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Updated February 14, 2001

STS-109 STS-109

Rejuvenating the Rejuvenating the 

World’s Greatest Observatory s Greatest Observatory
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Table of Contents 

Mission Overview ..................................................................................................... 1 

Mission Objectives .................................................................................................. 9 

Introduction ............................................................................................................ 10 

Who Was Edwin P. Hubble? .................................................................................. 14 

Hubble Space Telescope: A Great Observatory Continues Its Quest ............... 15 

Hubble Space Telescope Servicing Mission 3B: Cost to Taxpayers ................. 21 

Future of Hubble: Servicing Mission 4 and Beyond ........................................... 23 

Crewmembers ......................................................................................................... 24 

Flight Day Summary Timeline ............................................................................... 28 

Payloads 

Advanced Camera for Surveys ................................................................................ 29 

Power Control Unit ................................................................................................... 32 

NICMOS Cryocooler ................................................................................................ 34 

Solar Arrays ............................................................................................................. 36 

Reaction Wheel Assembly ....................................................................................... 39 

Rendezvous 

Hubble Space Telescope Rendezvous, Capture, Berthing and Deploy ................... 40 

Spacewalk 

STS-109 Extravehicular Activity ............................................................................... 43 

EVA Timeline Overview ........................................................................................... 53 
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Experiments: DTOs and DSOs 

DTO 700-14 ............................................................................................................. 54 

DTO 805 .................................................................................................................. 54 

DSO 490 .................................................................................................................. 55 

DSO 493 .................................................................................................................. 55 

DSO 496 .................................................................................................................. 55 

DSO 498 .................................................................................................................. 56 

DSO 500 .................................................................................................................. 56 

DSO 503S ................................................................................................................ 56 

DSO 634 .................................................................................................................. 57 

DSO 635 .................................................................................................................. 57 

DSO 802 .................................................................................................................. 57 

Appendix 

Shuttle Reference Data 

Shuttle Abort History ................................................................................................ 58 

Shuttle Abort Modes ................................................................................................ 60 

Shuttle Rendezvous Maneuvers .............................................................................. 64 

Shuttle Solid Rocket Boosters .................................................................................. 65 

Shuttle Super-lightweight Tank ................................................................................ 72 

Acronyms and Abbreviations ............................................................................... 73 

Media Assistance ................................................................................................... 75 

Media Contacts ...................................................................................................... 77 
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Mission Overview

The STS-109 mission of Columbia to service the Hubble Space Telescope is scheduled for 

launch no earlier than 6:48 a.m. EST on Thursday, Feb. 28, 2002, from Launch Pad 39-A 

at the Kennedy Space Center, FL. The mission is commanded by Scott Altman, a 

commander in the U.S. Navy, with Duane Carey, a lieutenant colonel in the U.S. Air Force, 

serving as Pilot. Dr. John Grunsfeld will be Mission Specialist 1 and Payload Commander 

and Nancy Currie, a lieutenant colonel in the U.S. Army, is the Flight Engineer and Mission 

Specialist 2. Dr. Rick Linnehan is Mission Specialist 3, Dr. Jim Newman will serve as 

Mission Specialist 4 and Dr. Mike Massimino will be Mission Specialist 5. 

Altman and Linnehan are making their third flights into space. Grunsfeld, Currie and 

Newman are embarking on their fourth flights, while Carey and Massimino are first-time 

fliers. Currie and Newman flew together on the STS-88 mission in 1998, the first 

International Space Station assembly flight, while Grunsfeld’s last flight in 1999 occurred on 

the last Hubble servicing mission, STS-103. 

Grunsfeld and Newman are spacewalking veterans, while Linnehan and Massimino will be 

conducting spacewalks for the first time. 

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Hubble is serviced by Astronauts Story Musgrave and Jeff Hoffman on STS-61. 

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On STS-109, the Hubble Space Telescope will be serviced for the fourth time since it was 

launched, as Grunsfeld and Linnehan team up to conduct three spacewalks and Newman 

and Massimino are paired for two spacewalks to install new, more durable solar arrays, a 

large gyroscopic assembly to help point the telescope properly, a new telescope power 

control unit and a cooling system to restore the use of a key infrared camera and 

spectrometer instrument which has been dormant since 1999. 

The Advanced Camera for Surveys has the potential to be 10 times more powerful 

in its view of the Universe than the current wide field imager, WFPC 2. 

In addition, almost 12 years after Hubble was launched, the telescope’s view of the 

Universe will be dramatically improved with the addition of the newest scientific instrument - 

the Advanced Camera for Surveys (ACS). With up to four times the speed of previous 

instruments, this device will be able to survey a field of the cosmos twice as large as before 

with ten times the resolution. The new instrument’s potential dwarfs the capability of the 

existing and complementary Wide Field Planetary Camera, which provided the world’s 

astronomers with breathtaking views of the Eagle Nebula and the Hubble Deep Field in 

recent years. The ACS will replace the Faint Object Camera, the last of Hubble’s original 

instruments and the last to require the corrective optics that were installed in Hubble during 

the first servicing mission in 1993. All of the current generation instruments have their own 

internal corrective mirrors. 

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The new solar arrays, which are the third set of power-generating wings for Hubble in its 

history, will generate 20 percent more power at two-thirds the size of the current arrays, 

with a new rigidity and durability that will provide the telescope with enough power for the 

rest of its operational lifetime. Rather than rolling up, the arrays each fold in two sections, 

providing greater reliability than its predecessors. 

Reaction Wheel Assembly (RWA) 

One of four Reaction Wheel Assemblies will be replaced during the flight. This mechanism 

helps to maneuver the telescope into the proper orientation for scientific observations. 

Although the assembly has not failed, it is exhibiting erratic behavior. Only three of the four 

assemblies are required for science, but a new assembly will be installed to insure Hubble’s 

capability for new discoveries in the years to come. 

The new Power Control Unit is the heart of electrical production for Hubble’s systems. This 

unit will collect energy from the new solar arrays and distribute that power to all key Hubble 

components. The original unit has been operating since Hubble’s launch in 1990. With 

Hubble’s mission of discovery now extended to 2010, the new power unit will enable 

Hubble to remain healthier and more productive. Its replacement will be the most complex 

task of the mission, requiring the delicate disconnection and reconnection of 36 small and 

closely spaced electrical connectors by the spacewalking astronauts. For the first time in 

history, all of Hubble’s systems will be completely shut down to accommodate the 

spacewalking upgrade effort, which should take seven hours or more to complete. 

The spacewalks and specific tasks to upgrade Hubble’s instruments are regarded as more 

intricate and challenging than astronauts have encountered in previous servicing missions. 

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Nancy Currie uses the virtual reality lab at the Johnson Space Center to train for 

some of her duties aboard Columbia. 

One of NASA’s Great Observatories, Hubble will be retrieved by Currie using the shuttle’s 

robot arm on the third day of the flight, setting the stage for five consecutive days of 

spacewalks. HST will be berthed on a special work platform at the rear of Columbia’s cargo 

bay, which can swivel and tilt to present various work sites to the spacewalking astronauts. 

Within hours after it is retrieved and berthed, HST’s solar arrays will be rolled up and 

retracted, clearing the way for their replacement on the first two spacewalks of the flight. 

The starboard solar array and its accompanying electronics systems will be replaced on the 

first spacewalk on the fourth day of the mission by Grunsfeld and Linnehan, with the port 

array and its electronics to be replaced the following day by Newman and Massimino. 

During that second spacewalk, the new Reaction Wheel Assembly will also be installed in 

Hubble. 

After each of the arrays is changed out, ground controllers at the Goddard Space Flight 

Center responsible for the telescope’s health and operation will conduct a thorough 

checkout to ensure that the new “wings” are functioning properly. 

During the third and longest spacewalk on the sixth day of the flight, the most intricate task 

of the mission will be attempted. HST controllers will send commands to shut down all of 

Hubble’s systems for the first time to enable Grunsfeld and Linnehan to replace the 

telescope’s Power Control Unit. The component was not originally intended to be replaced. 

But managers elected to change out the 160-pound instrument to accommodate HST 

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operations for the duration of the lifetime of the telescope and to help regulate and properly 

distribute the additional power generated by Hubble’s new solar arrays. Grunsfeld and 

Linnehan will be working primarily by feel as they disconnect and reconnect the control 

unit’s various electrical connectors. Columbia will be maneuvered into the proper 

orientation for the duration of the planned seven-hour spacewalk to maintain the correct 

temperature for the telescope while its thermal systems are shut down. 

The fourth spacewalk by Newman and Massimino on the seventh day of the mission is 

designed to install the new ACS and its associated electronics components. The final 

spacewalk by Grunsfeld and Linnehan on the flight’s eighth day will install a high-tech 

cooling device to regain the use of the Near Infrared Camera and Multi-Object 

Spectrometer, which has been inoperable since early 1999 when nitrogen ice was depleted 

because of a tiny heat leak from a thermos-like instrument designed to keep its infrared 

detectors at a super-cold temperature. 

HST is first deployed on shuttle mission STS-31. 

Currie will operate Columbia’s robot arm once again to redeploy Hubble on the ninth day of 

the mission to continue its unprecedented studies of the cosmos. Science observations 

should resume around three weeks after Hubble is deployed, with the ACS expected to 

offer its first glimpse of the Universe around 9-10 weeks after the mission. Hubble’s next 

shuttle service call is planned for no earlier than the summer of 2004. 

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The flight will be the 27th for Columbia and its first mission since undergoing major 

modifications after its last flight in 1999. STS-109 will be the 108th flight in the history of the 

shuttle program. Landing is scheduled at about 3:38 a.m. EST on March 11, 2002, at the 

Kennedy Space Center. 

Crew

Commander: Scott D. Altman

Pilot: Duane G. Carey

Mission Specialist 1: John M. Grunsfeld

Mission Specialist 2: Nancy J. Currie

Mission Specialist 3: Richard M. Linnehan

Mission Specialist 4: James H. Newman

Mission Specialist 5: Michael J. Massimino

Launch

Orbiter: Columbia (OV-102)

Launch Site: Kennedy Space Center Launch Pad 39A

Launch Window: TBA

Altitude: 308 Nautical Miles

Inclination: 28.5 Degrees

Duration: 10 Days 20 Hrs. 50 Min.

Vehicle Data

Shuttle Liftoff Weight: 4515376 lbs.

Orbiter/Payload Liftoff 

Weight:

257913 lbs.

Orbiter/Payload Landing 

Weight:

221703 lbs.

Software Version: OI-28

Space Shuttle Main Engines: (1 MB pdf)

SSME 1: 2056 SSME 2: 2053 SSME 3: 2047

External Tank: ET-112A ( Super Light Weight Tank) 

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SRB Set: BI111PF

Shuttle Aborts

Abort Landing Sites

 RTLS: Kennedy Space Center Shuttle Landing Facility 

 TAL: Ben Guerir 

 AOA: Edwards Air Force Base, California

Landing

Landing Date: 03/11/02

Landing Time: 3:38 AM (eastern time)

Primary Landing Site: Kennedy Space Center Shuttle Landing 

Facility

 

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STS-109 Mission Objectives 

The Hubble Space Telescope Servicing Mission 3B mission objectives are to complete the 

following tasks: 

• Reaction Wheel Assembly 1 replacement. 

• Replacement of HST’s current solar arrays with new, more durable and more 

capable arrays. 

• The replacement of the HST’s Power Control Unit. 

• The installation of the new scientific instrument, the Advanced Camera for Surveys. 

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Introduction 

The Hubble Space Telescope (HST)—named for the distinguished American astronomer 

Edwin P. Hubble—is an Earth-orbiting observatory which was designed to revolutionize 

astronomy and astrophysics by providing answers to many of the outstanding questions 

which had vexed scientists for decades. In this it has succeeded to a degree that has not 

only thrilled astronomers and energized the international astronomical community, but has 

also served as a source of pride and inspiration to the nation. In addition, HST has paved 

the way for unexpected new findings about our Universe, and these in turn have prompted 

new questions. Such is the cycle of scientific inquiry. 

HST was placed in a 320 nautical mile circular orbit by the space shuttle in April 1990. The 

orbit is inclined at 28.5 degrees with respect to Earth’s equator, and the time for a full 

revolution is 95 minutes. HST’s position lies above the obscuring, absorbing Earth 

atmosphere, which to a greater or lesser extent plagues most observational programs 

carried out with ground-based telescopes. Although its 2.4-meter diameter mirror is only 

moderate in size, HST’s superb optics and the lack of atmospheric distortion produce 

images which are close to the best possible allowed by the laws of physics for a telescope 

of its size. This “diffraction limited” image quality, when combined with complete access to 

the Ultraviolet—Visible—Infrared portions of the electromagnetic spectrum and the very 

dark on-orbit sky “background,” allows HST to perform at its extraordinary level. The 

triumph of these advantages over a moderate size mirror is illustrated by the fact that HST 

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not only detects but also reveals morphological structure in extremely distant galaxies seen 

when the Universe was a small fraction of its current age. Ground-based telescopes, in 

spite of their often vastly superior size and numerous important contributions to astronomy, 

are unable to achieve comparable depth with resolution. 

An artist’s concept of the Space Telescope 

From the beginning, NASA and the designers of HST had in mind a broadly capable 

observatory which could attack a wide variety of astronomical questions using a suite of 

diverse scientific instruments (SIs) collectively operating over a wide wavelength (color) 

range from the ultraviolet (UV) to the Infrared (IR). The most obvious breakdown of 

instruments is by basic type, e.g., imaging camera or spectrograph. Less familiar to the 

public than imagers, spectrographs decompose the light from astronomical targets into its 

separate wavelengths or colors, resulting in knowledge about an object’s composition, 

temperature, pressure and motion. Imaging cameras are important for determining the 

morphology, structure, brightness and color of celestial objects. 

HST has slots, or “bays,” for five different SIs, and a key component of the 20-year program 

is that from time to time the instruments are replaced by newer, much more technologically 

capable SIs. The space shuttle and its crew of EVA astronauts are the means by which 

these new SIs—as well as replacement engineering hardware such as gyroscopes and 

solar arrays—are installed in HST. The Hubble program is now 12 years old, and on-orbit 

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servicing of the telescope has obviously been a key and irreplaceable element in the 

telescope’s success. Highlights: 

• The First Servicing Mission (SM1) in 1993 restored HST’s optical acuity to the 

original expected levels and replaced its solar arrays 

• With the installation of NICMOS and STIS during SM2 in 1997, HST observed the 

infrared sky for the first time and began taking detailed 2-dimensional spectra of 

black hole environments in the centers of galaxies 

• SM3A in 1999 brought HST back on-line scientifically with the installation of a fresh 

set of gyroscopes, and upgraded its capabilities with a new computer 

SM3B in February 2002 will be a very full, diverse mission, as both major scientific 

improvements and engineering maintenance and upgrades will be carried out. The next 

section of this document will discuss the scientific aspects of SM3B in more detail. 

SM3B and SM4: Extending HST’s Scientific Legacy 

When the astronauts leave Hubble behind in orbit after the final service call, SM4 in 2004, 

they will be leaving the observatory at the peak of its capabilities. Three new scientific 

instruments inserted in 2002 and 2004, the Advanced Camera for Surveys (ACS, inserted 

during SM3B), the Cosmic Origins Spectrograph (COS, SM4) and the Wide Field Camera 3 

(WFC3, SM4), will be 10 to 20 times more powerful than their predecessor Hubble 

instruments. The insertion of the NICMOS Cooling System (NCS) in 2002 will restore 

Hubble’s capability to take images in near-infrared light, and this capability will be 

dramatically strengthened with the WFC3 near-IR channel in 2004. 

ACS has the potential to be 10 times more powerful in its view of the Universe than the 

current wide-field imager, WFPC2. It achieves this 10X performance as a result of a 

detector sensitivity which is five times greater than that of WFPC2 in the very important red 

region of the spectrum, and a field of view which has twice the area of WFPC2. An 

additional bonus is that ACS has twice the angular resolution that WFPC2 possesses over 

wide fields. Thus, the advantages are that: ACS will be able to detect faint objects much 

more quickly than WFPC2 could; will cover twice the sky area per exposure, which brings 

an important efficiency in mapping regions of the sky; will reveal morphological structure in 

smaller objects; and will detect distant galaxies and other dim objects significantly fainter 

than WFPC2 could in exposures of the same length. ACS will bring these advantages to 

bear in an extremely broad range of observing programs carried out by the astronomers 

who were granted telescope time in the last round of competitive proposal review. One 

thing seems certain: with ACS’s installation we will have the capability of looking deeper 

into the Universe with greater clarity than we ever have before. Astronomers in large 

numbers have been looking forward to ACS’s arrival for years, and that time is now at 

hand. 

