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STS-61 PRESS KIT

FOR IMMEDIATE RELEASE
PUBLIC AFFAIRS CONTACTS

For Information on the Space Shuttle

Ed Campion    Policy/Management
  Headquarters, Wash., D.C.

James Hartsfield    Mission Operations/EVA
  Johnson Space Center,     Astronauts
  Houston

Bruce Buckingham    Launch Processing
  Kennedy Space Center, Fla.    KSC Landing Information

June Malone    External Tank/SRBs/SSMEs
  Marshall Space Flight
  Center, Huntsville, Ala.

Nancy Lovato    DFRF Landing Information
  Dryden Flight Research Facility,
  Edwards, Calif.

For Information on STS-61 Payloads

Sarah Keegan    HST Program/Science
  Headquarters, Wash., D.C.

Debra Rahn
  Headquarters, Wash., D.C.    HST International Elements

Jim Elliott    HST Project/Science
  Goddard Space Flight Center    STOCC Operations
  Greenbelt, Md.

Michael Finneran    HST Project/Science
  Goddard Space Flight Center    STOCC Operations
  Greenbelt, Md.

Bob MacMillin    Wide Field/Planetary Camera-II
  Jet Propulsion Laboratory
  Pasadena, Calif.

Jean Paul Paille    European Space Agency
  ESA, Hq., Paris

Ray Villard    HST Science, COSTAR
  Space Telescope Science Institute
  Baltimore, Md.

CONTENTS

GENERAL BACKGROUND MATERIAL

General Release    3
Media Services Information    4
Quick-Look Facts    5
Shuttle Abort Modes    7
Vechicle And Payload Weights  8
Summary Timeline    10
Orbital Events Summary    12

CARGO BAY PAYLOADS & ACTIVITIES

HST Servicing Mission-01 (HST/SM-01) Overview
             History of HST    14
             Mission Objectives And Success    ................15
             First Corrected Image Availability    15
              Science Accomplishments    16
             ESA Role in HST Program    17
     Servicing Mission Orbital Verification    17
     Key Hubble Scientific Goals Following the First Servicing Mission    19
      Hubble Space Telescope Rendezvous and Retrieval    19
     Commands to Hubble    20
     STS-61 Extravehicular Activities    20
     Replacement Hardware and Instruments    21
      Primary Servicing Tasks    25
      Secondary Servicing Tasks    35
     HST Tools and Crew Aids    35
Imax Camera     43

IN-CABIN PAYLOADS

Imax Camera    43
Air Force Maui Optical System (AMOS)    44
DTO-667 Pilot Inflight Landing Operations Trainer (PILOT)     44

STS-61 CREW BIOGRAPHIES

Richard O. Covey, Commander (CDR)    45
Kenneth D. Bowersox, Pilot (PLT)    45
Tom Akers, Mission Specialist 5 (MS5)    45
Jeffrey A. Hoffman, Mission Specialist 3 (MS3)    45
Kathryn C. Thornton,  Mission Specialist 1 (MS1)    46
Claude Nicollier, Mission Specialist 2 (MS2)    46
F. Story Musgrave, Mission Specialist 4 (MS4)    46

ACRONYMS AND ABBREVIATIONS    47


STS-61 General Release
FIVE SPACEWALKS TO SERVICE HUBBLE SPACE TELESCOPE HIGHLIGHTS
SHUTTLE MISSION STS-61

RELEASE:  93-204

     The December flight of Endeavour on Space Shuttle Mission STS-61 will see
the first in a series of planned visits to the orbiting Hubble Space Telescope
(HST).  The 11-day mission has been designed to accommodate a record five
spacewalks with the capability for an additional two if needed.

     The first HST servicing mission has three primary objectives: restoring
the planned scientific capabilities, restoring reliability of HST systems and
validating the HST on-orbit servicing concept.  These objectives will be
accomplished in a variety of tasks performed by the astronauts in Endeaour's
cargo bay.

     Replacement of the spacecraftUs solar arrays Q HSTUs source of electrical
power Q tops the primary servicing task list.  This is because solar array
jitter, or excessive flexing which happens when the telescope passes from cold
darkness into warm daylight, may be compromising the structural integrity of
the arrays.

     The objective to restore the HSTUs science capabilities will be
accomplished with the installation of the Wide Field/Planetary Camera-II and
the Corrective Optics Space Telescope Axial Replacement, both of which will
compensate for the spherical aberration of the primary mirror.

     The installation of new gyroscopes, which are required to point and track
HST, along with fuse plugs and electronic units will increase the reliability
of the HST system.

     Leading the seven-person STS-61 crew will be Mission Commander Dick Covey.
Pilot for the mission is Ken Bowersox. The mission specialists for the flight
are Kathy Thornton, Claude Nicollier, Jeff Hoffman, Story Musgrave and Tom
Akers. Working in pairs, Hoffman and Musgrave and Thorton and Akers, all of
whom have prevthe five spacewalks scheduled for flight days 4-8.

     Launch of Endeavour on the STS-61 mission is currently scheduled for no
earlier than Dec. 1, 1993 at 4:57 a.m.  EST. The planned mission duration is 10
days, 22 hours and 36 minutes.  An on-time launch on Dec. 1 would produce a
3:33 a.m.  EST landing on Dec. 12 at Kennedy Space Center's Shuttle Landing
Facility.

     STS-61 will be the 5th flight of Space Shuttle Endeavour and the 59th
flight of the Space Shuttle system.  The Hubble Space Telescope is an
international cooperative program between NASA and the European Space Agency.

- end-

STS-61 MEDIA SERVICES INFORMATION

NASA Select Television Transmission

     NASA Select television is available on Satcom F-2R, Transponder 13,
located at 72 degrees west longitude; frequency 3960.0 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.; Ames-Dryden Flight Research
Facility, Edwards, Calif.; Johnson Space Center, Houston and NASA Headquarters,
Washington, D.C. The television schedule will be updated to reflect changes
dictated by mission operations.

     Television schedules also may be obtained by calling COMSTOR 713/483-
5817.  COMSTOR is a computer data base service requiring the use of a telephone
modem.  A voice update of the television schedule is updated daily at noon
Eastern time.

Status Reports

     Status reports on countdown and mission progress, on-orbit activities and
landing operations will be produced by the appropriate NASA newscenter.

Briefings

     A mission press briefing schedule will be issued prior to launch.  During
the mission, status briefings by a Flight Director or Mission Operations
representative and when appropriate, representatives from the science team,
will occur at least once per day.  The updated NASA Select television schedule
will indicate when mission briefings are planned.


STS-61 QUICK LOOK

Launch Date/Site:    Dec. 1, 1993/Kennedy Space Center, Fla., Pad 39B
Launch Time:        4:57 a.m. EST (approximate)
Orbiter:            Endeavour (OV-105) 5th Flight
Orbit/Inclination:    320 nautical miles/28.45 degrees
Mission Duration:    10 days, 22 hours, 36 minutes (approximate)
Landing Time/Date:    3:33 a.m. EST (approximate)/Dec. 12, 1993
Primary Landing Site:    Kennedy Space Center, Fla.
Abort Landing Sites:    Return to Launch Site - KSC, Fla.
                TransAtlantic Abort Landing -
                    Banjul, The Gambia
                    Moron, Spain
                    Ben Guerir, Morocco
                Abort Once Around - Edwards AFB, Calif.

