o NASAs Great Observatories, has a rst-class crew o scientists, engineers,

and operators, who keep her sailing towards the light, on a grand voyage o discovery.

Multiple simulations o each

Servicing Mission 4 fightday are conducted at the

Space Telescope Operations

Control Center in Green-

belt, Maryland. These help

prepare the ground team to

handle nominal operational

scenarios, as well as the un-

expected.


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This rich galaxy cluster, cataloged as Cl 0024+17, is allowing astronomers to probe the distribution o dark matter in space. The blue

streaks near the center are the smeared images o very distant galaxies that are not part o the cluster. The distant galaxies appear dis-

torted because their light is being bent and magnied by the powerul gravity o Cl 0024+17an eect called gravitational lensing.

HubbleNews

Hubbleobservations have produced a regular stream o news about the universe. Shown here are a

ew recent highlights. Details on these topics and many others can be ound on the World Wide Web at

http://hubblesite.org.

Dark Matter Astronomers using Hubble have evidence o a ghostly ring o dark matter that ormed long ago

during a titanic collision between two massive galaxy clusters. While dark matter is by denition invisible, astronomers

have long suspected its existence as the mysterious substance that holds together galaxy clustersbecause such

clusters would fy apart i they relied only on

the gravity rom their visible stars. Hubble

observations o galaxy cluster Cl 0024+17 reveal

how the total gravity o the system has distortedthe light o more distant galaxies behind

the cluster in a process called gravitational

lensing. This led to the creation o a distribution

map o the unseen matter required to produce the

observed distortions. In a composite published

this year, an image o the cluster made by the

Advanced Camera or Surveys was overlaid

by the distribution map o the invisible matter

(colored blue) needed to account or the observed

gravitational lensing data.

November 1, 2007

A. Dyer, Alberta Canada


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2 Million Miles

45

Comets Hubble has probed thebright core o Comet 17P/Holmes, which,

to the delight o sky watchers, mysteriously

brightened by nearly a million old in a

24-hour period beginning Oct. 23, 2007.

Astronomers used Hubbles powerul

resolution to study Comet Holmes core

or clues about how the comet brightened.Although Hubble cannot resolve the

nucleus, astronomers inerred its size by

measuring its brightness, deducing that the

nucleus diameter was approximately 2.1 milesabout the length o New York Citys Central Park. They hope to use the new

Hubbleimages to determine how much o the nucleus was blasted away during the outburst. Two other Hubblesnapshots

spied three spurs o dust emanating rom the nucleus and revealed an outburst o dust oset rom the nucleus.

Exoplanets Hubbles capable instrument suite has allowed astronomers or the frst time to study the layer-cake

structure o the atmosphere o an extra-solar planet. Known as HD 290458b (depicted in the artist illustrations below), the

planet completes an orbit around its host star every 3.5 days and is about the size o Jupiter. Unlike Jupiter, HD 290458b is so

close to its host star that its atmosphere is pued up. Hubblediscovered a dense upper layer o hot hydrogen gas where the

super-hot planets atmosphere is bleeding o into space. Astronomers used Hubbleto analyze the starlight that fltered through

the planets atmosphere as it passed in ront o its star to reveal the atmospheres structure and chemical makeup.

7,000 Miles

9.6

November 4, 2007

HST WFPC2


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Planets Astronomers have woven Hubbleimages o Saturn, its rings, and several o its moons into three movies. Each

movie highlights unique times in the planets 30-year orbit around the Sun. Two o the movies show the motion o several

o Saturns moons when the planets rings were tilted nearly edge-on to Earth and to the Sun. These edge-on alignments o

the rings occur roughly once every 15 years. Another movie presents a clear view o Saturns southern hemisphere when

the planets rings were at maximum tilt toward Earth. Hubblesnapped only about a dozen images during each o these three

events, so astronomers created sotware to extend the photos into the hundreds o images needed or a movie.


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Galaxies The sharpest image

ever taken o the magnicent galaxy

Messier (M) 81 was released at the

American Astronomical Society

Meeting in Honolulu, Hawaii in May o this year. A spiral-shaped system o stars, dust,

and gas clouds, the galaxys arms wind all the way down into the nucleus. Although

the galaxy is located 11.6 million light-years away, Hubbles view is so sharp that it

can resolve individual stars, along with open star clusters, globular star clusters, and

even glowing regions o fuorescent gas. M81 appears to be undergoing a surge o starormation along the spiral armspossibly due to a close encounter it may have had with

its two neighboring galaxies: spiral NGC 3077 and starburst galaxy M82. Astronomers

plan to use the Hubbleimage to study the star ormation history o the galaxy, and how

this history relates to the neutron stars and black holes seen in x-ray observations o

M81 with NASAs Chandra X-ray Observatory.