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The NCS is a mechanical refrigeration system, or “cryocooler,” which will restore HST’s IR 

instrument, NICMOS, to full operational status. NICMOS entered a period of “hibernation” 

in January 1999, when its solid nitrogen ice coolant ran out. The instrument’s detectors, for 

a variety of reasons, need to be kept very cold to achieve adequate scientific importance. 

The two-year period during which NICMOS did operate showed the great advantages the 

infrared brings to HST science. First, many objects in the Universe are cool and radiate 

much of their light in the IR. Second, infrared light is much less strongly scattered by dust 

than is visible and ultraviolet light, which means that the IR is the color of choice when 

observing dusty environments such as the birthplaces of stars. Last, because the Universe 

is expanding, the UV and visible light from very distant galaxies is “redshifted” into the IR. If 

an astronomer wants a complete description of such a galaxy, it is therefore important to 

observe it over the entire UV-Visible-IR range of colors. In addition to the IR science, which 

the NCS will hopefully re-enable, the cryocooler will serve as a trailblazer for the 

applicability and function of mechanical refrigeration systems in space. 

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Who Was Edwin P. Hubble? 

Edwin P. Hubble 

One of the great pioneers of modern astronomy, the American astronomer Edwin Powell 

Hubble (1889-1953) started out by getting a law degree and serving In World War I. 

However, after practicing law for one year, he decided to “chuck law for astronomy and I 

knew that even if I were second rate or third rate, it was astronomy that mattered.” 

He completed a doctoral dissertation on the Photographic Investigation of Faint Nebulae at 

the University of Chicago and then continued his work at Mount Wilson Observatory, 

studying the faint patches of luminous “fog” or nebulae in the night sky. 

Using the largest telescope of its day, a 2.5-m reflector, he studied Andromeda and a 

number of other nebulae and proved that they were other star systems (galaxies) similar to 

our own Milky Way. 

He devised the classification scheme for galaxies that is still in use today, and obtained 

extensive evidence that the laws of physics outside the Galaxy are the same as on Earth—

in his own words: “verifying the principle of the uniformity of nature.” 

In 1929, Hubble analyzed the speed of recession of a number of galaxies and showed that 

the speed at which a galaxy moves away from us is proportional to its distance (Hubble’s 

Law). This discovery of the expanding Universe marked the birth of the “Big Bang Theory” 

and is one of the greatest triumphs of 20th-Century astronomy. 

None other than Albert Einstein could have predicted Hubble’s remarkable discovery some 

10 years earlier. In 1917, Einstein applied his newly developed General Theory of Relativity 

to the problem of the Universe as a whole. Einstein was very disturbed to discover that his 

theory predicted that the Universe could not be static, but had to either expand or contract. 

Einstein found this prediction so unbelievable that he went back and modified his original 

theory to avoid this problem. Upon learning of Hubble’s discoveries, Einstein later referred 

to this as “the biggest blunder of my life.” 

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Hubble Space Telescope: A Great Observatory Continues Its Quest 

A Promise Fulfilled 

A golden era of space exploration and scientific discovery began April 24, 1990, with the 

launch and deployment of NASA’s Hubble Space Telescope (HST). This first of NASA’s 

“Great Observatories” was carried into space aboard the Space Shuttle Discovery during 

the STS-31 mission, and was deployed on April 25, 1990. 

Gas Pillars in M16 - Eagle Nebula 

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During its nearly 12 years of operation, and especially since the First Servicing Mission 

(SM1) in December 1993 restored its optical performance to expected levels, HST’s 

unprecedented rapid-fire rate of discoveries has invigorated astronomy and instilled in the 

public a sense of wonder and an appreciation for scientific inquiry. HST has proven to be a 

remarkably diverse tool for examining planets, stars, star-forming and probable 

planet-forming regions of the Milky Way, distant supernovae, galaxies and quasars, and the 

hydrogen gas lying between the galaxies. Not since the invention of the telescope 400 

years ago has our vision of the Universe been so revolutionized, and over such a short 

period of time. HST has been responsible for nothing less than a re-writing of the 

textbooks on astronomy and astrophysics. 

The most technologically advanced scientific instruments HST will ever contain have not 

yet been installed in the telescope; these improvements will occur in the final two servicing 

missions, SM3B and SM4 (in 2002 and 2004), and will leave HST at the peak of its 

scientific capabilities for the last eight years of its life. Such technological growth leading to 

vastly increased scientific capability has been occurring since 1993, and is exactly what the 

mission architects envisioned decades ago when the HST program was born. Clearly, 

much of HST’s best science lies yet ahead. 

The Telescope and Its Operations 

The 12-ton HST observatory takes full advantage of its location in Earth orbit. Because the 

light from celestial targets reaches the telescope without traversing the atmosphere, it does 

not suffer from distortion (e.g., twinkling starlight), and the result is extremely sharp and 

detailed images of planets, stars and galaxies, in spite of HST’s rather modest 8-ft (2.4 m) 

diameter primary mirror. A major advantage of observations from space is that the 

important ultraviolet and infrared regions of the electromagnetic spectrum are fully available 

for study, unlike the situation on the ground, where atmospheric absorption in those 

wavelength regions is a problem. Lastly, the night sky is significantly darker on-orbit than 

on the ground, and hence offers better contrast for detecting and studying faint objects 

such as extremely distant galaxies. 

At any given time in its 20-year mission, HST contains up to five scientific instruments (SIs), 

and the collective set offers a broad range of capabilities in imaging and spectroscopy over 

a wide wavelength interval. The SIs all use on-board microprocessors, which issue the 

commands to execute pre-planned/stored observational programs. The heart of each 

instrument is its detector, an electronic device which converts light to electrical signals 

across its active area, and sends the data to HST’s data recorders for later radio 

transmission to orbiting data relay satellites and, ultimately, the ground. One type of 

detector which is well-known due to its presence in camcorders is the Charge Coupled 

Device, or CCD, which in astronomy is most frequently used for visible light imaging and 

spectroscopy. Other features of SIs are filters and gratings, which for imaging and 

spectroscopic applications, respectively, select the wavelength range of the light the 

astronomer wants to detect and analyze. Spectroscopy—less well-known than imaging to 

non-scientists—is the study of an object’s chemical composition, temperature, motion, and 

age by means of dispersing the light into its various colors or wavelengths. 

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Besides the scientific instruments, major elements of HST include: a central computer 

which coordinates the functions and relays the telemetry from the major subsystems 

aboard the telescope; a pair of solar arrays which extend from the sides of the telescope 

and generate the required electrical power for operating the SIs and the subsystems, and 

for charging the telescope’s six batteries; a pair of high-gain antennas for receiving and 

transmitting data from/to relay satellites and ground stations; and a complex pointing 

control system for keeping the telescope extremely precisely and stably pointed at the 

target being observed. The importance of stable pointing can hardly be overemphasized. 

The superb imaging quality of HST requires extraordinary stability in order that jitter and 

image drift not produce significant image degradation during long exposures. A benchmark 

of HST’s optical quality is that it can produce images of the outer planets in our solar 

system that approach the clarity of those from the Voyager flybys. 

A rare and spectacular head-on collision between two galaxies appears in this 

NASA Hubble Space Telescope true-color image of the Cartwheel Galaxy, located 

500 million light-years away in the constellation Sculptor. 

HST operates around the clock, gathering information for teams of scientists who study 

virtually all the constituents of the Universe. Overall responsibility for HST, including the 

program to service and upgrade the telescope, resides with the HST Project at Goddard 

Space Flight Center (GSFC, in Greenbelt, Maryland). HST is controlled and receives 

commands from the Space Telescope Operations Control Center (STOCC), resident at the 

Space Telescope Science Institute (STScI) in Baltimore; STScI’s major function is to plan 

and administer the science program of HST. A second STOCC at GSFC is used for 

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commanding HST during servicing missions. Every day, data obtained by HST streams 

through a series of satellite relays to the GSFC and then by telephone line to the STScI, 

where the raw data are converted into scientifically useable data, calibrated, and archived. 

The information collected daily by Hubble is stored on optical computer disks. The 

constantly growing archive of Hubble data is a unique scientific resource for current and 

future astronomers. 

The observations carried out by HST result from an annual competitive process, conducted 

by the STScI, in which astronomers from around the world propose for observing time on 

the telescope. Recent observing cycles have seen submissions of more than 1,000 

scientific proposals for time on HST. An indication of the importance of HST to astronomers 

is that many more proposals are submitted than can be accommodated. The 

“oversubscription factor” is typically in the range of 4X-6X; the current value is 8X. Clearly, 

the science programs executed by HST represent the cream of the crop of those proposed. 

Servicing HST 

In addition to upgrading the telescope with new, dramatically improved instruments, 

servicing missions are critical for replacing aging and worn-out components, and hence 

keeping the telescope running smoothly. This latter maintenance function is exactly 

analogous to maintenance performed on one’s automobile, for example. Experience has 

shown that HST servicing missions should be carried out approximately every three years. 

Three missions—all extremely successful—have been flown to date: SM1 in December 

1993; SM2 in February 1997; and SM3A in December 1999. Because HST’s gyroscopes 

needed to be changed out earlier than expected, the content of the original SM3 was 

divided up into two pieces—A and B—with SM3B coming in February 2002. 

When the astronauts leave Hubble behind in orbit after the final service call, SM4 in 2004, 

they will be leaving the observatory at the peak of its capabilities. Three new scientific 

instruments inserted in 2002 and 2004, the Advanced Camera for Surveys, the Cosmic 

Origins Spectrograph and the Wide Field Camera 3, will be 10 to 20 times more powerful 

than their predecessor Hubble instruments. The insertion of the NICMOS Cooling System 

in 2002 will restore Hubble’s capability to take images in near-infrared light, and this 

capability will be dramatically strengthened with the Wide Field Camera 3 near-IR channel 

in 2004. The remaining two missions, SM3B and SM4, will complete the process of 

modernizing Hubble’s spacecraft and making it less prone to failures. 

Hubble’s Major Contributions to Astronomy 

There is virtually no area of astronomical research that has not been profoundly affected by 

Hubble observations. Some of the highlights of Hubble’s scientific achievements to date 

include the following: Hubble 

• Took the deepest views ever made of the visible Universe, revealing galaxies dating 

back to within a billion years of the Big Bang. These observations have opened up 

new areas of research into how galaxies form and evolve and what happened in the 

earliest days of the Universe. Astronomers are discovering that proto-galaxies in the 

early Universe were small irregular clumps which grew by colliding and merging, and 

which formed stars at a rapid rate. 

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• Precisely measured the current expansion rate of the Universe, a value sought for 

nearly 70 years since Edwin Hubble first discovered the Universe is expanding 

uniformly in all directions. 

• Made the definitive observations showing that the Universe is destined to expand 

forever, and is even accelerating, apparently driven by “dark energy,” a mysterious 

repulsive form of gravity that is pervasive among the galaxies. 

• Found that the Universe’s most powerful explosions, gamma-ray bursts, happen in 

distant galaxies in regions where massive new stars are rapidly forming. This links 

the gamma-ray bursts to the catastrophic deaths of super-massive stars. 

• Discovered that super-massive black holes dwell in the cores of most galaxies. 

Specifically, black holes are found at the centers of galactic “bulges” – either 

elliptical galaxies or the central bulges possessed by most spiral galaxies. There is a 

very tight relation between the mass of the “bulge” and the mass of its central black 

hole. This implies a direct link between the growth of galaxy “bulges,” the growth of 

their black holes, and quasars, which occur when a massive black hole “swallows” 

more mass. 

• Provided the clearest views ever of the diverse and complex processes at work in 

the birth and the death of stars. For newly forming stars these include the formation 

of accretion disks of gas and dust and the periodic ejection of material, focused into 

narrow jets by magnetic fields around the star. For stars that have exhausted their 

fuel sources at the end of their lives, Hubble has revealed the exquisite diversity of 

forms taken by the material ejected from the stars and how this relates to a star’s 

specific circumstances. Hubble has chronicled the spectacular changes in 

Supernova 1987a as its blast debris plows into material surrounding the star. 

• Showed that the first embryonic steps in planet formation are common around many 

stars in the form of vast disks of gas and dust that should rapidly precipitate planets. 

However, many of these disks rapidly lose the gas (mostly hydrogen) they contain 

as they are bombarded by energy from nearby bright, massive stars in large starforming regions. This suggests gas-giant planets like Jupiter or Saturn may be 

relatively rare in the Galaxy. 

• Observed unique gap and ring structures within vast dusty circumstellar disks which 

are potentially attributed to the gravitational influence of large planets or protoplanets 

existing much farther from the parent star than found in our solar system. 

Interestingly, the analysis of some cometary orbits in the solar system also suggests 

the potential existence of a perturbing planet at a great distance from the sun. 

• Provided stunningly clear views of the northern and southern lights on Jupiter, 

Saturn and Ganymede (a moon of Jupiter), as well as images of the electrical 

interactions between Jupiter and its satellite Io. Hubble provided the first visual 

evidence of major climate changes on the outer planets Uranus and Neptune and 

the first coarse map of the surface of Pluto. 

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Before the launch of Hubble in 1990, people referred to our “conscious expectation of the 

unexpected.” That was a sensible viewpoint, because as it has turned out, 40 percent of 

the highest-impact scientific achievements of Hubble were unanticipated. We cannot today 

anticipate very accurately what scientific problems will be most pressing five or six years 

from now. But we can anticipate that the Hubble Space Telescope will be deeply involved 

in the forefront of that science. 

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Hubble Space Telescope Servicing Mission 3B 

Cost to Taxpayers 

NASA's Hubble Space Telescope is the first observatory designed for routine maintenance, 

upgrade, and refurbishment on orbit. The program is planned as a 20-year mission with 

periodic servicing by shuttle astronauts. Hubble's modular design allows for more than 90 

spacecraft components and all of the scientific instruments to be replaced on orbit. 

Servicing maintains the spacecraft, ensures operation at maximum scientific efficiency and 

allows for incorporation of new technology. 

Hubble was launched on April 24, 1990, with a full complement of six scientific instruments. 

At that time, an inventory of spare HST hardware was available to support future servicing 

missions. Since launch, HST budgets have been sized to develop new instruments, to 

maintain the spare hardware, to sustain hardware expertise, to plan and develop servicing 

activities, and to test and integrate the payloads with the shuttle. 

Due to gyroscope failures and the potential for interruption of the science program should 

another gyroscope fail, a servicing mission was needed as soon as replacement gyroscope 

hardware could be ready. Servicing Mission 3 (scheduled for June 2000) was divided into 

two flights --- Servicing Mission 3A (SM3A), successfully completed in December 1999, and 

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Servicing Mission 3B (SM3B), scheduled for early 2002. Much of the hardware planned for 

Servicing Mission 3 was not ready in time for the first flight, and will therefore be installed 

during SM3B. 

Servicing Mission 3B 

The Advanced Camera for Surveys (ACS) will be added to Hubble’s complement of already 

superb scientific instruments, further enhancing its imaging capability by a factor of 10. The 

Power Control Unit (PCU), which controls and distributes electricity from the solar arrays 

and batteries to other parts of the telescope, will be replaced. Hubble will get a brand new 

look with a new set of rigid solar arrays. Although one-third less solar cell area than the 

flexible first two pairs, they produce 20 percent more power. One of four reaction wheel 

assemblies (RWA), which is part of Hubble’s pointing control system, will be replaced. Spin 

momentum in the reaction wheels moves the telescope into a commanded position and 

maintains it in this stable position. 

Astronauts also will retrofit an existing but dormant instrument called the Near Infrared 

Camera and Multi-Object Spectrometer (NICMOS) with a new, experimental cooling 

system to return it to active duty. By fitting NICMOS with the experimental cryogenic 

system, NASA hopes to re-cool the NICMOS detectors, reviving its infrared vision, and 

extending its life by several years. 

Servicing Mission Costs – HST 

Planned Servicing Mission Hardware & Software 

 Advanced Camera for Surveys 76 

 Solar Array 3 19 

 NICMOS Cryocooler 21 

 Simulators/Testing 31 

 Ops/Software Development 25 

 Total (Millions) 172 

For additional information contact: 

Nancy Neal 

Goddard Space Flight Center 

Office of Public Affairs 

(301) 286-0039 

Internet: http://www.gsfc.nasa.gov

Don Savage 

NASA Headquarters 

Office of Public Affairs 

(202) 358-1600 

Internet: http://www.nasa.gov

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Future of Hubble: Servicing Mission 4 and Beyond 

Plans for SM4 include two Science Instruments, which are currently in development. 