Crew: Dick Covey, Commander (CDR)
      Ken Bowersox, Pilot (PLT)
      Kathy Thornton,  Mission Specialist 1 (MS1/EV3)
      Claude Nicollier, Mission Specialist 2  (MS2)
      Jeff Hoffman, Mission Specialist 3 (MS3/EV1)
      Story Musgrave, Mission Specialist 4 (MS4/EV2)
      Tom Akers, Mission Specialist 5 (MS5/EV4)

Cargo Bay Payloads:    HST SM-01 (Hubble First Servicing Mission)

HST Replacements:    SA (Solar Arrays)
WF/PC-II (Wide Field/Planetary Camera-II)
RSU-1, 2 & 3 (Rate Sensor Units 1, 2 and 3)
ECU-1 & 3 (Electronic Control Units 1 and 3)
MSS-1 & 2 (Magnetic Sensing Systems 1 and 2)
COSTAR (Corrective Optics Space Telescope
   Axial Replacement)
SADE (Solar Array Drive Electronics)

Cargo Bay Equip:  HST FSS (HST Flight Support System)
          ORUC (Orbital Replacement Unit Carrier)
          SAC (Solar Array Carrier)
          SIPE (Scientific Instrument Protective Enclosures)
          ICBC (IMAX Cargo Bay Camera)

In-Cabin Payloads:IMAX (IMAX In-Cabin Camera)

Other:          AMOS (Air Force Maui Optical Site)

DTOs/DSOs:      DTO 648:  Electronic Still Camera
          DTO 656:  PGSC Upset Monitoring
          DTO 700-2:  Handheld Laser Ranging Device
          DTO 700-8:  Global Positioning System Flight Test
          DTO 1211:  Water Dumps at 10.2 psi Cabin
          DSO 326:  Window Impact Observation
          DSO 469:  Inflight Radiation Dose/Distribution
          DSO 483:  Back Pain in Microgravity
          DSO 485:  Inter-Mars Tissue Equivalent Counter
          DSO 487:  Immunological Assessment of Crew
          DSO 489:  EVA Dosimetry Evaluation
          DSO 604:  Visual-Vestibular/Function of Adaptation
           DSO 617:  Skeletal Muscle Performance
          DSO 624:  Cardiovascular Response to Exercise
          DSO 901:  Documentary Television
          DSO 902:  Documentary Motion Picture
          DSO 903:  Documentary Still Photography

STS-61 SPACE SHUTTLE ABORT MODES

    Space Shuttle launch abort philosophy aims toward safe and intact
recovery of the flight crew, orbiter and its payload.  Abort modes include:

* Abort-To-Orbit (ATO) - Partial loss of main engine thrust late enough to
permit reaching a minimal 105-nautical mile orbit with orbital maneuvering
system engines.

* Abort-Once-Around (AOA) - Earlier main engine shutdown with the capability to
allow one orbit around before landing at Edwards Air Force Base, Calif.

* TransAtlantic Abort Landing (TAL) - Loss of one or more main engines midway
through powered flight would force a landing at either Banjul, The Gambia,
Moron, Spain, or Ben Guerir, Morocco.

* Return-To-Launch-Site (RTLS) - Early shutdown of one or more engines, and
without enough energy to reach Banjul, would result in a pitch around and
thrust back toward KSC until within gliding distance of the Shuttle Landing
Facility.

     STS-61 contingency landing sites are the Kennedy Space Center, Edwards Air
Force Base, Banjul, Moron or Ben Guerir.




STS-61 VEHICLE AND PAYLOAD WEIGHTS

Vehicle/Payload                              Pounds

Orbiter (Endeavour) empty and 3 SSMEs                  173,014
Flight Support System (FSS)                      4,200
Imax Cargo Bay Camera (ICBC)                      608
Imax (in cabin)                              329
Orbital Replacement Unit Carrier (ORUC)                  6369
Solar Array Carrier (SAC)                      3829
Solar Array II                              702
Rate Sensor Units (3)                          73
Wide Field/Planetary Camera II                      613
Corrective Optics Space Telescope Axial Replacement   660
Electronic Control Units (2)                  35
Magnetic Sensing System (2)                  30
Co-processor                          140
Goddard High Resolution Spectrograph Redundancy Kit   7
Changeout complement total (launch)              2300
High-Speed Photometer                      603
WF/PC I                              624
Solar Array I                          668
RSU (3)                              73
ECU (2)                              35
Changeout complement total (Earth return)          2135
DSOs/DTOs                          104
Total Vehicle at SRB Ignition                  4,511,115
Orbiter Landing Weight                      209,383




STS-61 SUMMARY TIMELINE*

Flight Day One*

Ascent
OMS-2 burn (310 n.m. x 297 n.m.)
ICBC activation
NC-1 burn (310 n.m. x 302 n.m.)

Flight Day Two*

Remote Manipulator System checkout
Cabin pressurization to 10.2 psi
Space Support Equipment checkout/survey
Configure Flight Servicing Structure
NPC burn (310 n.m. x 302 n.m.)
NSR burn (310 n.m. x 304 n.m.)
Extravehicular Mobility Unit checkout
NC-2 burn (317 n.m x 305 n.m.)

Flight Day Three*

HST rendezvous operations
NH burn (320 n.m. x 305 n.m.)
NC-3 burn (320 n.m x 310 n.m.)
NCC burn (320 n.m. x 310 n.m.)
TI burn (320 n.m. x 312 n.m.)
HST grapple (320 n.m x 313 n.m.)
HST berth
HST survey
Group B powerdown

Flight Day Four*

HST Extravehicular Activity 1
(Hoffman and Musgrave:  Two Rate Sensor Units/Secondaries)

Flight Day Five*

HST Extravehicular Activity 2
(Thornton and Akers:  Solar Arrays)

Flight Day Six*

HST Extravehicular Activity 3
(Hoffman and Musgrave:  Wide Field/Planetary Camera; Two Magnetic
Sensing Systems)





Flight Day Seven*

HST Extravehicular Activity 4
(Thornton and Akers:  Corrective Optics Space Telescope Axial
Replacement/Secondaries)

Flight Day Eight*

HST reboost burns (320 n.m. x 313 n.m.)
HST Extravehicular Activity 5
(Hoffman and Musgrave:  Solar Array Drive Electronics/Secondaries)

Flight Day Nine*

Group B power up
HST grapple
HST unberth
HST release (320 n.m. x 313 n.m.)
Separation burns 1, 2 and 3 (320 n.m. x 311 n.m.)
Group B power down

Flight Day Ten*

Cabin pressurization to 14.7 psi
Off-duty half day (MS1, MS3, MS4, MS5)
Off-duty half day (CDR, PLT, MS2)

Flight Day Eleven*

Group B power up
Flight Control Systems checkout
Reaction Control System hot fire
Cabin stow

Flight Day Twelve*

Space Support Equipment power down
Deorbit preparations
Deorbit burn
Entry
Landing

*SPECIAL NOTE ON STS-61 SUMMARY TIMELINE

     On every Shuttle mission, some day-to-day replanning takes place to adjust
crew and event timelines according to unforeseen developments or simply to
optimize the use of time in orbit.

     During STS-61, the bulk of the daily replanning will be undertaken, while
the crew sleeps, by the planning shift in mission control.  During the EVA
days, this team will play a crucial role in making the most of the astronauts
time in Endeavour's payload bay.  To maximize crew productivity and to adapt to
any unexpected challenges, the planning team will have the ability to reorder
the sequence of individual tasks within any given spacewalk or to shift tasks
from one day's agenda to another.

     Each day's replanning effort will produce an execute plan defining the
approach for the next day's activities in space and on the ground.

STS-61 ORBITAL EVENTS SUMMARY

EVENT        START TIME    VELOCITY CHANGE          ORBIT
          (dd/hh:mm:ss)   (feet per second)          (n.m.)

OMS-2        00/00:45:00        461          310 x 297

NC-1        00/05:33:00        8          310 x 302
    (adjusts the rate at which Endeavour is closing on HST)

NPC         00/23:12:00        .5          310 x 302
    (fine-tunes Endeavour's ground track to be exactly in line with HST track)

NSR        01/03:57:00        5.5          310 x 304
    (adjusts Endeavour's closing rate on HST)

NC-2        01/04:32:00        12          317 x 305
    (adjusts Endeavour's closing rate on HST)

NH        01/17:22:00        4         320 x 305
    (adjusts altitude of Endeavour's orbital high point, fine-tunes course to
arrive at a point 40 nautical miles behind HST at same altitude)

NC-3        01/18:10:00        10          320 x 310
    (fired at 40 n.m. behind HST, begins closing in on HST; initiates closing
rate of about 16 n.m. per orbit aimed to arrive at a point 8 n.m. behind HST,
at same altitude as HST, two orbits later)

NCC         01/20:23:00        TBD         320 x 310
   (first burn calculated by onboard computers using onboard navigation
derived from orbiter star tracker sightings of HST; fired while orbiter is
about closing on point 8 n.m. behind HST to fine-tune course)