Galaxy Clusters Hubble, in collaboration with several other ground- and space-based telescopes, has

captured an odd looking spiral galaxy (shown in the upper let-hand corner o the image) apparently being ripped apart

by the gravitational eld and harsh environment o its associated galaxy cluster. The galaxy is plowing through the

cluster at a speed o at least 3.5 million kilometers per hour ater being accelerated by the enormous combined gravity

o the cluster constituents. As it speeds through, it is disrupted by ramming into hot gas that permeates the cluster.

The galaxys gas and stars are also pulled away by the

gravitational tidal orces exerted rom the clusters core.This nding may shed light on the mysterious process

by which gas-rich, spiral-shaped galaxies are thought

to evolve into gas-poor irregular- or elliptical-shaped

ones. The giant bright banana-shaped arc seen to the

right in the photo is a magnied and distorted image o

a distant galaxy that lies behind the clusters core in an

eect called gravitational lensing.


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Celestial Sphere Google, the company that hosts the popularInternet search engine, has produced Sky in Google Earth through a

partnership with the Space Telescope Science Institute. With Sky in

Google Earth, a visitor can travel across the vastness o the night

sky, making tour stops and zooming in on all o the popular Hubble

images. By clicking on the provided HubbleSite logo, additional

inormation on a particular celestial object is passed to the viewer

rom the associated Hubblepress release.


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Nebulas In celebration o the 17th

anniversary o the launch and deploy-

ment o Hubble, a team o astronomers

released one o the largest panoramic

images ever taken with Hubbles cam-

eras. It is a 50-light-year-wide view o

the central region o the Carina Nebula,

where a maelstrom o star birth and death

is taking place. The antasy-like landscape o the nebula is sculpted by the action o outfowing winds and scorching ultraviolet

radiation rom the monster stars that inhabit this inerno. In the process, these stars are shredding the surrounding material thatis the last vestige o the giant cloud rom which the stars were born. The image is a mosaic o the Carina Nebula assembled rom

48 rames taken with Hubbles Advanced Camera or Surveys. The Hubbleimages were taken in the light o neutral hydrogen.

Color inormation was added with data taken at the Cerro Tololo Inter-American Observatory in Chile. Red corresponds to sulur,

green to hydrogen, and blue to oxygen emission.

Quasars These Hubblephotos show shells o stars around a bright quasar known as MC2

1635+119. Quasars are classied by astronomers as a type o bright active galactic nucleus believed

to contain a central supermassive black hole. The shells presence indicates that a titanic clash with

another galaxy occurred in the relatively recent past. The collision is unneling gas into the galaxys

center, where it eeds the black hole. The accretion o material onto the black hole is the source o the

quasars energy. This observation supports the idea thatat least some quasars are born rom interactions between

galaxies.


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Globular Clusters NGC

6397 (shown at let, taken by a ground-

based telescope) is an ancient globular

cluster containing a dense swarm o hundreds o thousands o stars located

approximately 8,500 light-years rom Earth. The recent Hubble image at top

right reveals two categories o white dwarsthe burned-out relics o normal starsscattered among the other stars o the cluster.

One group is less than 800 million years old; the other between 1.4 and 3.5 billion years. Hubbleastronomers distinguished

the younger rom the older white dwars based on their color and brightness. The younger white dwars (surrounded in blue

squares) are hotter and thereore bluer and brighter than the older ones (surrounded in red circles). The astronomers were

surprised to nd young white dwars located ar away rom the clusters core. They had assumed that the youngsters would

reside at the center and migrate over time to the clusters outskirts. The astronomers proposed that the cluster stars that burn

out as white dwars are given a boost by ejecting masslike rockets dothat propels them to the edge o the cluster.

Supernovas Twenty years ago, astronomers witnessed one o the brightest

stellar explosions in more than 400 years. The titanic supernova, called SN

1987A, blazed with the power o 100 million suns or several months ollowing its

discovery on Feb. 23, 1987. Observations o the supernova made over the past 20

years by Hubbleand many other major ground- and space-based telescopes have

signicantly changed astronomers views o how massive stars end their lives. TheHubbleimage on the right, rom December 2006, shows the supernovas triple-ring

system, including bright spots along the inner ring o gas surrounding the exploded

star. The spots are produced as shock waves o material unleashed by the stellar

blast slam into regions along the inner ring, heating them up, and causing them to

glow. The ring, about a light-year across, was probably

shed by the star about 20,000 years beore it exploded.

The images below show how SN 1987A has changed itsappearance over time.

Hubble Space Telescope Details

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