COSTAR will be removed during this servicing mission to make room for the Cosmic 

Origins Spectrograph, and Wide Field Camera 3 will replace the Wide Field and Planetary 

Camera 2. Also, a refurbished Fine Guidance Sensor will be installed leaving Hubble in 

optimum condition. 

Cosmic Origins Spectrograph 

COSTAR will be removed and replaced with the Cosmic Origins Spectrograph (COS). COS 

is a spectrograph specifically designed to observe into the near and mid ultraviolet. The 

ultraviolet region is particularly interesting for observing high-energy activities such as are 

found in new hot stars and Quasi Stellar Objects. It is also a good region for viewing the 

composition and character of the Interstellar Medium. 

Wide Field Camera Three 

Wide Field Camera Three (WFC3) will be the last main imaging camera. WFC3 will replace 

the current workhorse of Hubble, Wide Field and Planetary Camera 2. This upgrade will 

allow Hubble to maintain good imaging capabilities throughout the remainder of its mission. 

Everyone has seen the amazing pictures generated by the Wide Field and Planetary 

Cameras (1 and 2). WFPC2 was installed during the 1993 servicing mission and will be 

more than 10 years old when it is replaced by the WFC3. 

Aft Shroud Cooling System 

This new system is designed to carry heat away from scientific instruments in the Aft 

Shroud area of the Telescope assembly and to allow the instruments to operate better 

at lower temperatures. The cooling system allows multiple instruments to operate 

simultaneously, helping the science team maintain the program's high productivity

Fine Guidance Sensor 

The Fine Guidance Sensors are systematically refurbished and upgraded. In “roundrobin” fashion one FGS per servicing mission is being replaced. It is returned to the 

ground, disassembled and refurbished, and then taken back to Hubble on the next 

servicing mission to become the replacement unit for the next FGS to be serviced. By 

the conclusion of SM4 all three FGS’s will have been brought up to optimum condition in 

this manner. 

Closeout Mission 

NASA will determine the best approach to secure the Telescope, upon the completion 

of Hubble’s 20-year mission. Currently there are several options being considered. 

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Crew Bios 

Crewmembers 

Commander: Scott Altman

Scott D. Altman, 42, a Navy commander, a former test pilot and 

veteran of two spaceflights, will command Columbia’s STS-109 

flight to the Hubble Space Telescope and be responsible for the 

mission’s safety and success. He will fly Columbia through its 

rendezvous and capture of the space telescope on the 108th flight 

of the Space Shuttle Program, and will fly the shuttle during 

Hubble’s release. He will be one of the three robotic arm operators 

on board Columbia. He will have primary responsibility for Earth 

observations, and will share responsibilities for the shuttle’s 

guidance and navigation systems, computer systems and live 

support systems. He will land Columbia at the end of the mission. 

Altman was pilot on STS-90, the 16-day Neurolab mission in April and May of 1998. He 

also was pilot on STS-106 in September 2000, a mission to prepare the International 

Space Station for the arrival of the Expedition One crew. 

Pilot: Duane Carey 

An Air Force lieutenant colonel and like his commander a former 

test pilot, Duane G. “Digger” Carey, 44, holds a master’s in 

aerospace engineering from the University of MinnesotaMinneapolis. He will be responsible for a number of orbiter systems 

during ascent and landing. He will assist his commander in 

rendezvous, capture and later release of the Hubble Space 

Telescope. Other responsibilities include orchestrating the 

photographic and video graphic documentation of the mission. 

Carey also will be one of two medics aboard Columbia. 

Carey, who was selected as an astronaut in 1996, is making his first space flight. 

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Mission Specialist 1: John Grunsfeld

John M. Grunsfeld, 43, is the Payload Commander on STS-109 

and is responsible for the payload operations and execution of the 

flight’s five spacewalks. He holds a Ph.D. degree in physics from 

the University of Chicago, and served on the faculty of the 

California Institute of Technology where he did research in highenergy astrophysics and astronomy. He is making his second visit 

to service the Hubble Space Telescope. He and Richard Linnehan 

will be one of two space-walking teams that will alternate on 

consecutive days to make a total of five spacewalks to repair and 

upgrade the HST. Grunsfeld will make three spacewalks with fellow 

mission specialist Linnehan. They will serve as coordinators on the 

mission’s other two spacewalks. Grunsfeld also will serve as ascent mission specialist and 

have responsibilities for opening and closing Columbia’s payload bay door, computers, and 

EVA tools. 

Grunsfeld, who was selected as an astronaut in 1992, is a veteran of three space flights. 

He first flew on STS-67, the second flight of the Astro observatory, a flight dedicated to 

astronomy research, which operated a suite of Ultra-Violet telescopes, in March 1995. He 

was a mission specialist on STS-81, a 10-day mission to the Russian space station Mir in 

January 1997, which also included a suite of experiments for biological research. On the 

STS-103 mission to service the Hubble Space Telescope, in December 1999, he 

performed two spacewalks. 

Mission Specialist 2: Nancy Currie

Selected as an astronaut in January 1990, Nancy Jane Currie, 43, 

holds a Ph.D. in industrial engineering from the University of 

Houston and is an Army lieutenant colonel. She served as a 

helicopter instructor pilot and is a Master Army Aviator. She 

accumulated over 4,000 flying hours in rotary and fixed-wing 

aircraft. She was robotic arm operator during STS-88, the first 

International Space Station assembly mission, and will be at the 

controls of Columbia’s robotic arm during STS-109 capture and 

redeployment of the Hubble Space Telescope and during the five 

spacewalks to repair and upgrade it. She also will have 

responsibilities as the flight engineer aboard Columbia. 

Currie is a veteran of three space flights, serving as a mission specialist and flight engineer 

on all of them. STS-57 in June of 1993 featured Spacehab microgravity experiments and 

return of the European Retrievable Carrier satellite. STS-70 in July 1995 deployed a NASA 

Tracking and Data Relay Satellite. STS-88 in December 1998 brought the first U.S. 

element, the Unity Node, to the space station. 

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Mission Specialist 3: Richard Linnehan

Richard M. Linnehan, 44, a doctor of veterinary medicine, was 

selected as an astronaut in 1992 after service in the Army 

Veterinary Corps. Much of his service was with the Naval Ocean 

Systems Center in San Diego, where he served as chief clinical 

veterinarian for the Navy’s Marine Mammal Program. On STS-109 

he will team with Grunsfeld to do three spacewalks. He will be a 

coordinator for the flight’s other two spacewalks. During the 

rendezvous, he will operate a handheld laser range-finding device, 

aiming it through the shuttle windows at the Hubble Space 

Telescope to provide Commander Altman with supplementary 

distance and closing rate information. Other responsibilities include 

opening and closing of Columbia’s payload bay doors, serving as one of two medics on 

board and serving as entry mission specialist. 

Linnehan has served as a mission specialist on two space flights. His first flight was STS78, a 17-day Spacelab life sciences and microgravity studies mission in June and July 

1996. He also flew on STS-90, the 16-day Neurolab mission in April and May 1998. 

Mission Specialist 4: James Newman

James H. Newman holds a Ph.D. in physics from Rice University 

and is a veteran of three space flights and four spacewalks. After 

graduation from Rice he did a year of postdoctoral studies there in 

atomic and molecular physics. Then, in 1985, he was named a 

Rice adjunct professor. That year he also began work at Johnson 

Space Center in crew and flight control team training in propulsion 

systems. He was named an astronaut in 1990. On STS-109 

Newman will perform two spacewalks and be a coordinator for the 

mission’s other three spacewalks. He is also responsible for postinsertion coordination and the on-board laptop computers. 

Newman first flew on STS-51, a 10-day flight in September 1993, which deployed the 

Advanced Communications Technology Satellite and the Orbiting and Retrievable Far and 

Extreme Ultraviolet Spectrometer on the SPAS satellite. STS-69 was an 11-day mission in 

September 1995 that deployed and retrieved a SPARTAN satellite and the Wake Shield 

Facility. In December 1998, Newman performed three spacewalks on STS-88 / 2A, a 12-

day mission that was the first assembly flight for the International Space Station. 

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Mission Specialist 5: Michael Massimino

Michael J. Massimino, 39, received a doctorate in mechanical 

engineering in 1992 from Massachusetts Institute of Technology, 

where his work on human-operator-controlled space robotics 

systems resulted in two patents. After graduation he worked for 

McDonnell Douglas Aerospace in Houston and also served for 

three years as an assistant adjunct professor at Rice University. He 

became an assistant professor at Georgia Institute of Technology 

in 1995 and was selected as an astronaut in 1996. He will make 

two of the mission’s spacewalks with James Newman and serve as 

a coordinator of the other three. He also will have backup robotic 

arm responsibilities. 

Massimino is making his first space flight. 

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Flight Day Summary Timeline 

DATE TIME (EST) DAY MET EVENT 

02/28/02 6:48:00 AM 1 000/00:00 Launch 

02/28/02 7:33:00 AM 1 000/00:45 OMS 2 Burn 

02/28/02 11:29:00 AM 1 000/04:41 NC1A Burn 

02/28/02 12:16:00 PM 1 000/05:28 NC1B Burn 

03/01/02 1:06:00 AM 2 000/18:18 NC2 Burn 

03/01/02 5:28:00 AM 2 000/22:40 NPC Burn 

03/01/02 10:29:00 AM 2 001/03:41 NH/NC3 Burn 

03/02/02 12:36:00 AM 3 001/17:48 NC4 Burn 

03/02/02 2:12:00 AM 3 001/19:24 Ti Burn 

03/02/02 4:25:00 AM 3 001/21:37 HST Grapple 

03/03/02 1:53:00 AM 4 002/19:05 EVA-1 Start 

03/04/02 1:53:00 AM 5 003/19:05 EVA-2 Start 

03/05/02 12:53:00 AM 6 004/18:05 EVA-3 Start 

03/06/02 6:53:00 AM 7 005/19:05 EVA-4 Start 

03/07/02 6:53:00 AM 8 006/19:05 EVA-5 Start 

03/08/02 5:15:00 AM 9 007/22:27 HST Release 

03/10/02 7:13:00 AM 11 010/00:25 HP Adjust 

03/11/02 2:29:00 AM 12 010/19:41 Deorbit Burn 

03/11/02 3:38:00 AM 12 010/20:50 Landing 

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Payloads 

Advanced Camera for Surveys 

With the addition of the Advanced Camera for Surveys (ACS), Hubble’s new scientific 

instrument, astronomers will have the opportunity to discover celestial objects far beyond 

the reach of current instruments in a fraction of the time, unlocking more of the Universe’s 

secrets. The ACS can survey a field on the sky twice as large as the original Hubble Deep 

Field, to the same exposure depth, three to four times faster than the camera that took the 

original Hubble Deep Field observations, the Wide Field and Planetary Camera 2 

(WFPC2). A deep "core sample," looking back in time to shortly after stars and galaxies 

began to form, requires about 10 days of dedicated Hubble observing with the WFPC2, but 

less than three days with the ACS. This higher efficiency will allow Hubble to survey more 

areas of the sky or perform additional scientific observations in the same amount of time, 

greatly improving the productivity of this precious astronomical resource. 

Astronauts will install ACS into the location currently held by the Faint Object Camera—the 

last of Hubble’s original instruments. ACS will become Hubble’s new workhorse, surveying 

far regions of the Universe, searching for extra-solar planets, and observing weather and 

other features on planets in our own solar system. With its wider field of view, superb image 

quality, and exquisite sensitivity, ACS will take full advantage of Hubble’s unique position 

as a space-based telescope. This instrument is sensitive to wavelengths ranging from 

ultraviolet to the far red (115-1050 nanometers). 

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ACS is a large phone-booth-sized instrument consisting of three different, specialized 

channels. Each channel plays a unique imaging role, enabling ACS to contribute to many 

different areas of astronomy and cosmology. The ACS was manufactured by Ball 

Aerospace and Technologies Corp. in Boulder, Colo.

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Wide Field Channel: Surveying the Universe 

The Wide Field Channel will conduct vast sky surveys to study the nature and distribution 

of galaxies. It was designed with a wide field of view to search for galaxies and clusters of 

galaxies in the early Universe, helping astronomers understand how our Universe evolved. 

Its field of view is Hubble’s largest ever--more than twice the size of Hubble’s current 

surveyor, WFPC2. 

ACS’s Wide Field Channel holds two state-of-the-art, 8-million pixel detectors called charge 

coupled devices (CCDs). These CCDs collect the light from astronomical objects and 

record their images. Designed to collect the most light in the shortest time possible, the 

Wide Field Channel uses highly reflective, silver-coated mirrors and an enhanced antireflection coating on its CCD detectors. This design allows this channel to collect four and a 

half times more light in a given exposure time than any of its predecessors. The Wide Field 

Channel is optimized to detect red light (600-800nm), which allows it to observe very old, 

very distant objects whose spectra are red-shifted due to the expansion of the Universe. 

High Resolution Channel: Capturing the Details 

The High Resolution Channel will take extremely detailed pictures of the inner regions of 

galaxies, and search neighboring stars for planets and planets-to-be. This channel uses a 

one-million-pixel CCD, and a coronagraph to suppress light from bright objects, enabling 

astronomers to view nearby faint objects. Scientists will use this capability to examine the 

galactic neighborhoods around bright quasars. 

The High Resolution Channel will also polarize and disperse light. These functions will 

allow Hubble users to study light in the centers of galaxies with massive black holes, as 

well as ordinary galaxies, star clusters, and gaseous nebulae. 

Solar Blind Channel: Seeing in Ultraviolet 

The Solar Blind Channel is sensitive to only the shorter wavelengths of ultraviolet light. 

Some features—such as emission lines that indicate the presence of certain molecules—

can be detected only in the ultraviolet portion of the spectrum. The Solar Blind Channel 

uses a highly sensitive photon-counting detector to enhance the visibility of these features. 

It will search for hot stars and quasars, and will study aurora and weather on planets in our 

own solar system. 

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Payloads 

Power Control Unit 

The Power Control Unit (PCU) is Hubble’s power switching station. As the central controller 

of the telescope’s electrical system, it regulates and distributes the power Hubble needs to 

operate. 

Shown open here, the Power Control Unit will be replaced on this mission, 

requiring Hubble to be powered down. 

Hubble’s solar arrays collect sunlight and convert it into electrical energy. The PCU 

distributes this energy from the solar arrays to the batteries and electrical components on 

Hubble, including the science instruments. The electrical energy stored in the six on-board 

batteries is used when Hubble travels into the Earth’s shadow each orbit. The PCU also 

safeguards Hubble from power spikes and controls battery charging. 

The new PCU replaces the original flight unit in Bay 4 of the telescope. It weighs 

approximately 160 pounds and measures 45 in. x 24 in. x 12 in. Designed and built by 

Lockheed Martin Space Systems in Sunnyvale, Calif., the new PCU is the original flight 

spare built for Hubble. This unit has been modified and retested to ensure optimal 

performance, and to enhance ease of installation by the astronauts. 

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The original PCU has been on the job continuously since Hubble’s launch in 1990 and had 

experienced normal degradation as it aged. Several relays that control battery charging 

and power distribution have failed and an electrical joint in the box has loosened, causing a 

slight loss of power and a risk of battery overheating. With Hubble’s mission extended to 

2010, a fresh PCU will enable Hubble to remain healthier and more productive throughout 

its lifetime. 

The telescope’s planners did not originally design the PCU to be replaced. Late in the 

building of Hubble, engineers made minor modifications to create a somewhat more 

astronaut-friendly PCU. Nevertheless, replacing the PCU will be a challenging spacewalk. 

Astronauts must disconnect 36 connectors on the original PCU and reconnect them to their 

proper mates on the new unit. The change-out of the PCU requires Hubble to be powered 

off for the first time since its launch in 1990. All telescope subsystems, including thermal 

control, will be turned off during this time. 

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Payloads 

NICMOS Cryocooler 

During the mission, astronauts will install a new cooling system, the NICMOS Cryocooler, 

onto the Near Infrared Camera and Multi-Object Spectrometer (NICMOS), which has been 

dormant since January of 1999. 

Installed on Hubble in February of 1997, NICMOS used infrared vision to explore dark, 

dusty regions of space with precise optical clarity. Its infrared detectors operated at a very 

cold temperature (minus 352 degrees Fahrenheit, which is minus 213 degrees Celsius, or 

60 degrees Kelvin). NICMOS was encased in a container filled with solid nitrogen ice to 

keep the detectors cold. A small heat leak caused the nitrogen ice to be consumed more 

quickly than planned. 

The NICMOS Cooling System will allow Hubble’s Near-Infrared Camera to be 

reactivated. 