TI        01/21:23:00        3          320 x 312
   (fired upon arrival at point 8 n.m. behind HST; begins terminal
interception of HST)

MC1-MC4        TBD            TBD         TBD
   (mid-course corrections; calculated by onboard computers, double-
checked by ground; fine-tune final course toward HST, may or may required)

MANUAL        01/22:57:00        TBD            TBD
   (Begins about 45 minutes prior to HST grapple, less than 1 nautical mile
from HST.  Commander takes manual control of orbiter flight, fires braking
maneuvers to align and slow final approach)

GRAPPLE        01/23:42:00        n/a            n/a
   (HST captured with mechanical arm)

HST REBOOST    06/17:45:00        TBD            TBD
   (Performed only if amount of available propellant allows, lifts Endeavour's
orbit to reboost HST's orbit while HST is in cargo bay)

HST REBOOST    06/18:33:00        TBD            TBD
   (Performed only if amount of available propellant allows, lifts Endeavour's
orbit to reboost HST's orbit while HST is in cargo bay)

HST RELEASE    08/00:43:00        n/a            n/a
   (HST is released from Endeavour's mechanical arm)

SEP-1        08/00:44:00        1             320 x 313
   (Begins a slow separation of Endeavour from vicinity of HST)

SEP-2        08/01:08:00        2             320 x 313
   (Increases rate at which Endeavour is departing vicinity of HST)

SEP-3        08/01:32:00        3             320 x 311
   (Puts Endeavour on final course departing vicinity of HST)

DEORBIT        10/20:31:00        508

LANDING        10/21:45:00

NOTE: All planned burns are recalculated in real time once the flight is
underway using the latest information for the position of HST and will likely
change slightly.  Depending on how accurate the orbiter's navigation and course
is at certain times, some smaller burns listed above may not be required.
However, the times for major burns and events are unlikely to change by more
than a few minutes.

HUBBLE SPACE TELESCOPE/SERVICING MISSION-01
(HST-SM-01)

OVERVIEW OF MISSION

History

     Launched on April 24, 1990, NASAUs Hubble Space Telescope was designed to
be the most powerful astronomical observatory ever built.  And indeed, HST far
surpasses the capabilities of ground-based optical telescopes for many types of
research.  The keys to HubbleUs power are its operation in space, far above the
interference of the EarthUs atmosphere, and to the unique instruments it
carries as it orbits the planet.  In addition HST was the first observatory
designed for extensive on-orbit maintenance and refurbishment.

     While the launch on the Space Shuttle Discovery more than 3 years ago was
flawless, Hubble was not.  Two months after HST was deployed into orbit 370
miles (595.5 km) high, Hubble produced a disquieting discovery not about space,
but about itself.  The curvature of its primary mirror was slightly Q but
significantly Q incorrect.  Near the edge, the mirror is too flat by an amount
equal to 1/50th the width of a human hair.

     A NASA investigative board later determined that the flaw was caused by
the incorrect adjustment of a testing device used in building the mirror.  The
device, called a Rnull corrector,S was used to check the mirror curvature
during manufacture.

     The result is a focusing defect or spherical aberration.  Instead of being
focused into a sharp point, light collected by the mirror is spread over a
larger area in a fuzzy halo.  Images of extended objects, such as stars,
planets and galaxies, are blurred.

     NASA has been coping with HubbleUs fuzzy vision with computer processing
to sharpen images.  For bright objects, this technique has yielded breathtaking
detail never seen from the ground.  NASA also has been concentrating on the
analysis of ultraviolet light, which ground-based telescopes cannot see because
of the EarthUs intervening atmosphere.

     To realize the full potential of HST, however, the spacecraft must be
serviced.  The telescope mirror itself cannot be fixed or changed.  However,
corrective optics can be applied to the HST instruments to compensate for the
aberration, much the same as glasses or contact lenses correct human sight.
The new optics should allow Hubble to accomplish most, if not all, of it's
originally planned objectives.

     The mission, though, will accomplish much more than improved vision.
Hubble was designed to spend 15 years in space.  Even before the spherical
aberration was known, several servicing missions, including one in 1993, had
been planned so that failed parts could be replaced and others improved with
better technology.  This mission will perform that type of servicing in
addition to installing corrective optics.

     Endeavour will carry some 16,000 pounds (7,257 kilograms) of servicing
hardware into space.  During nearly 2 weeks in orbit around the Earth,
astronauts will use the Shuttle as a kind of orbiting service station from
which they will venture to work on the 12.5-ton (11.34-metric ton) telescope as
it hurtles around the planet at 18,000 miles (28,968 km) an hour.

     The crew will spend some 30 hours in space during at least five separate
spacewalk periods, undertaking a series of tasks more complex than any ever
attempted in orbit, to ensure that Hubble remains a viable and productive
national resource throughout its planned 15-year lifetime.

 Mission Objectives and Success

     The three objectives of the first Hubble servicing mission are to restore
the planned capabilities of the telescope by correcting the optics, to restore
reliability of the spacecraft and to validate that the concept of Hubble on-
orbit servicing is viable.

     The top priorities are installation of the replacement solar arrays; two
rate sensing units, one with an electronics control unit; the Wide
Field/Planetary Camera II (WF/PC-II) and fuses; the Corrective Optics Space
Telescope Axial Replacement (COSTAR); at least one new magnetometer; and a new
Solar Array Drive Electronics unit.

     For the first servicing mission to be considered fully successful, these
top priority items must be accomplished.  In addition, other tasks may be
performed on a time-available basis.  The minimum criteria for mission success
are to leave Hubble with three newer-design gyroscope systems and either an
operational WF/PC-II or COSTAR.

First Corrected Image Availability

     The first fully corrected Hubble images are estimated to be available 6 to
8 weeks after the servicing mission.  This time is necessary for adjustments to
ensure telescope stability and the best possible focus.  During this period,
telescope operators on the ground will remotely calibrate the gyros, which help
keep the HST fixed on its targets, and position the corrective mirrors in the
Corrective Optics Space Telescope Axial Replacement (COSTAR) and the Wide
Field/Planetary Camera 2 (WF/PC-II).

     COSTAR is being installed to remedy the blurred vision of three observing
instruments on HST. The WF/PC-II is a replacement camera that has its own
corrective optics.

     More information on activities after STS-61 necessary to produce a fully
corrected Hubble image can be found in the section on Servicing Mission Orbital
Verification.

Science Accomplishments

    Despite the flaw in the primary mirror, the bus-size Hubble still has
been able to gather a wealth of scientific data, most of which would have been
impossible to collect if the telescope did not exist.  In the last 3 years, HST
has conducted a variety of scientific investigations that have rapidly expanded
knowledge of what lies beyond the Earth, from the relatively nearby planets in
Earth's solar system to the most distant reaches of the universe.

    HubbleUs studies have ranged from Earth's neighbor Mars, to the
evolution of stars from birth to death, to the characteristics of galaxies
beyond, and finally to a field known as cosmology, which probes the fundamental
nature of the universe itself.

    The following is a small sampler of some of HubbleUs discoveries and
work in progress:

  % The Planets

    Even prior to the servicing mission, Hubble conducted and continues to
conduct long-term observations of global weather changes on Mars. Hubble has
observed the development of a rare, planet-wide storm on Saturn. The telescope
also resolved, as two distinct objects, the most distant planet in the solar
system, Pluto and its moon Charon. Previously, no telescope had been able to
separate clearly the two bodies.

    HST also has been studying long-term weather changes on Jupiter and its
auroral activity.  Hubble also has been measuring the extent of the atmosphere
of the Jovian moon Io and also has looked for changes in the satelliteUs
surface.

  % Stellar Evolution

    Hubble uncovered the strongest evidence yet that many stars form
planetary systems.  This evidence was the discovery of disks of dust around 15
newly formed stars in the Orion Nebula, a starbirth region 1,500 light- years
away.  Such disks are considered a prerequisite for the formation of solar
systems like Earth's. The HST images confirm more than two centuries of
speculation, conjecture and theory about the genesis of a solar system.

  % Star Clusters

    HST discovered young globular star clusters at the core of a peculiar
galaxy.  The discovery of these stars early in their evolution was the
equivalent of finding a RJurassic ParkS in space.

    The space telescope found Rblue stragglerS stars in the core of
globular cluster 47 Tucanae, providing evidence that some stars RcaptureS
others and merge with them.

  % Gallaxies

    HST uncovered circumstantial evidence for the presence of a massive
black hole in the core of the neighboring galaxy M32 as well as the giant
elliptical galaxy M87. Both galaxies have a central concentration of starlight
that probably is shaped by the gravitational field of the black hole.  This
implies that massive black holes may be quite common among RnormalS galaxies,
perhaps even Earth's.

    Hubble yielded direct evidence for galaxy evolution by resolving the
shapes of galaxies that existed long ago.  HST revealed that many ancient
spiral galaxies have since disappeared, possibly through fading or collisions
and mergers with other galaxies.

  % Cosmology

    The space telescope allowed astronomers to take a major first step in
determining the rate at which the universe is expanding.  HST detected 27 stars
called Cepheid variables.  These stars are Rstandard candlesS for estimating
distances to galaxies.  The expansion rate, known as the Hubble Constant, is
one of two critical numbers needed for making a precise determination of the
size, age and fate of the universe.

    HST discovered boron, the fifth lightest element, in a very ancient
star.  This star would have been one of the earliest formed after the Big Bang
explosion that most scientists believe began the universe.  If boron was
produced in the first few minutes of the birth of the universe, it implies that
the Big Bang was not a uniform explosion.

    Hubble precisely determined the ratio of deuterium to hydrogen in
interstellar gas clouds.  This value shows that the universe has only 6 percent
of the observable matter required to prevent itself from expanding forever.

European Space Agency (ESA) Role in HST

     The Hubble Space Telescope is a program of joint cooperation between NASA
and ESA. ESA provided Hubble's deployable solar arrays, the major source of
electrical power, which collects energy from the sun to recharge the
spacecraft's six nickel-hydrogen batteries.  ESA's second contribution was the
Faint Object Camera (FOC), which was intended for imaging of the faintest
objects in the visible and ultraviolet spectral regions at very high spatial
resolution.  These elements are discussed further in the section addressing
replacement hardware and instruments.

     Claude Nicollier, a mission specialist on this flight, is an ESA
astronaut.

SERVICING MISSION ORBITAL VERIFICATION (SMOV)

     The purpose of SMOV is to "recommission" HST so that it can begin science
operations as soon as possible following the first servicing mission.  This
involves a thorough engineering checkout of all serviced subsystems; optical
alignment and initial calibration of all science instruments; and the phasing
in of astronomical observations.  SMOV begins when HST is released from the
Shuttle and is expected to last approximately 13 weeks.

Key Activities During SMOV

  % Activation and engineering checkout of the science instruments.

  % Optical alignment and focusing of WF/PC-II and COSTAR.

  % Initial calibration of WF/PC-II and the COSTAR-corrected science
instruments.

  % Early science observations.

Engineering Checkout Activities

  % Decontaminate the WFPC II detectors (charge-coupled devices or CCDs) of any
foreign substances by heating the detectors to "drive-off" contaminants.

  % Establish proper operating temperature of WFPC II CCDs by monitoring
ultraviolet (UV) light from a calibration star.

  % Monitor pressure drop (due to outgassing) until it is safe to turn on high
voltage to the COSTAR-corrected science instruments.

  % Determine the effects of the servicing mission on the basic (pre-COSTAR)
optical performance of the science instruments.

Steps in Focusing the Science Instruments

  % Check out the first generation instruments and conduct prefocusing tests.

  % Adjust the secondary mirror in HST's Optical Telescope Assembly to set
focus for WF/PC-II and correct for residual coma in the Optical Telescope
Assembly.

  % Deploy COSTAR arms.

  % Adjust COSTAR and WF/PC-II optics and mirrors, including mirror tilt,
coarse adjustment, fine alignment and focus.

Science Instruments Calibration

  % A series of tests and measurements to establish the actual performance of
the science instruments in the areas of sensitivity, resolution and detector
response characteristics.



KEY HST SCIENTIFIC GOALS FOLLOWING THE FIRST SERVICING MISSION

  % Hubble will determine, precisely, the expansion rate of the universe by
measuring the light curve of Cepheid Variable stars in galaxies out to the
distance of at least 50 million light-years.

     Cepheids are pulsating stars that become alternately brighter and fainter
with periods (duration of the states of brightness or faintness) ranging from
10 to 50 days.  Astronomers have known for over 50 years that the periods of
these stars precisely predict their total luminous power, which allows their
distance to be measured.

     In the expanding universe, the Hubble Constant (Ho) is the ratio of the
recession velocities of galaxies to their distance. (Recession velocity is the
speed at which the galaxy is moving away from Earth.) The age of the universe
can be estimated from the Hubble Constant. The age currently is estimated to be
between 10 and 20 billion years, but a more precise measurement of the Hubble
Constant is required to narrow this range to an accuracy of 10 percent.

  % HST will look for the gravitational signature of massive black holes in the
cores of normal and active galaxies.  A black hole is a theoretical object that
is so compact and dense, nothing can escape its gravitational field.  The HST
spectrographs will measure precisely the velocities of gas and stars orbiting
the center of a galaxy.  If the stellar velocities increase rapidly toward the
galaxy center, it would be the signature of a massive, compact central object.

  % Hubble will be able to determine the shapes of galaxies that are very
distant.  Because remote objects also are relics of the early universe, HST
will be able to study how galaxies have evolved since the beginning of the
universe.  Nearby galaxies have spiral, elliptical and irregular shapes,
however, these shapes should have changed over time because the universe is
evolving.

  % Hubble will be able to precisely measure the ages of globular clusters by
observing the faintest stars in the clusters.  Globular clusters are considered
to be the oldest objects in the universe, and their ages provide insights into
how stars evolve and also provide an independent estimate of the age of the
universe.

HUBBLE SPACE TELESCOPE RENDEZVOUS AND RETRIEVAL

     The rendezvous and retrieval operaTelescope will be similar to those
conducted on previous missions requiring capture of a free-flying satellite in
orbit.

     For the HST mission, Endeavour's crew will perform many orbit adjust burns
to catch up with and retrieve the telescope on flight day three of the mission
using the Shuttle's robot arm.

     Once the Shuttle is safely in orbit and the payload bay doors opened, the
space support equipment activation is performed.  This includes activating the
flight support system and orbital replacement unit carrier heaters.  Other
pre-rendezvous activities will include checkout of the robot arm, the orbiter
Ku-band dish antenna used as a radar system during rendezvous and the ground
command system.

     The terminal initiation burn occurs about 2 hours prior to capture at a
distance of approximately 40,000 feet (12,192 m) in front of the telescope.
Several small mid-course correction burns follow before the Commander takes
over manual control of the Shuttle about 1,200 feet (366 m) below and 500 feet
(152 m) behind the telescope.

     The orbiter approaches Hubble from underneath, just after orbital sunset.
This approach technique is designed to minimize potential contamination from
the Shuttle's thruster firings.

     Prior to capture, a ground-commanded maneuver of the telescope will be
performed to align the grapple fixture on the HST with Endeavour's robot arm.
The size of the telescope maneuver will depend on the angle to the Sun and
ranges from about 70 degrees to 180 degrees.

     When the telescope is grappled, using the robot arm's end effector, it
will be lowered into the payload bay and berthed in the flight support system,
a turntable likened to a lazy susan for its rotation and tilt ability to assist
in the servicing tasks.  An electrical cable is remotely attached to provide
orbiter power to the telescope.

COMMANDS TO HUBBLE

     Commands to HST are issued from the Space Telescope Operations Center
(STOCC) at Goddard Space Flight Center, Greenbelt, Md., which manages the
orbiting observatory.  The STOCC has been the nerve center for Hubble
operations since the telescope was launched.  Commands to Hubble are issued
from the STOCC and data gathered by the spacecraft arrive there first.

     The STOCC is responsible for most commanding of the HST during STS-61,
although the crew can send a limited number of commands from Endeavour. The
STOCC will send commands configuring the space telescope for retrieval by the
orbiter; integrate commands with crew activities during extravehicular
activispacecraft hardware and perform hardware checkouts and send commands to
configure the space telescope for deployment from Endeavour.