Scientists and engineers at NASA’s Goddard Space Flight Center in Greenbelt, Md., 

devised the NICMOS Cryocooler, a state-of-the-art cryogenic cooler that is expected to 

return NICMOS to active duty. Creare Inc., Hanover, N.H., manufactured the tiny turbomachinery. 

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By using non-expendable neon gas as a coolant, this closed system delivers high cooling 

capacity, extremely low vibration and high reliability. It uses a miniature cryogenic circulator 

to remove heat from NICMOS and transport it to the cryocooler. At the heart of the cooler is 

a turbo-machine consisting of a compressor that uses a tiny turbine turning at up to 

400,000 rpm (about 100 times the operating speed of a typical car engine). The NICMOS 

Cryocooler is virtually vibration-free—an important aspect for Hubble since vibrations affect 

image quality. 

The new cryogenic system is expected to re-cool the NICMOS infrared detectors to about 

minus 334 degrees Fahrenheit (minus 203 degrees Celsius or 70 degrees Kelvin). This is 

an ideal temperature for the detectors and will make NICMOS more sensitive to incoming 

light. 

This new technology was successfully demonstrated in 1998 aboard the Space Shuttle 

Discovery on STS-95. Retrofitting NICMOS with the new cryocooler can potentially double 

the instrument’s lifetime. 

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Payloads 

Hubble’s New Solar Arrays 

Astronauts will give Hubble a new look and boost its power when they install new solar 

arrays on the telescope. Unlike Hubble’s first two pairs, which are so flexible that they roll 

up like window shades, Hubble’s newest solar arrays are flat and rigid and fold up rather 

than roll up. 

The new arrays have one-third less solar cell area, but produce 20 percent more power 

than the current set. The added power enables all the science instruments to be powered 

and ready to operate simultaneously, allowing for more discoveries in less time. 

The high efficiency solar panels have supporting frames made of aluminum-lithium, which 

is stronger and lighter than the type of aluminum commonly used in spacecraft 

construction. The supports are less sensitive to the extreme temperature changes of 

Hubble's harsh environment. 

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One wing of Solar Array 3 is lowered into a chamber for testing. 

The new rigid arrays will produce 20 percent more power. 

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During each 97-minute orbit, Hubble spends about two-thirds of its time in searing sunlight 

and the other third in the frigid darkness of Earth's shadow. The rapidly cycling conditions 

cause the temperature of the solar panels to fluctuate between minus 94 degrees 

Fahrenheit (minus 70 degrees Celsius) and 187 degrees Fahrenheit (86 degrees Celsius). 

The solar arrays reach their hottest temperature just 10 minutes after leaving the chill of 

Earth's shadow. 

Such dramatic, repeated temperature changes can cause tiny vibrations and movements 

within a spacecraft’s solar array structure. If these movements are large enough, they 

cause motion of the main body of the telescope, and may affect the sensitivity of Hubble’s 

pointing control instruments and interfere with long-term science observations. 

The smaller, stiffer arrays are easier for the astronauts to work around during servicing 

missions—easier to fold up and move out of their way. In addition, their smaller size 

decreases on-orbit drag and slows the rate at which Hubble’s orbit decays. Over time, all 

low Earth orbiting satellites feel the effects of atmospheric drag and lose altitude. The new 

arrays will slow that rate of altitude loss. 

The Hubble program bought the new solar panels from the production line of a commercial 

system of communications satellites. At NASA’s Goddard Space Flight Center in Greenbelt, 

Md., four of these panels were attached to an aluminum-lithium support wing structure to 

create each of the complete structures called “wings.” A total of eight panels were used in 

the construction of these two wings. Goddard Hubble team members fabricated the support 

wing structures, the composite mast assembly, and the electrical assembly for these wings. 

The European Space Agency (ESA) built Hubble’s first two sets of solar arrays. For the 

newest pair, ESA designed, developed and tested the Solar Array Drive Mechanisms, 

which maneuver the arrays to keep them constantly pointed at the Sun. 

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Payloads 

Reaction Wheel Assembly 

One of four reaction wheel assemblies (RWAs), which are an important part of Hubble's 

Pointing Control Subsystem (PCS), will be replaced by a new unit on SM3B. Reaction 

wheels and their associated electronics are packaged as RWAs. The RWAs use rotational, 

or angular momentum, to move the telescope from one target to another (this motion is 

called "slewing"), and to keep it pointed steadily once the target is acquired in the aperture 

of the observing scientific instrument. 

Reaction Wheel Assembly 

The flywheel inside each RWA can spin at speeds up to 3,000 revolutions per minute. 

Three RWAs are required for scientific operations, but the PCS system works better if all 

four wheels are operating. In particular, the slew times are reduced if four, rather than 

three, wheels are functioning, thereby improving Hubble’s observing efficiency. 

On Nov. 10, 2001, one of Hubble's four reaction wheels (RWA1) experienced a sevenminute telemetry dropout during which the wheel's rotation speed was unknown both to the 

automated systems on board Hubble and to engineers on the ground. Associated with this 

event were two brief disturbance torques to the telescope itself. Telemetry resumed at the 

end of the seven-minute period, and there have been no further anomalies in the wheel. 

Hubble continues to function well and was not damaged during the seven-minute event. 

Because of the importance of reaction wheels to the telescope's performance, and taking 

into account the two-year time period between SM3B and SM4, it was decided to add a 

spare RWA to the manifest of SM3B. The STS-109 astronauts will swap out RWA1 with the 

new RWA during the second spacewalk, or EVA. 

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Rendezvous 

Hubble Space Telescope 

Rendezvous, Capture, Berthing and Deploy 

Columbia's rendezvous with the Hubble Space Telescope actually begins with the precisely 

timed launch of the shuttle on a course for the orbiting telescope. During the first two days 

of the mission, periodic engine firings will gradually bring Columbia to a point about 9 1⁄2 

statute miles behind the telescope, the starting point for a final approach to the observatory. 

Before the approach, Mission Control, Houston, in concert with the Space Telescope 

Operations Control Center at the Goddard Space Flight Center in Greenbelt, Md., will 

command the telescope to stow the High Gain Antennas and close the aperture door. 

About 2 1⁄2 hours before the planned capture time on Flight Day Three, Columbia will reach 

that point about 50,000 feet – 9 1⁄2 statute miles -- behind HST. At that time, Columbia's jets 

will be fired in a Transition Initiation (TI) burn to begin the final phase of the rendezvous. 

Columbia will close the final miles to the telescope during the next orbit of Earth. About five 

minutes before the terminal initiation burn, Mission Specialist Nancy Currie will power up 

Columbia's robotic arm, releasing it from its latches along the left-hand edge of the shuttle's 

payload bay. 

As Columbia closes in the final miles, the shuttle’s rendezvous radar system will begin 

tracking HST and providing range and closing rate information to the crew. During the 

approach toward the telescope, the shuttle will have an opportunity to conduct four, small 

mid-course corrections at regular intervals. As the shuttle closes in, Currie will maneuver 

the robotic arm up above the payload bay of Columbia to a position where it is poised to 

latch on to a capture fixture on the telescope. 

Just after Columbia’s fourth small course correction engine firing is completed, the shuttle 

will reach a point about a half-mile below the telescope. At that time, about an hour before 

the scheduled docking, Commander Scott Altman will take over manual control of the 

approach. During the rendezvous, Pilot Duane Carey will assist Altman with navigation. 

Mission Specialist Rick Linnehan will operate a handheld laser range-finding device, aiming 

it through the shuttle windows at the telescope to provide Altman with supplementary 

distance and closing rate information. Mission Specialist Jim Newman will oversee a laptop 

computer program aboard Columbia, fed by real-time navigation information, which will 

provide Altman with additional cues to aid in controlling his approach. 

Altman will slow Columbia's approach and fly up toward the telescope. When he is within 

1,500 feet of the observatory, Altman will switch the shuttle's thrusters to a mode called 

“low-Z.” In that mode, jets offset to the direction of the telescope are fired to continually 

slow the shuttle's approach, avoiding potential contamination of HST by shuttle jet exhaust. 

As Columbia moves within 600 feet of HST, it will approach the telescope at less than a 

half-mile per hour. As the distance between Columbia and HST decreases to about 200 

feet, the space telescope operations ground crew will command HST to perform a final roll 

maneuver to position itself for capture. The telescope’s solar arrays will remain fully 

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deployed parallel to Hubble’s optical axis. The shuttle will creep toward the observatory as 

it closes the final 100 feet, moving at a speed of only a few feet per minute. 

Altman will fly Columbia to within 35 feet of the telescope and hold position while Currie, 

using a view from a camera mounted at the end of the robotic arm to gauge alignment, 

latches on to the telescope. 

Using views from a camera centered in the ring where the telescope will be berthed in the 

shuttle bay, Currie will then lower HST into a special cradle, called the Hubble Space 

Telescope Flight Support System, in Columbia’s payload bay. The telescope will be latched 

to the FSS for the duration of the servicing work. An umbilical from Columbia will be 

remotely connected to HST to provide transmission of electrical power from the shuttle to 

the telescope. Then, Altman will maneuver the shuttle to allow HST’s solar arrays to track 

the sun, fully charging the telescope's batteries. 

About 4 1⁄2 hours after HST is captured, once the batteries are fully charged, commands will 

be sent to retract the telescope's solar arrays. During the servicing work, the HST FSS 

cradle can be rotated and pivoted as needed to provide the best available access to 

various worksites for spacewalkers or to prepare for a reboost of the telescope by 

Columbia. About 4 1⁄2 hours after HST is captured, commands will be sent to retract the 

telescope's solar arrays for a final time. 

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Hubble Space Telescope Deploy 

The Hubble Space Telescope is planned to be released from Columbia on Flight Day Nine 

of the mission. About three hours before the planned release time that day, Currie will 

power up Columbia's robotic arm and latch on to the grapple fixture on the telescope. 

Telescope controllers will send commands to redeploy the high gain antennas. Columbia 

will be maneuvered to allow the new solar arrays to fully charge the HST batteries. About 

two hours before release, the telescope will be switched back to its own internal power and 

the umbilical attaching the telescope to Columbia's power system will be remotely 

disconnected. 

Then, the three latches that secure the telescope to the FSS in Columbia's payload bay will 

be released and Mission Specialist Michael Massimino, at the controls of the shuttle's 

robotic arm, will slowly maneuver the observatory to a point high above the shuttle bay. He 

will then hand robot arm operations to Currie. Columbia's steering jets will be turned off to 

avoid any possible disturbance as Currie commands the arm to release the telescope's 

fixture. Then, about a minute later, the shuttle jets will be turned back on and fired, again in 

the Low-Z mode to avoid contamination, to slowly back Columbia away. Another jet firing 

will be performed about a half-hour later to continue Columbia's separation from the vicinity 

of HST. 

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Spacewalks 

STS-109 Extravehicular Activity 

Astronauts John Grunsfeld, Rick Linnehan, Jim Newman and Michael Massimino will team 

up during STS-109 to perform five spacewalks, or Extravehicular Activities (EVAs), on 

consecutive days to maintain and upgrade the Hubble Space Telescope. The astronauts 

will perform the spacewalks in pairs on alternating days, providing each team a day to rest 

between ventures outside the shuttle. Grunsfeld and Linnehan will perform the first, third 

and fifth spacewalks. Newman and Massimino will perform the second and fourth 

spacewalks. Although not scheduled, resources are planned to be available for a sixth 

spacewalk to be conducted if needed to complete the planned telescope servicing tasks. 

For all of the spacewalks, Astronaut Nancy Currie will serve as prime robotic arm operator 

from controls in Columbia’s aft cockpit. Commander Scott Altman will be her backup. Currie 

will maneuver the arm to position the spacewalkers, one of whom will be working in a foot 

platform at the end of the arm the majority of the time. During the work outside, the 

astronauts can be identified by the markings on their spacesuits. 

Recognizing the spacewalkers: 

Grunsfeld, Extravehicular Crewmember 1 (EV1) -- solid red stripes on suit 

Linnehan, EV2 -- solid white suit (no stripes) 

Newman, EV3 – horizontal broken red stripes 

Massimino, EV4 -- diagonally broken red stripes 

Spacewalk Number One, Flight Day Four: Replace -V2 Solar Array and 

Diode Box Assembly, Install Diode Box Controller Cross Strap Harness 

Grunsfeld and Linnehan will begin the spacewalks with the first excursion outside of 

Columbia planned to occur on Flight Day Four of the mission, the day after Columbia 

captures the telescope. Planned to last 6 1⁄2 hours, the first spacewalk will include the 

replacement of one of the telescope’s two second-generation solar arrays (SA2), the array 

that will be on Columbia’s starboard side as the telescope is oriented in the shuttle bay. 

Both of the solar array wings will have been retracted the day before, about 4 1⁄2 hours after 

the telescope is latched in the shuttle payload bay. The SA2 array will be replaced with a 

third-generation array (SA3) that is more powerful and more durable. During most of the 

solar array work, the first 4 1⁄2 hours of the spacewalk, Linnehan will be working from the 

foot platform at the end of Columbia’s robotic arm. After that, Grunsfeld will work from the 

end of the arm and Linnehan will work free-floating. 

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STS-109

John Grunsfeld uses virtual reality hardware at the Johnson Space Center to 

rehearse some of his Hubble servicing tasks. 

To begin, Grunsfeld does various tasks to prepare for that day’s servicing activities. These 

include deploying the Axial Science Instrument Protective Enclosure (ASIPE) miniTranslation Aid (TA), deploying the port and starboard TAs as required, removing the 

Manipulator Foot Restraint (MFR) from its stowage location and installing it on the RMS 

grapple fixture, installing the Low Gain Antenna Protective Cover (LGAPC), removing the 

Berthing and Positioning System (BAPS) Support Post (BSP) from its stowage location and 

installing it on the Flight Support System (FSS), and inspecting the P105 and P106 

umbilical covers. Meanwhile, Linnehan brings out of the airlock the Crew Aids and Tools 

(CATs) and installs the MFR handrail to the MFR on the RMS. 

The BSP is required to dampen the vibration that the servicing activities will induce into the 

deployed SAs. Before the BSP installation, the crew will pivot the support structure to bring 

HST to an 85-degree angle. The two center push-in pull-out (PIP) pins are installed each 

day and removed each night in case the shuttle must make an emergency return to Earth. 

Grunsfeld removes the BSP from its stowage position in the FSS cradle, and then installs 

one end to the BAPS ring with a PIP pin and the aft end to the FSS cradle with another PIP 

pin. Finally the BSP is commanded to its 90-degree limit and the two center PIP pins are 

installed. 

After the initial setup, the spacewalkers will replace the -V2 Solar Array and Diode Box 

Assembly on the Telescope. They will also install the Diode Box Controller (DBC) crossstrap harness. First, Grunsfeld, who is free floating, retrieves the HST PFR and APE and 

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transfers them to Linnehan in the MFR. Linnehan moves to the HST and installs the PFR 

on HST foot restraint receptacle eight for Grunsfeld to use. Grunsfeld translates to the RAC 

to retrieve the DBC cross-strap harness and a Portable Connector Tray, and temporarily 

stows them on the telescope. Then he ingresses the PFR. Together the astronauts retract 

the -V2 SA2 Primary Deployment Mechanism (PDM). Grunsfeld then engages the PDM 

lock and installs the Portable Connector Tray. While still in the PFR, Grunsfeld demates the 

SA2 connectors from the DBA while Linnehan retrieves the WFPC Cover and installs it on 

the -V3 Aft Shroud in support of the PCU change-out on spacewalk number three. 

Next the astronauts remove the -V2 SA2 from the Telescope. They disengage the Solar 

Array Drive Adapter (SADA) Clamp, remove SA2, translate it to the RAC and install it on 

the starboard shelf via the SADA Clamp and forward constraint PIP pin mechanical 

attachments. 

Grunsfeld translates back to the telescope and removes the -V2 DBA by disengaging the 

remaining X-connector drive mechanism and releasing the four J-hook bolts while Linnehan 

retrieves the DBA2 from the RAC and carries it to Grunsfeld at the telescope worksite. The 

astronauts swap hardware and Grunsfeld installs the DBA2 on the telescope while 

Linnehan translates to the RAC with the DBA and installs it and closes its thermal cover. 

Grunsfeld installs the DBC cross-strap harness onto the telescope and mates it to the -V2 

DBA2. 

With the DBA2 now installed on the telescope, the astronauts begin the installation work for 

the new, third-generation solar array (SA3). Both translate to the RAC. Linnehan 

disengages Latch 5, deploys the mast and engages the two mast bolts. Grunsfeld 

ingresses the aft PFR, releases and pivots Latch 3 to clear the tang, disengages the two 

tang bolts, stows the tang and engages the two tang bolts. Linnehan disengages Latch 2. 