STS-61 EXTRAVEHICULAR ACTIVITIES

     A total of five spacewalks are planned on STS-61 to service the HST.
Unlike past Shuttle repair work performed on satellites such as Intelsat on
STS-49, HST was designed with the objective of servicing it in orbit through
Shuttle spacewalks.  As such, it has two grapple fixtures for the Shuttle's
mechanical arm, many handholds for spacewalkers and bolts and electrical
connections designed to be serviced by a spacewalker.

     However, the amount of work to be performed on STS-61 has increased above
what originally was projected for the first servicing flight to the telescope
due to deficiences and equipment problems that have occurred or been discovered
since HST was launched.  Since there is such a large amount of work to be
accomplished on STS-61, the various tasks have been prioritized by the HST
program officials.

     The primary tasks on STS-61 will be to install two Rate Sensor Units, one
with an Electronics Control Unit, the Solar Arrays, the Solar Array Drive
Electronics, the Wide Field/Planetary Camera and four instrument fuse plugs,
the Corrective Optics Space Telescope Axial Replacement and one Magnetic
Sensing System.

     Secondary tasks that may be performed during the spacewalks if time
permits include installing the Goddard High Resolution Spectrograph Redundancy
Kit, a 386 Coprocessor, a second Magnetic Sensing System, four gyro Fuse Plugs
and one Electronic Control Unit. A third Rate Sensor Unit is being carried in
the payload bay for use if needed.

     The spacewalks will be peformed by STS-61 extravehicular crew members Jeff
Hoffman, Story Musgrave, Kathy Thornton and Tom Akers. Each spacewalk will be
performed by two crew members, one of whom will be in a foot restraint mounted
at the end of Endeavour's mechanical arm.  During all EVAs, the crew member
mounted at the end of the arm will be referred to as Extravehicular Crew Member
2, or EV2, while the other spacewalker will be designated EV1.

     The EVA crew can be distinguished by markings on the legs of their
spacesuits.  Hoffman will have a solid red stripe around the legs of his suit;
Musgrave will have no stripes on the legs of his suit; Thornton will have a
dashed red stripe around the legs of her suit; and Akers will have a diagonal,
broken red stripe around the legs of his suit.

     In planning for the mission, the EVAs have been designed to take into
account the possibility that crew members may encounter unforeseen difficulties
either in tasks or equipment that could cause the preplanned schedule for
installation of various equipment to change.  All four EV crew members have
cross-trained so that any one is capable of performing any given task.

     For all of the various tasks, the Flight Support Structure in Endeavour's
cargo bay on which HST will be mounted, once it is retrieved, will be rotated
so the area being worked on faces forward to allow better visibility.  Those
specific tasks and the EVA work required to complete them are described in the
following sections.

REPLACEMENT HARDWARE AND INSTRUMENTS

     While the servicing mission is complex, steps have been taken to make the
spacecraft as straightforward to work on as possible.  Since HST was designed
for servicing in space from it's inception, many of its subsystems are modular,
standardized and accessible.  Hubble has 49 different modular subsystems
designed for servicing, ranging from small fuses to large scientific
instruments.  The space telescope, which is 43.5 feet (13.25 meters) long, also
has 225 feet (69 meters) of handrails and 31 footholds to aid astronauts in
servicing tasks.  And more than 200 tools Q from screwdrivers to hardware
designed specifically for HST servicing Q are available for use on this
mission.

     NASAUs Goddard Space Flight Center, Greenbelt, Md., is responsible for the
components that will be serviced or replaced on Hubble. The components make up
a primary servicing task list that will be carried out during the mission,
followed by a secondary task list to be undertaken if time and conditions
allow.

     The missionUs primary objective is to restore the HSTUs science
capabilities with the Wide Field/Planetary Camera-II and the Corrective Optics
Space Telescope Axial Replacement, both of which will compensate for the
spherical aberration of the primary mirror.

     However, the replacement of the spacecraftUs solar arrays Q HSTUs major
source of electrical power Q tops the primary servicing task list.  This is
because solar array jitter, or excessive flexing, may be compromising the
structural integrity of the arrays.  By replacing the arrays first, the
observatory still will be able to perform science even if an emergency causes
the mission to be called off and forces astronauts to release the telescope
from the Space Shuttle before installing the optics packages

     Likewise the replacement of one gyro pair is second on the task list,
because if more gyros fail, the pointing of the spacecraft at science targets
cannot be accurately controlled.

The primary servicing task list includes:

   %  Solar Array II (SA II).
   %  Gyro Pair 2.
   %  Wide Field Planetary Camera 2 (WFPC2) and four instrument fuse plugs.
   %  Corrective Optics Space Telescope Axial Replacement (COSTAR)
   %  Magnetometer System 1.
   %  Gyro Pair 3 with Electronics Control Unit (ECU).
   %  Solar Array Drive Electronics 1 (SADE).

The secondary servicing task list includes:

   %  A redundancy kit for the Goddard High Resolution Spectrograph (GHRS).
   %  The 386 co-processor on the spacecraftUs primary computer, called the
          DF-224.
   %  Magnetometer System  2
   %  Four gyro fuse plugs.
   %  Electronics Control Unit for Gyro Pair 1.




PRIMARY SERVICING TASKS

Gyroscope Pairs (Rate Sensing Units) and Electronics Control Unit

     Three gyroscopes (or gyros) are required to point and track HST. Three
more gyros are onboard as backups.  The total of six gyros are packaged in
pairs of two, called Rate Sensing Units (RSU).  One gyro failed in December
1990; a second failed in June 1991 and a third in November 1992.

     Two of these three gyros, one located in pair 2 and the other in pair 3,
contain hybrid electronics that are suspected of causing the failures.  Gyro
pairs 1 and 3 also have experienced a failure in one channel of their
Electronics Control Unit (ECU), the cause of which is suspected to be a random
electronic part failure.  While these failures have not affected HSTUs
performance, replacing the failed hardware will increase system reliability.

     The Rate Sensor Units are inside the housing of HST. To begin the
replacement work, the spacewalking astronaut, standing in a foot restraint
mounted on the end of the Shuttle's mechanical arm, will first back out several
bolts to open doors covering the star tracker near the base of HST. One of the
four bolts holding the doors, called the star tracker seal, must be completely
removed to unlatch the doors.

     A programmable power wrench will be used to loosen and tighten all bolts
during the RSU replacement.  While the arm-mounted astronaut unlatches the
doors, his fellow spacewalker, mounted on a foot restraint attached to a
support structure in the Shuttle's bay, will assist.  Once the doors are
unlatched, they will be swung open to provide access to the bay area.

     The Rate Sensor Units are located behind the cone-shaped star tracker
shades in the bay area of the telescope.  To replace an RSU, these shades may
have to be removed.  If so, three bolts must be loosened and the shade pulled
off.  The shade then can be temporarily stowed outside the work area.  The
shades are reinstalled by pushing them back into place and then retightening
the three bolts.

     To remove an RSU, the spacewalker, standing in an adjustable foot
restraint attached to the telescope, will loosen three bolts and disconnect two
electrical plugs.  The RSU then may be removed by holding a handrail located at
the top of the unit.

     During these activities, the astronaut standing on the end of the arm will
assist his partner from behind.  The new RSU, carried aloft in an Orbital
Replacement Unit Carrier (ORUC) in the Shuttle's bay, will be installed by
sliding it into place and then retightening the three bolts and hooking up the
two electrical plugs.

     The time required to set up, remove two RSUs, install two RSUs and then
clean up the area during training has been around 3.5 hours, including the
possible removal and reinstallation of the star tracker shades.

Electronic Control Units

    The Electronic Control Units are the electrical brains for the Rate
Sensor Units and are located in a service bay on the Hubble Space Telescope.
Once the compartment door is opened, two of the three ECUs will be replaced by
removing four bolts and disconnecting each one's electrical cable.  The new
units, which are retrieved from a protective container in the payload bay, will
be installed in a similar fashion.

Solar Array II

     The Solar Arrays were built in Europe under the auspices of ESA. The solar
arrays provide the telescope and its instruments with 5kW of electrical power
at the start of their lifetime.  They constitute the spacecraft's two "wings"
and consist of 50,000 silicon photoelectrical cells, covering a surface area of
84 square yards/6.6 x 39.6 x 9.24 ft (70 square meters/2 x 12 x 2.8 m).