Grunsfeld pivots Latch 3 to the stowed position and installs the PIP pin, deploys the MLI 

flap over the tang interface and releases Latch 4. Grunsfeld stabilizes SA3 while Linnehan 

releases Latch 1. The astronauts then remove SA3 from the RAC. 

Both crewmembers install SA3 onto the telescope by properly orienting SA3 and inserting 

the SADA into the SADA Clamp until the three soft dock tangs engage. Grunsfeld engages 

the SADA Clamp closed and mates the SA3 electrical interfaces. Linnehan translates back 

to the RAC and performs the SA2 closeout work, engaging the aft latch, the forward latch 

and the two forward constraint bolts. 

Then the astronauts deploy the SA3 panel, engage the panel locking bolts and release the 

SA3 brake. Grunsfeld routes the DBC cross-strap harness to the +V2 side, removes the 

HST PFR and temporarily stows it on the ASIPE, and removes and stows a Portable 

Connector Tray on the RAC. Meanwhile, Linnehan maneuvers to the -V3 aft shroud and 

installs the two FHST covers in preparation for the PCU change-out on spacewalk three. 

At this time, the astronauts switch places: Grunsfeld ingresses the arm foot platform and 

Linnehan becomes the free floater. Linnehan translates to the ASIPE, retrieves the PFR 

from temporary stowage and transfers it to Grunsfeld, who installs it in foot restraint 

receptacle 19 in preparation for spacewalk two. Linnehan retrieves the Bay 10 Thermal 

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STS-109

Cover and installs it over Bay 10 of the Telescope while Grunsfeld disengages and 

removes the telescope’s +V2 trunnion EPS panel, mates the DBC cross strap harness and 

installs a MLI tent over the EPS panel cavity. 

For the daily closeout, Linnehan inspects the FSS main umbilical mechanism, disengages 

the two center PIP pins on the BSP, retracts the mini-TA, retracts the port and starboard 

TAs if required, and takes a tool inventory. Meanwhile, Grunsfeld prepares the CATs 

installed on the MFR handrail for return into the airlock and egresses the MFR. Linnehan 

releases the MFR safety tether from the grapple fixture for contingency Earth return. With 

that complete, the astronauts return to the airlock and Columbia’s cabin. 

Spacewalk Number Two, Flight Day Five: Replace +V2 Solar Array and 

Diode Box Assembly and Reaction Wheel Assembly-1 

For spacewalk two, Newman will be free floating and Massimino will work from the arm foot 

platform. The major objectives are to replace the +V2 Solar Array, the array oriented toward 

Columbia’s port side, and the Diode Box Assembly on the telescope and complete the DBC 

installation by mating it to the +V2 SA3. They also will replace the Reaction Wheel 

Assembly – 1 (RWA-1). 

Fewer daily setup tasks are required for spacewalk two than for spacewalk one. After 

completing the airlock egress procedure, Newman reconnects the safety strap on the MFR, 

installs the two BSP center PIP pins and deploys the mini-TA. Massimino exits the airlock 

with the spacewalk two required CATs installed on the MFR handrail and installs the MFR 

handrail. 

After completing the daily setup tasks, the astronauts begin the tasks for the +V2 Solar 

Array and Diode Box Assembly change-outs, which are similar to the -V2 Solar Array 

and Diode Box Assembly change-outs performed during the first spacewalk. First, 

Newman and Massimino retrieve the HST PFR and APE and install them on HST foot 

restraint receptacle 19. Newman translates to the RAC to retrieve a Portable Connector 

Tray and temporarily stows it on the telescope. Then he ingresses the PFR. 

Together the astronauts retract the +V2 SA2 PDM. Newman then engages the PDM lock 

and installs the Portable Connector Tray. Still in the PFR, Newman demates the SA2 

connectors from the DBA while Massimino disengages five of six bolts on each door of 

HST Bays 2, 3 and 4 in support of the PCU change-out during the third spacewalk. 

Next, the astronauts remove the +V2 SA2 from the telescope. They disengage the 

SADA Clamp, remove SA2, translate it to the RAC and install it on the port shelf via the 

SADA Clamp and forward constraint PIP pin mechanical attachments. 

Newman translates back to the telescope and removes the +V2 DBA by disengaging the 

remaining X-connector drive mechanism and releasing the four J-hook bolts while 

Massimino retrieves the DBA2 from the RAC and translates it to Newman at the telescope 

worksite. The astronauts swap hardware and Newman installs the DBA2 on the telescope 

while Massimino translates to the RAC with the DBA and installs it and closes its thermal 

cover. 

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STS-109

With the +V2 DBA2 now installed on the telescope, they begin installation work for the 

replacement Solar Array (SA3). Both astronauts translate to the RAC. Massimino 

disengages Latch 5, deploys the mast, and engages the two mast bolts. Newman 

ingresses the forward PFR, releases and pivots Latch 3 to clear the tang, disengages the 

two tang bolts, stows the tang and engages the two tang bolts. Massimino disengages 

Latch 2. Newman pivots Latch 3 to the stowed position and installs the PIP pin, deploys the 

MLI flap over the tang interface and releases Latch 4. Newman stabilizes SA3 while 

Massimino releases Latch 1. Both remove SA3 from the RAC. 

Working together, the astronauts install SA3 onto the telescope by properly orienting SA3 

and inserting the SADA into the SADA Clamp until the three soft dock tangs engage. 

Newman engages the SADA Clamp closed and mates the SA3 electrical interfaces, then 

mates the DBC cross-strap harness to the +V2 DBA2. Massimino translates back to the 

RAC and performs the SA2 closeout work: engaging the aft latch, the forward latch and the 

two forward constraint bolts. 

Both astronauts work together again to deploy the SA3 panel, engage the panel locking 

bolts and release the SA3 brake. Newman removes the HST PFR and APE and stows 

them on the FSS, and removes and stows the Portable Connector Tray on the RAC. 

Upon completion of the SA changeout task, the spacewalkers will replace the RWA-1. 

Newman translates to the Large Orbital Replacement Unit Protective Enclosure (LOPE) on 

the aft starboard side of the Multi-Use Lightweight Equipment (MULE), opens the lid, 

removes the two RWA1-R wing tab connectors from the LOPE pouch and secures them to 

the RWA1-R handle Velcro, disengages the three keyway bolts, removes the replacement 

RWA-1 (RWA1-R), and translates to the top of the starboard MULE. 

Massimino maneuvers to Bay 6 and opens the Bay 6 door, demates the two RWA-1 wing 

tab heater connectors from the heater bracket, demates the two RWA-1 wing tab 

connectors from RWA-1, disengages the three RWA-1 keyway bolts, and removes RWA-1 

from HST Bay 6. Then he maneuvers to the starboard MULE location and performs a 

RWA swap with Newman. Massimino then maneuvers with RWA1-R to the Bay 6 worksite, 

installs it on HST, engages the three keyway bolts, and mates the four wing tab electrical 

connectors. Then he closes the Bay 6 door. 

Newman, after transferring the RWA1-R to Massimino and receiving RWA-1, translates 

back to the LOPE, installs the RWA-1 in the LOPE, engages the three keyway bolts, stows 

the two wing tab connectors in the LOPE pouch, and closes the LOPE lid. 

Newman retrieves the Bay 5 Thermal Cover and installs it in the retracted position on the 

HST Bay 5 in preparation for the PCU change-out on spacewalk three. Newman also 

retrieves the doorstop extensions and installs them on the +V2 aft shroud doorstops in 

preparation for the NCS Radiator installation on spacewalk five. 

For the daily closeout, Newman inspects the FSS main umbilical mechanism, disengages 

the two center PIP pins on the BSP, retracts the mini-TA, retracts the port and starboard 

TAs if required and takes a tool inventory. Meanwhile, Massimino prepares the CATs 

installed on the MFR handrail for return into the airlock and egresses the MFR. Newman 

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STS-109

releases the MFR safety tether from the grapple fixture for contingency Earth return. Then 

the astronauts return to the airlock and Columbia’s cabin. 

Spacewalk Number Three, Flight Day Six: Replace Power Control Unit 

(PCU) 

During the third spacewalk, Grunsfeld and Linnehan will replace the PCU in HST Bay 4. 

They begin the spacewalk with Grunsfeld free floating and Linnehan working from the arm 

foot platform but switch places after about three hours. The third spacewalk is planned to 

last about seven hours. 

After they exit the airlock, Grunsfeld reconnects the safety strap on the MFR, installs the 

two BSP center PIP pins and deploys the mini-TA. Linnehan exits the airlock with the 

spacewalk three required CATs installed on the MFR handrail and installs the MFR 

handrail. 

Both astronauts complete the daily setup tasks, and then begin the PCU change-out. 

Grunsfeld translates to the RAC to retrieve the Power Distribution Unit (PDU) fuse plug 

caddy and battery stringers and transfers them to Linnehan. Linnehan translates to HST 

Bay 3, opens the bay door, demates the three battery connectors, installs caps to deadface 

the battery power and temporarily closes the door. He then translates to Bay 2 and 

performs the same procedure for the Bay 2 battery. 

Meanwhile, Grunsfeld translates to Bay 5 and deploys the thermal cover, retrieves the DBA 

thermal cover, translates to the +V2 DBA2 and installs its thermal cover. Then he translates 

to Bay 10 and deploys the thermal cover, retrieves the DBA thermal cover, translates to the 

-V2 DBA2 and installs its thermal cover. Grunsfeld deploys the FHST covers on the 

telescope, then translates to the SAC, retrieves the Harness Retention Device and 

transfers it to Linnehan at the Bay 4 worksite. 

Linnehan opens the Bay 4 door and installs the Harness Retention Device and door stay. 

Linnehan then removes the six in-board PDU Fuse Plugs to gain sufficient access to the 

PCU connectors on the left side. Grunsfeld retrieves the PCU handhold from the SAC and 

temporarily stows it by the +V2 trunnion. Then he translates to the airlock and recharges 

his suit with oxygen, enabling him to extend his EVA time. Linnehan disengages seven of 

10 PCU keyway bolts and demates all but the last six connectors. 

At this point, Grunsfeld and Linnehan switch places: Grunsfeld begins work from the arm 

foot platform and Linnehan works free-floating for the remainder of the spacewalk. 

Grunsfeld completes demating the remaining PCU connectors, installs the PCU handhold, 

disengages the three remaining bolts, disengages the PCU ground strap and removes the 

PCU from the telescope. 

Linnehan translates to the starboard SAC where the replacement PCU (PCU-R) is located, 

ingresses the PFR, opens the thermal cover, disengages the six keyway bolts and removes 

the PCU-R from the SAC. Linnehan and Grunsfeld swap boxes at the SAC worksite. 

Grunsfeld translates with the PCU-R back to the telescope worksite, installs it, engages 

seven keyway bolts and engages the ground strap. Linnehan stows the PCU on the SAC, 

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STS-109

engages the six keyway bolts, retightens the two PCU handhold wing bolts, egresses the 

PFR and reinstalls the PCU thermal cover. He then translates to the airlock and recharges 

his suit with oxygen. Grunsfeld mates the 36 connectors on the PCU-R, a difficult and timeconsuming task. 

Linnehan inspects the HST exterior handrails to be used for the ACS and NCS tasks on the 

fourth and fifth spacewalks, and, if required, installs handrail covers. Grunsfeld reinstalls 

the PDU fuse plugs, removes the Harness Retention Device, removes the door stay, and 

closes the HST Bay 4 door with one J-bolt. He re-opens the Bay 3 door, remates the 

battery connectors and closes the door with one J-bolt. Then he performs the same 

procedure for the Bay 2 battery. After the PDU fuse plugs are reinstalled, Linnehan 

translates to the +V2 DBA2, retrieves the thermal cover, stows it on its Bay 5 thermal cover 

stowage pouch and retracts the Bay 5 thermal cover. He translates to the -V2 DBA2, 

retrieves the thermal cover, stows it on its Bay 10 thermal cover stowage pouch and 

retracts the Bay 10 thermal cover. Next, Linnehan retrieves the Harness Retention Device 

and stows it on the SAC. Then, he retracts the FHST covers, receives the PDU fuse plug 

caddy and battery stringers from Grunsfeld, and stows them on the RAC. If time allows, 

Grunsfeld removes the WFPC thermal cover and stows it on the SAC. 

For the daily closeout, Linnehan inspects the FSS main umbilical mechanism, disengages 

the two center PIP pins on the BSP, retracts the mini-TA, retracts the port and starboard 

TAs if required and takes a tool inventory. Meanwhile, Grunsfeld prepares the CATs 

installed on the MFR handrail for return into the airlock and egresses the MFR. Linnehan 

releases the MFR safety tether from the grapple fixture for contingency Earth return. Then 

the astronauts return to the airlock, completing the third spacewalk. 

Spacewalk Number Four, Flight Day Seven: Replace Faint Object Camera 

with the Advanced Camera for Surveys, Install Electronics Support Module 

and Perform Power Control Unit Cleanup Tasks 

On the fourth spacewalk, Newman begins work in the arm foot platform and Massimino 

works free-floating. The two spacewalkers switch work locations about halfway through the 

planned 6 1⁄2 -hour spacewalk. The major objectives are to replace the Faint Object Camera 

(FOC) with the new Advanced Camera for Surveys (ACS), an instrument with 10 times the 

discovery power; install an Electronics Support Module (ESM), part of NICMOS cryocooler 

installation the next day, in the telescope’s aft shroud; and do the remaining PCU cleanup 

tasks. After exiting the airlock, Massimino reconnects the safety strap on the MFR, installs 

the two BSP center PIP pins and deploys the mini-TA. Newman exits the airlock with the 

spacewalk four required CATs installed on the MFR handrail and installs the MFR handrail. 

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Electronic Support Module (ESM). 

The astronauts complete the daily setup tasks, and then begin the FOC/ACS change-out. 

Massimino deploys the aft fixture, retrieves the COSTAR Y-harness from the RAC port 

ATM and stows it on the telescope aft shroud. Newman opens the -V2 aft shroud doors. 

Massimino and Newman work together to remove the FOC from HST. Massimino demates 

the four FOC connectors, disconnects the FOC purge line and disconnects the ground 

strap. Newman disengages the FOC A-Latch and Massimino disengages the FOC B-Latch. 

Then Newman removes the FOC from the telescope and stows it on the aft fixture. 

Massimino and Newman now work together to install the Cross Aft Shroud Harness 

(CASH). Even though the CASH is part of the NCS installation, it is installed now for 

maximum efficiency. Its early installation eliminates the need to open the -V2 aft shroud 

doors a second time during the fifth spacewalk. Massimino and Newman retrieve the CASH 

from the SAC and install it on handrails inside the aft shroud. 

Massimino and Newman retrieve the ACS from the ASIPE. Massimino configures the aft 

ASIPE PFR, opens the ASIPE lid, disconnects the ACS ground strap and deploys the BLatch alignment aid. Newman disengages the A-Latch and Massimino disengages the BLatch. They both remove the ACS from the ASIPE. Massimino closes the ASIPE lid and 

engages one lid latch to maintain thermal stability inside the ASIPE. The astronauts 

continue to work together to install the ACS into the telescope aft shroud. They insert the 

ACS along the guide rails, deploy the B-Latch alignment aid arm, engage the B-Latch and 

A-Latch, stow the alignment aid, tether the ESM ground strap to the ACS handrail, reinstall 

the HST ground strap and mate the four ACS connectors. 

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Next the astronauts install the FOC into the ASIPE. Newman retrieves the FOC from the aft 

fixture while Massimino re-opens the ASIPE lid. Newman inserts the FOC into the ASIPE 

guide rails while Massimino stows the aft fixture and engages the FOC B-Latch. Newman 

engages the A-Latch. Massimino disengages the FOC ground strap bolt and installs the 

ground strap on FOC, then closes the ASIPE lid and engages the five lid latches. 

After completing the FOC installation into the ASIPE, the astronauts switch work locations, 

with Massimino climbing into the arm foot platform and Newman becoming the free-floating 

spacewalkers. Then they retrieve the ESM from the MULE and install it in the -V2 aft 

shroud. They install the ACS ESM ground strap on the ESM, retrieve the Y-harness from 

temporary stowage, demate the four COSTAR connectors, mate four Y-harness connectors 

to the COSTAR harnesses, mate four Y-harness connectors to COSTAR and mate four Yharness connectors to the ESM. Massimino mates the four CASH connectors to the ESM. 

Now they are ready to close the -V2 aft shroud doors. 

The PCU cleanup task follows the FOC/ACS change-out and the ESM installation. 

Newman removes the Bay 10 thermal cover and stows it on the ASIPE, then removes the 

Bay 5 thermal cover and stows it on the ASIPE. He also articulates the aft ASIPE PFR to its 

landing configuration. Meanwhile, Massimino engages the remaining 5 J-bolts on each 

door of Bays 2, 3 and 4. Then the astronauts remove the FHST and WFPC covers from the 

telescope and stow them on the SAC. 

For the daily closeout, Newman inspects the FSS main umbilical mechanism, disengages 

the two center PIP pins on the BSP, retracts the mini-TA, retracts the port and starboard 

TAs if required and takes a tool inventory. Meanwhile, Massimino prepares the CATs 

installed on the MFR handrail for return into the airlock and egresses the MFR. Newman 

releases the MFR safety tether from the grapple fixture for contingency Earth return. Then 

they reenter the airlock and Columbia, completing the spacewalk. 

Spacewalk Number Five, Flight Day Eight: Install the Near-Infrared Camera 

and Multi-Object Spectrometer (NICMOS) Cryogenic Cooler and NICMOS 

Cooling System Radiator 

During the fifth spacewalk, Grunsfeld will begin work from the arm platform and Linnehan 

will work free-floating. They will switch locations halfway through the seven-hour 

spacewalk. The major objectives are to install the NICMOS Cooling System, a NICMOS 

Cryogenic Cooler (NCC) and NICMOS Cooling System (NCS) Radiator. After they exit the 

airlock, Linnehan reconnects the safety strap on the MFR, installs the two BSP center PIP 

pins, and deploys the mini-TA. Grunsfeld exits the airlock with the spacewalk five CATs 

installed on the MFR handrail and installs the MFR handrail. 

Both astronauts complete the daily setup tasks, and then begin the NCS installation. 

Grunsfeld opens the telescope’s +V2 aft shroud doors while Linnehan retrieves the Cryo 

Vent Line (CVL) bag and NCS sock bag from the RAC port ATM and the NCC ground strap 

and cryo vent insert from the RAC starboard ATM. Together the astronauts prepare the 

NICMOS for the NCS installation. They remove the NICMOS CVL and stow it in the CVL 

bag, close the NICMOS vent line valve, disengage the NICMOS ground strap from 

NICMOS, install the NCC ground strap adapter on NICMOS and install the cryo vent insert. 

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Linnehan retrieves the P600 harness from the RAC starboard ATM. Grunsfeld retrieves the 

NCC from the SAC and opens the neon bypass valve while Linnehan closes the NCC 

contamination cover. 

Both astronauts install the NCC into the HST aft shroud. Grunsfeld installs the NCC ground 

strap on NCC and mates the four CASH connectors. Linnehan translates to the MULE and 

releases some of the NCS Radiator latches and shear ties. At this point, they switch 

locations, with Linnehan working from the arm foot platform and Grunsfeld free-floating for 

the remainder of the spacewalk. 

Next comes retrieval of the NCS Radiator. Grunsfeld closes the left aft shroud door and 

together with Linnehan disengages the remaining latches, removes the NCS Radiator from 

the MULE and opens the NCS Radiator handrail latches. They install the NCS Radiator 

onto the exterior of the telescope aft shroud. 

Grunsfeld prepares the NCC by installing the coolant-in and coolant-out cryo valve heaters 

and neon lines while Linnehan installs the NCC power cable to the EPS test panel and 

reinstalls the MLI tent. They install the NCS Radiator conduit through the cryo vent insert 

opening in the aft bulkhead and engage the cryo vent insert latches and locking bolts. Then 

the NCS Radiator harnesses are mated to the NCS, the NCC saddle thermal cover opened 

and the CPL evaporator removed from the sock and tethered to the bulkhead standoff by 

Grunsfeld. Linnehan opens the NCS Radiator diode box, checks some LEDs and switches, 

and closes the diode box cover. He installs the CPL evaporator in the saddle, installs the 

saddle cover, engages its two bolts and closes the NCC saddle thermal cover. Together 

the astronauts close the aft shroud doors. 

The final closeout procedure follows the NCS installation. Grunsfeld inspects the FSS main 

umbilical mechanism and the P105/P106 covers, removes the LGA protective cover from 

the telescope and reinstalls it on the FSS, disengages the two center PIP pins on the BSP, 

retracts the mini-TA, retracts the port and starboard TAs, if required, to their landing 

configurations and takes a tool inventory. Meanwhile, Linnehan prepares the CATs 

installed on the MFR handrail for return into the airlock, egresses the MFR and performs 

the MFR stow procedure. That completes the fifth spacewalk. 

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EVA Timeline Overview 

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Experiments 

DTOs and DSOs 

Detailed Test Objectives (DTOs) are aimed at testing, evaluating or documenting space 

shuttle systems or hardware, or proposed improvements to space shuttle hardware, 

systems and operations. 

Detailed Supplementary Objectives (DSOs) are space and life science investigations. Their 

purpose is to determine the extent of physiological deconditioning resulting from space 

flight, to test countermeasures to those changes and to characterize the environment of the 

space shuttle relative to crew health. 

The following such experiments are aboard Columbia: 

DTO 700-14 

Single-String Global Positioning System 

The purpose of the Single-String Global Positioning System (GPS) is to demonstrate the 

performance and operation of the GPS during orbiter ascent, on-orbit, entry and landing 

phases. It uses a modified military GPS receiver processor and the existing orbiter GPS 

antennas. GPS data may be downlinked during all mission phases. This is the 21st flight of 

DTO 700-14. 

DTO 805 

Crosswind Landing Performance 

DTO 805 will demonstrate the capability to perform a manually controlled landing in the 

presence of a crosswind. The testing is done in two steps: 

1. Prelaunch: Ensure planning will allow selection of a runway with Microwave Scanning 

Beam Landing System support, which is a set of dual transmitters located beside the 

runway providing precision navigation vertically, horizontally and longitudinally with 

respect to the runway. This precision navigation subsystem helps provide a higher 

probability of a more precise landing with a crosswind of 10 to 15 knots as late in the 

flight as possible. 

2. Entry: This test requires that the crew perform a manually controlled landing in the 

presence of a 90-degree crosswind component of 10 to 15 knots steady state. During a 

crosswind landing, the drag chute will be deployed after nose gear touchdown when the 

vehicle is stable and tracking the runway centerline. This DTO has been manifested on 

68 previous flights. 

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DSO 490 

Bioavailability and Performance Effects of Promethazine During Space Flight 

Promethazine (PMZ) is the anti-motion sickness medication of choice for treating space 

motion sickness during shuttle missions. Usual side effects include dizziness, drowsiness, 

sedation and impaired psychomotor performance, which could impact crew performance of 

mission operations. Early reports from crewmembers indicate that these central nervous 

system side effects of PMZ are absent or greatly reduced in microgravity. Tests on 

Columbia will test PMZ’s performance, side effects, and efficacy in microgravity. On-orbit 

tests will evaluate responses to various doses and effectiveness of intramuscular, oral and 

suppository methods of administration. Results will then be compared with preflight 

evaluations. This is the second flight of DSO 490. 

DSO 493 

Monitoring Latent Virus Reactivation and Shedding in Astronauts 

The premise of this DSO is that the incidence and duration of latent virus reactivation in 

saliva and urine can increase during space flight. The objective is to determine the 

frequency of reactivation of latent viruses, latent virus shedding and clinical disease after 

exposure to the physical, physiological and psychological stressors associated with space 

flight. Induced-induced alterations in the immune response become increasingly important 

on long missions, particularly the potential for reactivation and dissemination (shedding) of 

latent viruses. An example of a latent virus is Herpes Simplex Type 1 (HSV-1), which 

infects 70 to 80 percent of all adults. Its classic manifestations are cold sores, pharyngitis 

and tonsillitis. It usually is acquired through contact with the saliva, skin or mucous 

membranes of an infected individual. However, many recurrences are asymptomatic, 

resulting in shedding of the virus. 

DSO 496 

Individual Susceptibility to Post-Space Flight Orthostatic Intolerance 

Susceptibility to postflight orthostatic intolerancelightheadedness or fainting upon return 

to Earthis highly individual. Some astronauts are little affected, while others have severe 

symptoms. Women are more often affected than men. This DSO will study the mechanisms 

responsible for these differences to customize countermeasure protocols. It has been well 

documented that space flight significantly alters cardiovascular function. One of the most 

important changes from a crew safety standpoint is postflight loss of orthostatic tolerance, 

which causes astronauts to have difficulty walking independently and induces 

lightheadedness or fainting. These effects may impair their ability to leave the orbiter after it 

lands. This DSO will study preflight and postflight differences in susceptible and 

nonsusceptible astronauts. There are no on-orbit activities associated with this DSO. 

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DSO 498 

Space Flight and Immune Function 

Astronauts face an increasing risk of contracting infectious diseases as they work and live 

for longer periods in the crowded conditions and closed environments of spacecraft such as 

the International Space Station. The effects of space flight on the human immune system, 

which plays a pivotal role in warding off infections, is not fully understood. Understanding 

the changes in immune functions caused by exposure to microgravity will allow researchers 

to develop countermeasures to minimize the risk of infection. DSO 498 will look at the 

effects of space flight on neutrophils, monocytes and cytotoxic cells, which play an 

important role in maintaining an effective defense against infectious agents. Scientists 

believe that space changes the way these cells function. Researchers will analyze 

neutrophils and monocytes from astronaut blood samples taken before and after the flight. 

They will also assess the subjects’ pre- and postflight production of cytotoxic cells and 

cytokine. This study will complement previous and continuing immunology studies of 

astronauts’ adaptation to space. 

DSO 500 

Induced-Induced Reactivation of Latent Epstein-Barr Virus 

The effects of microgravity, along with associated physical and psychological stress, 

decrease Epstein-Barr virus (EBV)-specific T-cell immunity and reactivate latent EBV in 

infected B-lymphocytes. DSO 500 will examine the mechanisms of induced-induced 

alterations in human immune function and latent virus reactivation. Specifically, it will 

determine the magnitude of immunosuppression as a result of space flight by analyzing 

stress hormones, performing quantitative analysis of EBV replication using molecular and 

serological methods, and determining virus-specific T-cell immune function. This is the 

second flight of DSO 500. 

DSO 503S 

Test of Midodrine as a Countermeasure Against Postflight Orthostatic 

Hypotension 

After space flight, astronauts returning to upright posture may experience the inability to 

maintain adequate arterial pressure and cerebral perfusion (orthostatic or postural 

hypotension). This may result in lightheadedness or loss of consciousness during reentry or 

egress. DSO 503S will evaluate the efficacy of midodrine, a medicine commonly used to 

treat low blood pressure. It works by stimulating nerve endings in blood vessels, causing 

the blood vessels to tighten, which increases blood pressure. The experiment will assess 

midodrine’s effectiveness in reducing the incidence and/or severity of orthostatic 

hypotension in returning astronauts. This is the second flight of DSO 503S. 

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DSO 634 

Sleep–Wake Actigraphy and Light Exposure During Space Flight 

Disruption of sleep during space flight, both short and long duration, is associated with 

inappropriately timed (non-24 hour) or insufficiently intense light exposure. Sleep disruption 

and circadian misalignment can lead to unsatisfactory sleep quality and daytime alertness, 

which could impair mission success. This experiment will monitor sleep–wake activity and 

light exposure patterns obtained in flight. These data should help better understand the 

effects of space flight on sleep, as well as aid in the development of effective 

countermeasures for both short- and long-duration space flight. 

DSO 635 

Spatial Reorientation Following Space Flight 

Spatial orientation is altered during and after space flight by a shift of central vestibular 

processing (from a gravitational frame of reference to an internal, head-centered frame of 

reference) that occurs during adaptation to microgravity and is reversed during the first few 

days after return to Earth. During the postflight re-adaptive period, discordant sensory 

stimuli can temporarily disorient a subject by triggering a shift (state change) to the 

previously learned, internally referenced, microgravity-adapted pattern of spatial orientation 

and sensorimotor control. This DSO will examine both the adaptive changes in the spatial 

reference frame used for coding spatial orientation and sensorimotor control, as well as the 

fragility of the adaptive process and the feasibility of driving state changes in central 

vestibular processing via discordant sensory stimuli using balance control tests and eye 

movement responses to pitch-axis rotation in a short-arm centrifuge. The findings are 

expected to demonstrate the degree to which challenging motion environments may affect 

postflight re-adaptation and lead to a better understanding of safe postflight activity 

regimens. 

DSO 802 

Educational Activities 

This DSO will provide live TV downlink of the mission to classrooms in hopes of attracting 

students to careers in science, engineering and mathematics. The addition of this DSO to a 

particular flight is coordinated through the JSC Educational Working Group. The tasks 

required by this DSO support three distinct objectives: 1) Produce educational products, 

such as 20-minute video lessons, with scenes of educational activities performed by the 

flight crew recorded both in space and on the ground. 2) Support the live TV downlink of 

educational activities performed by the flight crew explicitly for, or involving participation by, 

students and teachers. 3) Support the live or videotaped TV downlink of educational 

activities performed by the flight crew for a general audience. 

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Shuttle Reference Data 

Shuttle Abort History 

RSLS Abort History:

(STS-41 D) June 26, 1984

The countdown for the second launch attempt for Discovery’s maiden flight ended at T4 seconds when the orbiter’s computers detected a sluggish valve in main engine #3. 

The main engine was replaced and Discovery was finally launched on August 30, 1984. 

(STS-51 F) July 12, 1985

The countdown for Challenger’s launch was halted at T-3 seconds when on-board 

computers detected a problem with a coolant valve on main engine #2. The valve was 

replaced and Challenger was launched on July 29, 1985. 

(STS-55) March 22, 1993

The countdown for Columbia’s launch was halted by on-board computers at T-3 

seconds following a problem with purge pressure readings in the oxidizer preburner on 

main engine #2 Columbia’s three main engines were replaced on the launch pad, and 

the flight was rescheduled behind Discovery’s launch on STS-56. Columbia finally 

launched on April 26, 1993. 

(STS-51) August 12, 1993

The countdown for Discovery’s third launch attempt ended at the T-3 second mark 

when on-board computers detected the failure of one of four sensors in main engine #2 

which monitor the flow of hydrogen fuel to the engine. All of Discovery’s main engines 

were ordered replaced on the launch pad, delaying the Shuttle’s fourth launch attempt 

until September 12, 1993. 

(STS-68) August 18, 1994

The countdown for Endeavour’s first launch attempt ended 1.9 seconds before liftoff 

when on-board computers detected higher than acceptable readings in one channel of a 

sensor monitoring the discharge temperature of the high pressure oxidizer turbopump in 

main engine #3. A test firing of the engine at the Stennis Space Center in Mississippi on 

September 2nd confirmed that a slight drift in a fuel flow meter in the engine caused a 

slight increase in the turbopump’s temperature. The test firing also confirmed a slightly 

slower start for main engine #3 during the pad abort, which could have contributed to 

the higher temperatures. After Endeavour was brought back to the Vehicle Assembly 

Building to be outfitted with three replacement engines, NASA managers set October 

2nd as the date for Endeavour’s second launch attempt. 

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Abort to Orbit History:

(STS-51 F) July 29, 1985

After an RSLS abort on July 12, 1985, Challenger was launched on July 29, 1985. Five 

minutes and 45 seconds after launch, a sensor problem resulted in the shutdown of 

center engine #1, resulting in a safe "abort to orbit" and successful completion of the 

mission.

Updated: 05/22/2001 

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Shuttle Reference Data 

Shuttle Abort Modes 

RSLS ABORTS 

These occur when the onboard shuttle computers detect a problem and command a halt in 

the launch sequence after taking over from the Ground Launch Sequencer and before Solid 

Rocket Booster ignition. 

ASCENT ABORTS 

Selection of an ascent abort mode may become necessary if there is a failure that affects 

vehicle performance, such as the failure of a space shuttle main engine or an orbital 

maneuvering system. Other failures requiring early termination of a flight, such as a cabin 

leak, might also require the selection of an abort mode. 

There are two basic types of ascent abort modes for space shuttle missions: intact aborts 

and contingency aborts. Intact aborts are designed to provide a safe return of the orbiter to 

a planned landing site. Contingency aborts are designed to permit flight crew survival 

following more severe failures when an intact abort is not possible. A contingency abort 

would generally result in a ditch operation. 

INTACT ABORTS 

There are four types of intact aborts: abort to orbit (ATO), abort once around (AOA), 

transoceanic abort landing (TAL) and return to launch site (RTLS). 

Return to Launch Site 

The RTLS abort mode is designed to allow the return of the orbiter, crew, and payload to 

the launch site, Kennedy Space Center, approximately 25 minutes after lift-off. 

The RTLS profile is designed to accommodate the loss of thrust from one space shuttle 

main engine between lift-off and approximately four minutes 20 seconds, at which time not 

enough main propulsion system propellant remains to return to the launch site. 