     The arrays are the flexible "roll-out and roll-up" type and are made of
huge sheets of plastic (fiberglass-reinforced Teflon) held in place by
horizontal metal struts, which also unroll.  Each wing weighs about 352 pds
(160 kg).

     But the arrays create a jitter that interferes with spacecraft stability
and affects its pointing capability.  The arrays now on Hubble were supposed to
accommodate the expansion and contraction caused by heating and cooling as the
space telescope moves in and out of daylight during its 96-minute orbits.
However, a compensation device that allows for the expansion and contraction of
the solar array blankets does not expand and contract as smoothly as expected.

     As a temporary fix, engineers created software that commanded Hubble's
pointing system to compensate for the jitter automatically.  This procedure
occupies a large portion of the on-board computer memory, though, and to truly
fix the problem, the solar arrays must be replaced.

     ESA redesigned and provided to NASA a set of spare solar arrays to reduce
the jitter to an acceptable level.  This set will be installed on the HST after
the existing arrays are removed; the arrays now on the spacecraft will be
returned to Earth. To significantly reduce jitter, the new arrays have thermal
insulation sleeves on the array supports, called bi-stems, to minimize heating
and cooling of the support during each orbit.  Springs that work like shock
absorbers also will take up tension at the array ends.

     To replace the HST Solar Arrays, first the old arrays are retracted by
commands from the Space Telescope Operations Control Center. Once they have
been retracted and stowed, the arm-mounted spacewalker will release three
latching points on the first array to be removed.  Once the three latches have
been released, the array can be removed and handled using a transfer handhold
mounted to the array.

     The array then is carried by having the mechanical arm moved to position
the astronaut within reach of a temporary stowage bracket for the old arrays,
mounted on the right-hand side of the Solar Array Carrier in Endeavour's cargo
bay.  While being moved from place to place at the end of the arm, the crew
member also may evaluate the handling characteristics of the array to prepare
for carrying the new array up to its installation position.  Thoughout the
removal operation, the arm-mounted astronaut will be assisted by his
counterpart, who will be moving about via handholds on the telescope and
Shuttle.

     The new solar array is removed from the SAC by disconnecting a power and a
data connection and then unlatching three latch points exactly like the latch
points on the telescope.  A temporary transfer handle allows the arm-mounted
astronaut to carry the new array up to the installation location.  His
counterpart will assist with the installation by standing in a foot restraint
mounted to the telescope near the work area.

     While the array is being transported, the power and data connectors are
secured in temporary holding brackets on the array.  To install the new array,
first it is moved into position and once seated, the three latch points are
locked in place and the connectors plugged in.  The second array is removed and
its replacement installed in exactly the same fashion.

     During training, the time required to perform a changeout of the solar
arrays was about 5 hours, and one full spacewalk is dedicated to this task.
The new arrays are not planned to be deployed during the spacewalk performed to
install them.

Wide Field/Planetary Camera-II (WF/PC-II)

     The current WF/PC has been used to study bright, high-contrast objects,
such as major solar system planets and nearby star clusters and galaxies.
Spherical aberration, however, has hampered the ability of the camera to
provide high-resolution images of the very faintest objects, or objects in a
field crowded with other objects.

     The WF/PC-II is a spare instrument developed, beginning in 1985, by the
Jet Propulsion Laboratory (JPL) team, Pasadena, Calif., that built the first
WFPC. When HubbleUs mirror was found to be flawed, NASA and the WFPC science
team immediately began working on an optical correction that could be built
into WFPC2. The new design incorporates an optical correction by the refiguring
of relay mirrors already in the optical train of the cameras.  Each relay
mirror is polished to a new RprescriptionS that will compensate for the
incorrect figure on HSTUs primary mirror.  Small actuators will fine- tune the
positioning of these mirrors on orbit, ensuring the very precise alignment that
is required.

     Through a servicing bay door built into the side of HST, astronauts will
slide out the 610-pound (277-kilogram), wedge-shaped WFPC, as they would a
giant drawer, and replace it with WFPC2. The removed WFPC will be returned to
Earth.

     The WFPC2 will have three wide-field cameras and one planetary camera
instead of the original total of eight.  The WFPC2 team chose to reduce the
number of cameras to four in order to develop a system to align the corrective
relay mirrors on-orbit.  Improved Charged Coupled Devices (CCDs) are
incorporated into WFPC2 to improve its sensitivity, particularly in the
ultraviolet.

     To remove and replace the Wide Field/Planetary Camera (WF/PC), the doors
to the service bay at the base of the telescope are opened and specially
designed guide rails are installed to assist with removal of the instrument.

     A temporary handhold then is installed on the WF/PC. Using this handhold,
the arm-mounted spacewalker pulls the WF/PC out of its installed position while
his counterpart watches the alignment of the WF/PC on the rails and ensures it
is level as it is removed.  Once removed from the telescope cavity, the
arm-mounted astronaut is positioned within reach of a temporary parking fixture
for the old WF/PC in Endeavour's cargo bay, where it is stowed.

     A temporary handhold is installed on the new unit, WF/PC-II, in its
Scientific Instrument Protective Enclosure (SIPE) in Endeavour's cargo bay.
The WF/PC-II is pulled from the SIPE by the arm-mounted crew member, who is
later moved to the installation site by the arm operator.  Meanwhile, the SIPE
door is temporarily latched by his crew mate.

     Before sliding the WF/PC-II into place inside the telescope, a cover over
its mirror is removed.  Then, the arm-mounted spacewalker slides it into the
telescope slot while his fellow spacewalker checks to ensure that it is aligned
on the guide rails.  Once inserted in place, the handhold is removed from the
instrument and the guide rails are detached.

     Finally, the old WF/PC is removed from its temporarily stowed postion in
the parking fixture and inserted into the SIPE that carried WF/PC-II, where it
is secured for Endeavour's trip home.

     Removal of the old WF/PC and the installation of WF/PC-II has taken about
4 hours and 15 minutes during training.

Coorective Optics Space Telescope Axial Replacement (COSTAR)

     COSTAR is designed to optically correct the effects of the primary mirror
aberration on three instruments besides the WFPC: the Faint Object Camera
(FOC), the Faint Object Spectrograph (FOS) and the Goddard High Resolution
Spectrograph (GHRS).

     The FOC, provided by ESA, is designed to detect very low-luminosity
celestial bodies and to provide the most detailed images on HST. It consists of
an electronic conventional scanning camera (of the television type), whose
front part is a powerful image intensifier tube.  Its performance has been
degraded by the spherical aberration, but the sharp image cores still allow the
camera to detect details not seen by ground-based telescopes.


     The FOS analyses the light from very faint objects in the visible and
ultraviolet spectral regions.  While the faintest objects now cannot be
reached, observations of brighter sources are only moderately degraded.

     The GHRS is intended for very detailed analysis of ultraviolet radiation.
The instrument now loses spectral resolution on the faintest objects, but
observations of brighter sources are only moderately degraded.

     COSTAR was invented by the Hubble Space Telescope Strategy Panel, a group
of scientists and engineers brought together at the Space Telescope Science
Institute, Baltimore, Md., in the fall of 1990 to consider how to fix HST.
Built by Ball Aerospace, Boulder, Colo., under contract to NASA, COSTAR has no
detectors or cameras.  It will use precisely shaped mirrors, ranging from about
the size of a dime to a quarter, to correct for the spherical aberration.

     Through a servicing bay door, astronauts will pull out the 487-pound
(221-kilogram), phone booth-size High Speed Photometer (HSP) and install in its
place the identically sized COSTAR. Once in place, COSTAR will deploy a set of
mechanical arms, no longer than a human hand, that will place corrective
mirrors in front of the openings that admit light into the Faint Object Camera,
the Faint Object Spectrograph and the Goddard High Resolution Spectrograph.
COSTARUs corrective mirrors will refocus light relayed by HSTUs primary mirror
before it enters these three instruments.  COSTAR will restore the optical
performance of these instruments very close to the original expectations.

     To install COSTAR, the spacewalkers first will open doors to the bay, that
enclosed the HSP, by loosening several bolts.  Once the doors are open, latches
that hold the HSP in place will be loosened and then four electrical connectors
and a ground strap will be disconnected from the instrument.

     Then the HSP is lowered from its position to guide rails for the unit.
The arm-mounted spacewalker and his crew mate, standing in a foot restraint
attached to the telescope, will coordinate efforts to remove the device.  The
arm-mounted crew member will slide HSP out while his fellow spacewalker ensures
that it is aligned with the guide rails.

     Once removed, the HSP is held by the crew member standing on the end of
the arm while the arm is positioned so the HSP can be placed in a temporary
parking fixture mounted in the cargo bay.  After it is temporarily stowed, a
handhold is attached to COSTAR and it is lifted from its protective enclosure.
A ground strap is disconnected and, while the arm-mounted astronaut is lifting
COSTAR out, his crew mate is assisting by ensuring COSTAR is squarely aligned
with the enclosure as it is extracted.

     The arm-mounted crew member then is positioned up to the installation area
while his fellow spacewalker moves to the site via handrails on the telescope.
COSTAR then is aligned with the guide rails, with the arm- mounted spacewalker
watching the alignment of a rail at the upper left-hand corner of COSTAR and
his counterpart checking the alignment of a rail at the lower right corner.

     Once COSTAR slides into place, the four electrical connections,
disconnected from HSP, are connected to COSTAR along with the grounding strap,
and the latches are tightened to hold COSTAR in place.

     In training, removal of the HSP and installation of COSTAR has taken about
3 hours and 15 minutes.

Solar Array Drive Electronics 1 (SADE)

     Each solar array wing has an electronics control assembly that includes a
drive electronics unit.  These units transmit positioning commands to the wing
assembly.  One of these Solar Array Drive Electronics units has failed due to
transistor overheating.  A replacement SADE, provided by ESA, will restore that
lost capability and provide better heat protection for the transistors.

     The Solar Array Drive Electronics are mounted on the inner side of one of
the doors to an HST service bay.  Two electronics boxes are mounted on the
inside of the door, but only one is being replaced.  Once the door is opened,
the two spacewalkers - one mounted on the arm and one holding handrails on the
telescope - will loosen six bolts to free the old SADE unit and disconnect
electrical connectors attached to the unit.  The new SADE unit is installed in
the reverse of this process.

Magnetometer System 1

     The HSTUs two magnetometers (also known as magnetic sensing systems)
measure the spacecraftUs relative orientation with respect to the EarthUs
magnetic field.  Neither magnetometer is functioning at full capability.  Both
replacements have improved electronics and thermal blankets added.  The
replacement magnetometers will be snapped into place over the existing
magnetometers, which will not be removed from the HST.

     Both of the magnetic sensing systems are located near the top of the
telescope near the aperture door.  The new units will be installed using four
rotating knob connectors and will be attached directly on top of the old units
by removing some insulation and removing and reinstalling the electrical cable.
These units are used to help measure the observatory's position relative to
Earth's magnetic field.

Fuse Plugs

     Fuses for both the gyros and instruments will be replaced to correct
sizing and wiring discrepancies.

     The fuses that will be replaced on the HST are located on the inside of a
compartment door.  Eight of the fuse plugs will be removed and replaced by the
spacewalking astronauts.  Once all have been replaced, checks will be made to
ensure they are working properly.


SECONDARY SERVICING TASKS

Co-Processor

     The DF-224 is the HSTUs flight systems computer.  One of the computerUs
six memory units has failed and another has partially failed.  Hubble requires
only three memory units to fully function, so the failures have not affected
telescope operations.  However, to restore the memory redundancy and augment
the telescopeUs memory capacity and speed, a co- processor, based on
386-computer architecture, will be integrated into the flight systems computer,
which will increase both flight computer memory and the speed of some
operations.

     The DF-224 co-processor will be installed on top of the HST computer
located in a compartment on the telescope.  The memory upgrade is installed
using handles on the computer and attaching four bolts using a power tool.

Goddard High Resolution Spectrograph Redundancy Kit

      The GHRS has two detector systems.  Because of the anomalous behavior of
a low-voltage power supply, the side-one detector no longer is used.  The
redundancy kit consists of an externally mounted relay box that enhances system
redundancy so that the side-one detector can be used and the side- two
detectors will not be compromised if the anomaly recurs.

     Made up of four cables and a relay box, the Goddard High Resolution
Spectrograph redundancy kit is designed to bypass an erratic detector system on
the science instrument located in an instrument bay on the lower portion of the
HST. The relay box is installed first using a power tool similar to an electric
drill.  This is followed by attachment of the four cables.

HUBBLE SPACE TELESCOPE TOOLS AND CREW AIDS

     The crew of STS-61 has more than 200 tools and crew aids with them for the
servicing of the Hubble Space Telescope. The tools and crew aids, known as
Space Support Equipment (SSE) hardware, range from a simple bag for carrying
some of the smaller tools to sophisticated, battery operated power equipment.
These tools will be used by the EVA crew members servicing the spacecraft.

Crew Aids

     Crew aids are defined as those that are fixed in place and those that are
portable equipment items but not hand tools, used to assist crew members in
accomplishing servicing mission tasks.  SSE equipment crew aids permit the crew
members to maneuver safely or to restrain themselves, transfer Orbital
Replacement Units (ORUs) and other portable items, protect equipment and
themselves during changeout activities and temporarily stow or tether equipment
during EVAs.


     Examples of crew aids are handrails, handholds, translation devices,
transfer equipment, protective covers, tethering devices, grapple fixtures,
foot restraint sockets and stowage and parking fixtures.

Tools

     Tools are hand-operated or manipulated devices that allow the EVA
astronauts to increase the efficiency of performing intricate, labor-intensive
tasks.

Stowage

     The tools and crew aids will be stowed on or in the Solar Array Carrier
(SAC), Orbital Replacement Unit Carrier (ORUC), Flight Support System (FSS),
HST Tool Box, Sidewall-mounted adapter plates, Provisions Stowage Assembly
(PSA), an Adaptive Payload Carrier (APC), middeck lockers, aft flight-deck and
airlock.  Tools and crew aids are provided by Johnson Space Center, Houston,
and Goddard Space Flight Center, Greenbelt, Md.

Uses

     Tools and crew aids considered Rgeneral,S with a wide variety of uses,
include the Power Ratchet Tool (PRT), Multi-setting Torque Limiter (MTL),
adjustable extension with 7/16th-inch sockets, ingress aids, portable work-
light receptacle and a locking connector tool.  More specific, but still
considered general, items are a low-gain antenna (LGA) cover, umbilical
connector covers, a flight support system (FSS), berthing and positioning
system (BAPS), support post and a multi-layer insulation (MLI) repair kit.

    To be used on the changeout of the Wide Field Planetary Camera 2 (WFPC2)
are the WFPC handholds, WFPC guide studs, quick-release zip nuts, WFPC pick-off
mirror cover, forward fixture, aft fixture and the HST radial bay cover.

     For the High Speed Photometer (HSP) replacement with the Corrective Optics
Space Telescope Axial Replacement (COSTAR), tools and aids to be used will be
the COSTAR contamination cover, a COSTAR handling aid, an HSP handling aid,
forward fixture, aft fixture and an axial Science Instrument Protective
Enclosure (SIPE) safety bar.

     For the solar array replacement, the astronauts will use articulating foot
restraints, solar array primary drive mechanism handles, solar array temporary
stowage brackets (TSBs), solar array transfer handles, solar array jettison
handle, solar array spines, Portable Flight Release Grapple Fixture (PFRGF) and
a Marmon clamp.

     For the changeout of the gyro rate sensor units, crew members will use a
Portable Foot Restraint (PFR) socket converter (90-degree), Fixed-Head Star
Tracker (FHST) light shade covers and a FHST delta plate cover.


Portable Foot Restraint

     There are two Hubble Space Telescope portable foot restraints built for
use on the STS-61 mission.  These restraints are used by the spacewalking
astronauts during the five extravehicular activities to provide a stable
platform from which to work.  Both restraints are stowed in the payload bay,
one on the left side and the other on the flight support system.


Tool Box

    The HST tool box is designed to stow individual tools, tool boards and tool
caddies that will be used throughout the mission.  The box is mounted on the
right side of the payload bay.  Each tool inside the box is stowed in a
specific location with markings to assist the astronauts in the retrieval and
stowage.