An RTLS can be considered to consist of three stages--a powered stage, during which the 

space shuttle main engines are still thrusting; an ET separation phase; and the glide phase, 

during which the orbiter glides to a landing at the Kennedy Space Center. The powered 

RTLS phase begins with the crew selection of the RTLS abort, which is done after solid 

rocket booster separation. The crew selects the abort mode by positioning the abort rotary 

switch to RTLS and depressing the abort push button. The time at which the RTLS is 

selected depends on the reason for the abort. For example, a three-engine RTLS is 

selected at the last moment, approximately three minutes 34 seconds into the mission; 

whereas an RTLS chosen due to an engine out at lift-off is selected at the earliest time, 

approximately two minutes 20 seconds into the mission (after solid rocket booster 

separation). 

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After RTLS is selected, the vehicle continues downrange to dissipate excess main 

propulsion system propellant. The goal is to leave only enough main propulsion system 

propellant to be able to turn the vehicle around, fly back towards the Kennedy Space 

Center and achieve the proper main engine cutoff conditions so the vehicle can glide to the 

Kennedy Space Center after external tank separation. During the downrange phase, a 

pitch-around maneuver is initiated (the time depends in part on the time of a space shuttle 

main engine failure) to orient the orbiter/external tank configuration to a heads up attitude, 

pointing toward the launch site. At this time, the vehicle is still moving away from the launch 

site, but the space shuttle main engines are now thrusting to null the downrange velocity. In 

addition, excess orbital maneuvering system and reaction control system propellants are 

dumped by continuous orbital maneuvering system and reaction control system engine 

thrustings to improve the orbiter weight and center of gravity for the glide phase and 

landing. 

The vehicle will reach the desired main engine cutoff point with less than 2 percent excess 

propellant remaining in the external tank. At main engine cutoff minus 20 seconds, a pitchdown maneuver (called powered pitch-down) takes the mated vehicle to the required 

external tank separation attitude and pitch rate. After main engine cutoff has been 

commanded, the external tank separation sequence begins, including a reaction control 

system translation that ensures that the orbiter does not recontact the external tank and 

that the orbiter has achieved the necessary pitch attitude to begin the glide phase of the 

RTLS. 

After the reaction control system translation maneuver has been completed, the glide 

phase of the RTLS begins. From then on, the RTLS is handled similarly to a normal entry. 

Transoceanic Abort Landing 

The TAL abort mode was developed to improve the options available when a space shuttle 

main engine fails after the last RTLS opportunity but before the first time that an AOA can 

be accomplished with only two space shuttle main engines or when a major orbiter system 

failure, for example, a large cabin pressure leak or cooling system failure, occurs after the 

last RTLS opportunity, making it imperative to land as quickly as possible. 

In a TAL abort, the vehicle continues on a ballistic trajectory across the Atlantic Ocean to 

land at a predetermined runway. Landing occurs approximately 45 minutes after launch. 

The landing site is selected near the nominal ascent ground track of the orbiter in order to 

make the most efficient use of space shuttle main engine propellant. The landing site also 

must have the necessary runway length, weather conditions and U.S. State Department 

approval. Currently, the three landing sites that have been identified for a due east launch 

are Moron, Spain; Dakar, Senegal; and Ben Guerur, Morocco (on the west coast of Africa). 

To select the TAL abort mode, the crew must place the abort rotary switch in the TAL/AOA 

position and depress the abort push button before main engine cutoff. (Depressing it after 

main engine cutoff selects the AOA abort mode.) The TAL abort mode begins sending 

commands to steer the vehicle toward the plane of the landing site. It also rolls the vehicle 

heads up before main engine cutoff and sends commands to begin an orbital maneuvering 

system propellant dump (by burning the propellants through the orbital maneuvering 

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system engines and the reaction control system engines). This dump is necessary to 

increase vehicle performance (by decreasing weight), to place the center of gravity in the 

proper place for vehicle control, and to decrease the vehicle's landing weight. 

TAL is handled like a nominal entry. 

Abort to Orbit 

An ATO is an abort mode used to boost the orbiter to a safe orbital altitude when 

performance has been lost and it is impossible to reach the planned orbital altitude. If a 

space shuttle main engine fails in a region that results in a main engine cutoff under speed, 

the Mission Control Center will determine that an abort mode is necessary and will inform 

the crew. The orbital maneuvering system engines would be used to place the orbiter in a 

circular orbit. 

Abort Once Around 

The AOA abort mode is used in cases in which vehicle performance has been lost to such 

an extent that either it is impossible to achieve a viable orbit or not enough orbital 

maneuvering system propellant is available to accomplish the orbital maneuvering system 

thrusting maneuver to place the orbiter on orbit and the deorbit thrusting maneuver. In 

addition, an AOA is used in cases in which a major systems problem (cabin leak, loss of 

cooling) makes it necessary to land quickly. In the AOA abort mode, one orbital 

maneuvering system thrusting sequence is made to adjust the post-main engine cutoff orbit 

so a second orbital maneuvering system thrusting sequence will result in the vehicle 

deorbiting and landing at the AOA landing site (White Sands, N.M.; Edwards Air Force 

Base; or the Kennedy Space Center). Thus, an AOA results in the orbiter circling the Earth 

once and landing approximately 90 minutes after lift-off. 

After the deorbit thrusting sequence has been executed, the flight crew flies to a landing at 

the planned site much as it would for a nominal entry. 

CONTINGENCY ABORTS 

Contingency aborts are caused by loss of more than one main engine or failures in other 

systems. Loss of one main engine while another is stuck at a low thrust setting may also 

necessitate a contingency abort. Such an abort would maintain orbiter integrity for in-flight 

crew escape if a landing cannot be achieved at a suitable landing field. 

Contingency aborts due to system failures other than those involving the main engines 

would normally result in an intact recovery of vehicle and crew. Loss of more than one main 

engine may, depending on engine failure times, result in a safe runway landing. However, 

in most three-engine-out cases during ascent, the orbiter would have to be ditched. The inflight crew escape system would be used before ditching the orbiter. 

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ABORT DECISIONS 

There is a definite order of preference for the various abort modes. The type of failure and 

the time of the failure determine which type of abort is selected. In cases where 

performance loss is the only factor, the preferred modes would be ATO, AOA, TAL and 

RTLS, in that order. The mode chosen is the highest one that can be completed with the 

remaining vehicle performance. 

In the case of some support system failures, such as cabin leaks or vehicle cooling 

problems, the preferred mode might be the one that will end the mission most quickly. In 

these cases, TAL or RTLS might be preferable to AOA or ATO. A contingency abort is 

never chosen if another abort option exists. 

The Mission Control Center-Houston is prime for calling these aborts because it has a more 

precise knowledge of the orbiter's position than the crew can obtain from onboard systems. 

Before main engine cutoff, Mission Control makes periodic calls to the crew to tell them 

which abort mode is (or is not) available. If ground communications are lost, the flight crew 

has onboard methods, such as cue cards, dedicated displays and display information, to 

determine the current abort region. 

Which abort mode is selected depends on the cause and timing of the failure causing the 

abort and which mode is safest or improves mission success. If the problem is a space 

shuttle main engine failure, the flight crew and Mission Control Center select the best 

option available at the time a space shuttle main engine fails. 

If the problem is a system failure that jeopardizes the vehicle, the fastest abort mode that 

results in the earliest vehicle landing is chosen. RTLS and TAL are the quickest options (35 

minutes), whereas an AOA requires approximately 90 minutes. Which of these is selected 

depends on the time of the failure with three good space shuttle main engines. 

The flight crew selects the abort mode by positioning an abort mode switch and depressing 

an abort push button. 

Updated: 05/22/2001 

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Shuttle Reference Data 

Space Shuttle Rendezvous Maneuvers 

COMMON SHUTTLE RENDEZVOUS MANEUVERS

OMS-1 (Orbit insertion) - Rarely used ascent abort burn 

OMS-2 (Orbit insertion) - Typically used to circularize the initial orbit following ascent, 

completing orbital insertion. For ground-up rendezvous flights, also considered a 

rendezvous phasing burn 

NC (Rendezvous phasing) - Performed to hit a range relative to the target at a future 

time 

NH (Rendezvous height adjust) - Performed to hit a delta-height relative to the target 

at a future time 

NPC (Rendezvous plane change) - Performed to remove planar errors relative to the 

target at a future time 

NCC (Rendezvous corrective combination) - First on-board targeted burn in the 

rendezvous sequence. Using star tracker data, it is performed to remove phasing and 

height errors relative to the target at Ti 

Ti (Rendezvous terminal intercept) - Second on-board targeted burn in the 

rendezvous sequence. Using primarily rendezvous radar data, it places the Orbiter on a 

trajectory to intercept the target in one orbit 

MC-1, MC-2, MC-3, MC-4 (Rendezvous midcourse burns) - These on-board targeted 

burns use star tracker and rendezvous radar data to correct the post-Ti trajectory in 

preparation for the final, manual proximity operations phase 

Updated: 05/22/2001 

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Shuttle Reference Data 

Space Shuttle Solid Rocket Boosters 

The two SRBs provide the main thrust to lift the space shuttle off the pad and up to an 

altitude of about 150,000 feet, or 24 nautical miles (28 statute miles). In addition, the two 

SRBs carry the entire weight of the external tank and orbiter and transmit the weight load 

through their structure to the mobile launcher platform. 

Each booster has a thrust (sea level) of approximately 3,300,000 pounds at launch. They 

are ignited after the three space shuttle main engines' thrust level is verified. The two SRBs 

provide 71.4 percent of the thrust at lift- off and during first-stage ascent. Seventy- five 

seconds after SRB separation, SRB apogee occurs at an altitude of approximately 220,000 

feet, or 35 nautical miles (40 statute miles). SRB impact occurs in the ocean approximately 

122 nautical miles (140 statute miles) downrange. 

The SRBs are the largest solid-propellant motors ever flown and the first designed for 

reuse. Each is 149.16 feet long and 12.17 feet in diameter. 

Each SRB weighs approximately 1,300,000 pounds at launch. The propellant for each solid 

rocket motor weighs approximately 1,100,000 pounds. The inert weight of each SRB is 

approximately 192,000 pounds. 

Primary elements of each booster are the motor (including case, propellant, igniter and 

nozzle), structure, separation systems, operational flight instrumentation, recovery avionics, 

pyrotechnics, deceleration system, thrust vector control system and range safety destruct 

system. 

Each booster is attached to the external tank at the SRB’s aft frame by two lateral sway 

braces and a diagonal attachment. The forward end of each SRB is attached to the 

external tank at the forward end of the SRB’s forward skirt. On the launch pad, each 

booster also is attached to the mobile launcher platform at the aft skirt by four bolts and 

nuts that are severed by small explosives at lift-off. 

During the downtime following the Challenger accident, detailed structural analyses were 

performed on critical structural elements of the SRB. Analyses were primarily focused in 

areas where anomalies had been noted during postflight inspection of recovered hardware. 

One of the areas was the attach ring where the SRBs are connected to the external tank. 

Areas of distress were noted in some of the fasteners where the ring attaches to the SRB 

motor case. This situation was attributed to the high loads encountered during water 

impact. To correct the situation and ensure higher strength margins during ascent, the 

attach ring was redesigned to encircle the motor case completely (360 degrees). 

Previously, the attach ring formed a C and encircled the motor case 270 degrees. 

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Additionally, special structural tests were performed on the aft skirt. During this test 

program, an anomaly occurred in a critical weld between the hold-down post and skin of 

the skirt. A redesign was implemented to add reinforcement brackets and fittings in the aft 

ring of the skirt. 

These two modifications added approximately 450 pounds to the weight of each SRB. 

The propellant mixture in each SRB motor consists of an ammonium perchlorate (oxidizer, 

69.6 percent by weight), aluminum (fuel, 16 percent), iron oxide (a catalyst, 0.4 percent), a 

polymer (a binder that holds the mixture together, 12.04 percent), and an epoxy curing 

agent (1.96 percent). The propellant is an 11-point star-shaped perforation in the forward 

motor segment and a double-truncated-cone perforation in each of the aft segments and aft 

closure. This configuration provides high thrust at ignition and then reduces the thrust by 

approximately a third 50 seconds after lift-off to prevent overstressing the vehicle during 

maximum dynamic pressure. 

The SRBs are used as matched pairs and each is made up of four solid rocket motor 

segments. The pairs are matched by loading each of the four motor segments in pairs from 

the same batches of propellant ingredients to minimize any thrust imbalance. The 

segmented-casing design assures maximum flexibility in fabrication and ease of 

transportation and handling. Each segment is shipped to the launch site on a heavy-duty 

rail car with a specially built cover. 

The nozzle expansion ratio of each booster beginning with the STS-8 mission is 7-to-79. 

The nozzle is gimbaled for thrust vector (direction) control. Each SRB has its own 

redundant auxiliary power units and hydraulic pumps. The all-axis gimbaling capability is 8 

degrees. Each nozzle has a carbon cloth liner that erodes and chars during firing. The 

nozzle is a convergent-divergent, movable design in which an aft pivot-point flexible 

bearing is the gimbal mechanism. 

The cone- shaped aft skirt reacts the aft loads between the SRB and the mobile launcher 

platform. The four aft separation motors are mounted on the skirt. The aft section contains 

avionics, a thrust vector control system that consists of two auxiliary power units and 

hydraulic pumps, hydraulic systems and a nozzle extension jettison system. 

The forward section of each booster contains avionics, a sequencer, forward separation 

motors, a nose cone separation system, drogue and main parachutes, a recovery beacon, 

a recovery light, a parachute camera on selected flights and a range safety system. 

Each SRB has two integrated electronic assemblies, one forward and one aft. After 

burnout, the forward assembly initiates the release of the nose cap and frustum and turns 

on the recovery aids. The aft assembly, mounted in the external tank/SRB attach ring, 

connects with the forward assembly and the orbiter avionics systems for SRB ignition 

commands and nozzle thrust vector control. Each integrated electronic assembly has a 

multiplexer/ demultiplexer, which sends or receives more than one message, signal or unit 

of information on a single communication channel. 

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Eight booster separation motors (four in the nose frustum and four in the aft skirt) of each 

SRB thrust for 1.02 seconds at SRB separation from the external tank. Each solid rocket 

separation motor is 31.1 inches long and 12.8 inches in diameter. 

Location aids are provided for each SRB, frustum/drogue chutes and main parachutes. 

These include a transmitter, antenna, strobe/converter, battery and salt water switch 

electronics. The location aids are designed for a minimum operating life of 72 hours and 

when refurbished are considered usable up to 20 times. The flashing light is an exception. 

It has an operating life of 280 hours. The battery is used only once. 

The SRB nose caps and nozzle extensions are not recovered. 

The recovery crew retrieves the SRBs, frustum/drogue chutes, and main parachutes. The 

nozzles are plugged, the solid rocket motors are dewatered, and the SRBs are towed back 

to the launch site. Each booster is removed from the water, and its components are 

disassembled and washed with fresh and deionized water to limit salt water corrosion. The 

motor segments, igniter and nozzle are shipped back to Thiokol for refurbishment. 

Each SRB incorporates a range safety system that includes a battery power source, 

receiver/ decoder, antennas and ordnance. 

HOLD-DOWN POSTS 

Each solid rocket booster has four hold-down posts that fit into corresponding support posts 

on the mobile launcher platform. Hold-down bolts hold the SRB and launcher platform 

posts together. Each bolt has a nut at each end, but only the top nut is frangible. The top 

nut contains two NASA standard detonators, which are ignited at solid rocket motor ignition 

commands. 

When the two NSDs are ignited at each hold-down, the hold-down bolt travels downward 

because of the release of tension in the bolt (pretensioned before launch), NSD gas 

pressure and gravity. The bolt is stopped by the stud deceleration stand, which contains 

sand. The SRB bolt is 28 inches long and is 3.5 inches in diameter. The frangible nut is 

captured in a blast container. 

The solid rocket motor ignition commands are issued by the orbiter''s computers through 

the master events controllers to the hold-down pyrotechnic initiator controllers on the 

mobile launcher platform. They provide the ignition to the hold-down NSDs. The launch 

processing system monitors the SRB hold-down PICs for low voltage during the last 16 

seconds before launch. PIC low voltage will initiate a launch hold. 

SRB IGNITION 

SRB ignition can occur only when a manual lock pin from each SRB safe and arm device 

has been removed. The ground crew removes the pin during prelaunch activities. At T 

minus five minutes, the SRB safe and arm device is rotated to the arm position. The solid 

rocket motor ignition commands are issued when the three SSMEs are at or above 90-

percent rated thrust, no SSME fail and/or SRB ignition PIC low voltage is indicated and 

there are no holds from the LPS. 

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The solid rocket motor ignition commands are sent by the orbiter computers through the 

MECs to the safe and arm device NSDs in each SRB. A PIC single-channel capacitor 

discharge device controls the firing of each pyrotechnic device. Three signals must be 

present simultaneously for the PIC to generate the pyro firing output. These signals--arm, 

fire 1 and fire 2--originate in the orbiter general-purpose computers and are transmitted to 

the MECs. The MECs reformat them to 28-volt dc signals for the PICs. The arm signal 

charges the PIC capacitor to 40 volts dc (minimum of 20 volts dc). 

The fire 2 commands cause the redundant NSDs to fire through a thin barrier seal down a 

flame tunnel. This ignites a pyro booster charge, which is retained in the safe and arm device 

behind a perforated plate. The booster charge ignites the propellant in the igniter initiator; 

and combustion products of this propellant ignite the solid rocket motor initiator, which fires 

down the length of the solid rocket motor igniting the solid rocket motor propellant. 

The GPC launch sequence also controls certain critical main propulsion system valves and 

monitors the engine-ready indications from the SSMEs. The MPS start commands are 

issued by the onboard computers at T minus 6.6 seconds (staggered start--engine three, 

engine two, engine one--all approximately within 0.25 of a second), and the sequence 

monitors the thrust buildup of each engine. All three SSMEs must reach the required 90-

percent thrust within three seconds; otherwise, an orderly shutdown is commanded and 

safing functions are initiated. 

Normal thrust buildup to the required 90-percent thrust level will result in the SSMEs being 

commanded to the lift-off position at T minus three seconds as well as the fire 1 command 

being issued to arm the SRBs. At T minus three seconds, the vehicle base bending load 

modes are allowed to initialize (movement of approximately 25.5 inches measured at the tip 

of the external tank, with movement towards the external tank). 

At T minus zero, the two SRBs are ignited, under command of the four onboard computers; 

separation of the four explosive bolts on each SRB is initiated (each bolt is 28 inches long 

and 3.5 inches in diameter); the two T-0 umbilicals (one on each side of the spacecraft) are 

retracted; the onboard master timing unit, event timer and mission event timers are started; 

the three SSMEs are at 100 percent; and the ground launch sequence is terminated. 

The solid rocket motor thrust profile is tailored to reduce thrust during the maximum 

dynamic pressure region. 

ELECTRICAL POWER DISTRIBUTION 

Electrical power distribution in each SRB consists of orbiter-supplied main dc bus power to 

each SRB via SRB buses A, B and C. Orbiter main dc buses A, B and C supply main dc 

bus power to corresponding SRB buses A, B and C. In addition, orbiter main dc bus C 

supplies backup power to SRB buses A and B, and orbiter bus B supplies backup power to 

SRB bus C. This electrical power distribution arrangement allows all SRB buses to remain 

powered in the event one orbiter main bus fails. 

The nominal dc voltage is 28 volts dc, with an upper limit of 32 volts dc and a lower limit of 

24 volts dc. 

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HYDRAULIC POWER UNITS 

There are two self-contained, independent HPUs on each SRB. Each HPU consists of an 

auxiliary power unit, fuel supply module, hydraulic pump, hydraulic reservoir and hydraulic 

fluid manifold assembly. The APUs are fueled by hydrazine and generate mechanical shaft 

power to a hydraulic pump that produces hydraulic pressure for the SRB hydraulic system. 

The two separate HPUs and two hydraulic systems are located on the aft end of each SRB 

between the SRB nozzle and aft skirt. The HPU components are mounted on the aft skirt 

between the rock and tilt actuators. The two systems operate from T minus 28 seconds 

until SRB separation from the orbiter and external tank. The two independent hydraulic 

systems are connected to the rock and tilt servoactuators. 

The APU controller electronics are located in the SRB aft integrated electronic assemblies 

on the aft external tank attach rings. 

The APUs and their fuel systems are isolated from each other. Each fuel supply module 

(tank) contains 22 pounds of hydrazine. The fuel tank is pressurized with gaseous nitrogen 

at 400 psi, which provides the force to expel (positive expulsion) the fuel from the tank to 

the fuel distribution line, maintaining a positive fuel supply to the APU throughout its 

operation. 

The fuel isolation valve is opened at APU startup to allow fuel to flow to the APU fuel pump 

and control valves and then to the gas generator. The gas generator's catalytic action 

decomposes the fuel and creates a hot gas. It feeds the hot gas exhaust product to the 

APU two-stage gas turbine. Fuel flows primarily through the startup bypass line until the 

APU speed is such that the fuel pump outlet pressure is greater than the bypass line's. 

Then all the fuel is supplied to the fuel pump. 

The APU turbine assembly provides mechanical power to the APU gearbox. The gearbox 

drives the APU fuel pump, hydraulic pump and lube oil pump. The APU lube oil pump 

lubricates the gearbox. The turbine exhaust of each APU flows over the exterior of the gas 

generator, cooling it, and is then directed overboard through an exhaust duct. 

When the APU speed reaches 100 percent, the APU primary control valve closes, and the 

APU speed is controlled by the APU controller electronics. If the primary control valve logic 

fails to the open state, the secondary control valve assumes control of the APU at 112-

percent speed. 

Each HPU on an SRB is connected to both servoactuators on that SRB. One HPU serves 

as the primary hydraulic source for the servoactuator, and the other HPU serves as the 

secondary hydraulics for the servoactuator. Each sevoactuator has a switching valve that 

allows the secondary hydraulics to power the actuator if the primary hydraulic pressure 

drops below 2,050 psi. A switch contact on the switching valve will close when the valve is 

in the secondary position. When the valve is closed, a signal is sent to the APU controller 

that inhibits the 100-percent APU speed control logic and enables the 112-percent APU 

speed control logic. The 100-percent APU speed enables one APU/HPU to supply 

sufficient operating hydraulic pressure to both servoactuators of that SRB. 

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The APU 100-percent speed corresponds to 72,000 rpm, 110-percent to 79,200 rpm, and 

112-percent to 80,640 rpm. 

The hydraulic pump speed is 3,600 rpm and supplies hydraulic pressure of 3,050, plus or 

minus 50, psi. A high-pressure relief valve provides overpressure protection to the hydraulic 

system and relieves at 3,750 psi. 

The APUs/HPUs and hydraulic systems are reusable for 20 missions. 

THRUST VECTOR CONTROL 

Each SRB has two hydraulic gimbal servoactuators: one for rock and one for tilt. The 

servoactuators provide the force and control to gimbal the nozzle for thrust vector control. 

The space shuttle ascent thrust vector control portion of the flight control system directs the 

thrust of the three shuttle main engines and the two SRB nozzles to control shuttle attitude 

and trajectory during lift-off and ascent. Commands from the guidance system are 

transmitted to the ATVC drivers, which transmit signals proportional to the commands to 

each servoactuator of the main engines and SRBs. Four independent flight control system 

channels and four ATVC channels control six main engine and four SRB ATVC drivers, 

with each driver controlling one hydraulic port on each main and SRB servoactuator. 

Each SRB servoactuator consists of four independent, two-stage servovalves that receive 

signals from the drivers. Each servovalve controls one power spool in each actuator, which 

positions an actuator ram and the nozzle to control the direction of thrust. 

The four servovalves in each actuator provide a force-summed majority voting arrangement 

to position the power spool. With four identical commands to the four servovalves, the 

actuator force-sum action prevents a single erroneous command from affecting power ram 

motion. If the erroneous command persists for more than a predetermined time, differential 

pressure sensing activates a selector valve to isolate and remove the defective servovalve 

hydraulic pressure, permitting the remaining channels and servovalves to control the 

actuator ram spool. 

Failure monitors are provided for each channel to indicate which channel has been 

bypassed. An isolation valve on each channel provides the capability of resetting a failed or 

bypassed channel. 

Each actuator ram is equipped with transducers for position feedback to the thrust vector 

control system. Within each servoactuator ram is a splashdown load relief assembly to 

cushion the nozzle at water splashdown and prevent damage to the nozzle flexible bearing. 

SRB RATE GYRO ASSEMBLIES 

Each SRB contains two RGAs, with each RGA containing one pitch and one yaw gyro. 

These provide an output proportional to angular rates about the pitch and yaw axes to the 

orbiter computers and guidance, navigation and control system during first-stage ascent 

flight in conjunction with the orbiter roll rate gyros until SRB separation. At SRB separation, 

a switchover is made from the SRB RGAs to the orbiter RGAs. 

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The SRB RGA rates pass through the orbiter flight aft multiplexers/ demultiplexers to the 

orbiter GPCs. The RGA rates are then mid-value- selected in redundancy management to 

provide SRB pitch and yaw rates to the user software. The RGAs are designed for 20 

missions. 

SRB SEPARATION 

SRB separation is initiated when the three solid rocket motor chamber pressure 

transducers are processed in the redundancy management middle value select and the 

head-end chamber pressure of both SRBs is less than or equal to 50 psi. A backup cue is 

the time elapsed from booster ignition. 

The separation sequence is initiated, commanding the thrust vector control actuators to the 

null position and putting the main propulsion system into a second-stage configuration (0.8 

second from sequence initialization), which ensures the thrust of each SRB is less than 

100,000 pounds. Orbiter yaw attitude is held for four seconds, and SRB thrust drops to less 

than 60,000 pounds. 

The SRBs separate from the external tank within 30 milliseconds of the ordnance firing 

command. 

The forward attachment point consists of a ball (SRB) and socket (ET) held together by one 

bolt. The bolt contains one NSD pressure cartridge at each end. The forward attachment 

point also carries the range safety system cross-strap wiring connecting each SRB RSS 

and the ET RSS with each other. 

The aft attachment points consist of three separate struts: upper, diagonal and lower. Each 

strut contains one bolt with an NSD pressure cartridge at each end. The upper strut also 

carries the umbilical interface between its SRB and the external tank and on to the orbiter. 

There are four booster separation motors on each end of each SRB. The BSMs separate 

the SRBs from the external tank. The solid rocket motors in each cluster of four are ignited 

by firing redundant NSD pressure cartridges into redundant confined detonating fuse 

manifolds. 

The separation commands issued from the orbiter by the SRB separation sequence initiate 

the redundant NSD pressure cartridge in each bolt and ignite the BSMs to effect a clean 

separation. 

Updated: 05/22/2001

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Shuttle Reference Data 

Space Shuttle Super Light Weight Tank (SLWT) 

The super lightweight external tank (SLWT) made its first shuttle flight June 2, 1998, on 

mission STS-91. The SLWT is 7,500 pounds lighter than the standard external tank. The 

lighter weight tank will allow the shuttle to deliver International Space Station elements 

(such as the service module) into the proper orbit. 

The SLWT is the same size as the previous design. But the liquid hydrogen tank and the 

liquid oxygen tank are made of aluminum lithium, a lighter, stronger material than the metal 

alloy used for the shuttle's current tank. The tank's structural design has also been 

improved, making it 30% stronger and 5% less dense. 

The SLWT, like the standard tank, is manufactured at Michoud Assembly, near New 

Orleans, Louisiana, by Lockheed Martin. 

The 154-foot-long external tank is the largest single component of the space shuttle. It 

stands taller than a 15-story building and has a diameter of about 27 feet. The external tank 

holds over 530,000 gallons of liquid hydrogen and liquid oxygen in two separate tanks. The 

hydrogen (fuel) and liquid oxygen (oxidizer) are used as propellants for the shuttle's three 

main engines. 

Updated: 05/22/2001

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Acronyms and Abbreviations 

ACS Advanced Camera for Surveys 

APE Articulating PFR Extender 

ASIPE Axial Science Instrument Protective Enclosure 

ASLR Aft Shroud Latch Repair 

ATM Auxiliary Transport Module 

BAPS Berthing and Positioning System 

BSP Berthing and Positioning System (BAPS) Support Post 

CASH Cross Aft Shroud Harness 

CATs Crew Aids and Tools 

CCD Charge Coupled Device 

CITE Cargo Integrated Test Equipment 

COSTAR Corrective Optics Space Telescope Axial Replacement 

CPL Capillary Pump Loop 

CVL Cryo Vent Line 

DBA Diode Box Assembly 

DBC Diode Box Controller 

EPS Electrical Power Subsystem 

ESM Electronics Support Module 

FDA Failure Detection Annunciator 

FHST Fixed Head Star Tracker 

FOC Faint Object Camera 

FSS Flight Support System 

HST Hubble Space Telescope 

IVT Interface Verification Test 

LED Light Emitting Diode

LGA Low Gain Antenna 

LGAPC Low Gain Antenna Protective Cover 

LOPE Large Orbital Replacement Unit Protective Enclosure 

MFR Manipulator Foot Restraint 

MLI Multi-Layer Insulation 

MULE Multi-Use Lightweight Equipment 

NCC NICMOS Cryo-Cooler 

NCS NICMOS Cooling System 

NICMOS Near Infrared Camera and Multi-Object Spectrometer 

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PCS Pointing Control Subsystem 

PCU Power Control Unit 

PCU-R Power Control Unit-Replacement 

PDM Primary Deployment Mechanism 

PDU Power Distribution Unit 

PFR Portable Foot Restraint 

PI Payload Interrogator 

RAC Rigid Array Carrier 

RWA Reaction Wheel Assembly 

SAC Second Axial Carrier 

SADA Solar Array Drive Assembly 

SSV Space Shuttle Vehicle 

TI Transition Initiation 

VPF Vertical Processing Facility 

WFPC2 Wide Field and Planetary Camera 2 

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Media Assistance 

NASA Television Transmission 

NASA Television is available through the GE2 satellite system which is located on 

Transponder 9C, at 85 degrees west longitude, frequency 3880.0 MHz, audio 6.8 MHz. 

The schedule for television transmissions from the orbiter and for mission briefings will be 

available during the mission at Kennedy Space Center, Fla.; Marshall Space Flight Center, 

Huntsville, Ala.; Dryden Flight Research Center, Edwards, Calif.; Johnson Space Center, 

Houston, Texas; and NASA Headquarters, Washington, DC. The television schedule will be 

updated to reflect changes dictated by mission operations. 

Status Reports 

Status reports on countdown and mission progress, on-orbit activities and landing 

operations will be produced by the appropriate NASA news center. 

Briefings 

A mission press briefing schedule will be issued before launch. During the mission, status 

briefings by a flight director or mission operations representative and when appropriate, 

representatives from the payload team, will occur at least once each day. The updated 

NASA television schedule will indicate when mission briefings are planned. 

Internet Information 

Information is available through several sources on the Internet. The primary source for 

mission information is the NASA Human Space Flight Web, part of the World Wide Web. 

This site contains information on the crew and its mission and will be updated regularly with 

status reports, photos and video clips throughout the flight. The NASA Shuttle Web's 

address is: 

http://spaceflight.nasa.gov

General information on NASA and its programs is available through the NASA Home Page 

and the NASA Public Affairs Home Page: 

http://www.nasa.gov

or 

http://www.nasa.gov/newsinfo/index.html

Shuttle Pre-Launch Status Reports 

http://www-pao.ksc.nasa.gov/kscpao/status/stsstat/current.htm

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Information on other current NASA activities is available through the Today@NASA page: 

http://www.nasa.gov/today/index.html

The NASA TV schedule is available from the NTV Home Page: 

http://spaceflight.nasa.gov/realdata/nasatv/schedule.html

Resources for educators can be found at the following address: 

http://education.nasa.gov

Access by CompuServe 

Users with CompuServe accounts can access NASA press releases by typing "GO NASA" 

(no quotes) and making a selection from the categories offered. 

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Media Contacts 

Dwayne Brown 

NASA Headquarters 

Washington, DC 

Dwayne.brown@hq.nasa.gov

Space Shuttle/Space Station Policy 

202-358-1726 

Donald Savage 

NASA Headquarters 

Washington, DC 

Donald.savage@hq.nasa.gov

Space Science Policy, Budget 

202-358-1727 

Eileen Hawley 

Johnson Space Center 

Houston, TX 

Eileen.hawley1@jsc.nasa.gov

Astronauts/Mission Operations 

281-483-5111 

Nancy Neal 

Goddard Space Flight Center 

Greenbelt, MD 

Nancy.G.Neal1@gsfc.nasa.gov

Payload and Science Operations and Servicing 

301-286-0039 

Ray Villard 

Space Telescope Science Institute 

Baltimore, MD 

Hubble Science Program 

410-338-4514 

George Diller 

Kennedy Space Center 

Kennedy Space Center, Fla. 

George.Diller-1@ksc.nasa.gov

Space Shuttle Launch Operations 

321-867-2468 

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