Power Ratchet Tool (PRT)

     The Goddard-provided power ratchet tool (PRT) is powered by a 28-volt
battery.  Made of titanium and aluminum, the 17-inch (43-centimeter) tool will
be used for tasks requiring controlled torque, speed or turns and can be used
where right-angle access is required.  It will provide 25 foot-pounds of
pressure in the motorized mode and 75 foot-pounds of pressure in the manual
mode.  It has a speed of 10 to 30 revolutions per minute.  A spare power
ratchet will be carried on the mission, as will spares for all other tools to
be used by the astronauts.

HST Power Tool

    This tool is a modified, battery-operated power tool with torque and rpm
control.  The design includes a 3/8-inch drive fitting, forward and reverse
drive rotation, torque ranges from 50 to 300 inch-pounds and a bracket for
mounting the tool to the spacesuit.

Mini-Power Tool

     The mini-power tool is a battery-operated screwdriver intended for use
when a larger power tool is not required and when work space is limited.  It
can be used as a power tool or with the power off, the output shaft is locked
automatically for use as a manual driver.

Multisetting Torque Limiter

     This tool is provided to prevent damage to hardware due to the application
of torque which may exceed the design limits.  Multisetting torque limiters are
used in conjunction with the power tools or hand tools that interface with
bolts and latches on the telescope.




Adjustable Extensions

     Several extensions were designed to be adjustable to ease the movement of
the astronauts while reducing the time required for tool changeouts.  The
adjustable extensions replace several fixed length extensions by providing
adjustment from 12 to 16.5 inches.  Another adjustable extension provides
lengths from 15 to 24 inches.  When retracted, these extensions reduce the
potential for damage to other hardware.





IMAX

     THE IMAX project is a collaboration between NASA and the Smithsonian
Institution's National Air and Space Museum to document significant space
activities using the IMAX film medium.  This system, developed by IMAX Systems,
Corp., Toronto, Canada, uses specially designed 70mm film cameras and
projectors to record and display very high definition large- screen pictures.

     An IMAX camera system will be flown on Shuttle Mission STS-61 and will be
used by Endeavour's crew to collect material for upcoming IMAX productions.
IMAX cameras have flown on several Shuttle missions and film from those
missions was used to form the IMAX productions The Dream is Alive and The Blue
Planet.

In-Cabin IMAX Camera Equipment

     The IMAX system consists of a camera, lenses, rolls of film, two magazines
with film, an emergency speed control, a Sony recorder and associated
equipment, two photographic lights, supporting hardware in the form of mounting
brackets to accommodate the mode of use, two cables and various supplemental
equipment.

     The IMAX and supporting equipment are stowed in the middeck for in- cabin
use.  The IMAX uses two film magazines which can be interchanged as part of the
operation.  Each magazine runs for approximately 3 minutes.  When both
magazines are consumed, reloading of the magazines from the stowed supply of
film is required.  Lenses are interchanged based on scene requirements.  The
IMAX will be installed in the orbiter middeck approximately 7 days prior to
launch.

IMAX Cargo Bay Camera (ICBC)

     During Shuttle Mission STS-61, an IMAX Cargo Bay Camera (ICBC) will be
carried in the payload bay of Endeavour and used to document activities
associated with the servicing of the Hubble Space Telescope. The camera is
mounted in a pressure sealed container with a viewing window.  The window has a
sliding door which opens when the camera is in operation.  The camera is
controlled from the aft-flight deck, exposing the film through a 30mm fisheye
lens.

STS-61 IN-CABIN PAYLOADS

AIR FORCE MAUI OPTICAL SYSTEM

     The Air Force Maui Optical System (AMOS) is an electrical-optical facility
on the Hawaiian island of Maui. No hardware is required aboard Discovery to
support the experimental observations.  The AMOS facility tracks the orbiter as
it flies over the area and records signatures from thruster firings, water
dumps or the phenomena of "Shuttle glow," a well-documented fluorescent effect
created as the Shuttle interacts with atomic oxygen in Earth orbit.  The
information obtained by AMOS is used to calibrate the infrared and optical
sensors at the facility.

DTO-667: PILOT INFLIGHT LANDING OPERATIONS TRAINER (PILOT)

     One of the challenges to flying long duration Shuttle missions is the
issue of orbiter landing tasks requiring a high level of skill and proficiency
yet data showing that a pilot's landing skills degrade after an extended
absence from a landing trainer such as the Shuttle Training Aircraft. During
Shuttle Mission STS-61, a portable scientific workstation designed to aid the
Shuttle commander and pilot in maintaining those landing skills will be
demonstrated for the second time.

     The PILOT system hardware, which flew on Shuttle Mission STS-58 in October
1993, consists of a portable scientific workstation, a high resolution color
display and a hand controller with orbiter look and feel.  The software used in
the system was transferred from the Shuttle Engineering Simulator software
which is used to validate Shuttle flight software.  This provides PILOT with
orbiter handling and guidance characteristics.

     The PILOT system is stowed in lockers on the flight deck and middeck areas
of the Space Shuttle. When a member of the crew wants to use the system, the
workstation is mounted on a counsole directly in front of the pilot's seat on
the flight deck and the PILOT system hand controller is attached to the
orbiter's hand controller.

     In addition to evaluating the ability to maintain landing skills of a
Shuttle crew in Earth-orbit, the PILOT system may be integrated into the
standard training activities of all Shuttle crews at the Johnson Space Center
in Houston.


STS-61 CREW BIOGRAPHIES

     Richard O. Covey, 47, Col., USAF, is Commander (CDR) of STS-61. Selected
as an astronaut in January 1978, Covey considers Fort Walton Beach, Fla., his
hometown and will be making his fourth space flight.

     Covey graduated from Choctawhatchee High School, Shalimar, Fla., in 1964;
received a bachelor of science degree in engineering sciences with a major in
astronautical engineering from the U.S. Air Force Academy in 1968, and a master
of science degree in aeronautics and astronautics from Purdue University in
1969.

     Covey first flew as Pilot for Shuttle mission STS 51-I in August 1985.  He
next flew as Pilot on STS-26 in September 1988.  On his most recent flight, he
was Commander for STS-38 in November 1990.  Covey has logged over 385 hours in
space.

     Kenneth D. Bowersox, 37, Cmdr., USN, will serve as Pilot (PLT).  Selected
as an astronaut in June 1987, Bowersox was born in Portsmouth, Va., but
considers Bedford, Ind., his hometown and will be making his second space
flight.

     Bowersox graduated from Bedford High School, Bedford, Ind.; received a
bachelor's degree in aerospace engineering from the Naval Academy in 1978 and a
master of science degree in mechanical engineering from Columbia University in
1979.

     Bowersox first flew as Pilot for Shuttle mission STS-50 in June 1992.  He
has logged over 331 hours in space.

     Tom Akers, 42, Lt. Col., USAF, will serve as Mission Specialist 5 (MS5)
and as one of the extravehicluar activity crew members.  Selected as an
astronaut in June 1987, Akers was born in St. Louis, Mo., but considers
Eminence, Mo., his hometown and will be making his third space flight.

     He graduated from Eminence High School and received bachelor and master of
science degrees in applied mathematics from the University of Missouri-Rolla in
1973 and 1975, respectively.

     Akers served as a mission specialist on STS-41 in October 1990.  His next
flight was as a mission specialist on STS-49 in May 1992.  Akers was one of the
EVA crew members of a three-person spacewalking team that successfully captured
the stranded International Telecommunications Satellite. He also performed a
second EVA on STS-49 to evaluate space station construction techniques.  He has
logged over 311 hours of space flight.

     Jeffrey A. Hoffman, 49, will be Mission Specialist 3 (MS3) and serve as
one of the extravehicular activity crew members.  Selected as an astronaut in
January 1978, Hoffman considers Scarsdale, N.Y., his hometown and will be
making his fourth space flight.

     Hoffman graduated from Scarsdale High School, received a bachelor's degree
in astronomy from Amherst College, received a doctorate in astrophysics from
Harvard University and received a master's degree in materials science from
Rice University.

     Hoffman first flew on STS-51D in April 1985, a mission during which he
performed a spacewalk in an attempt to rescue a malfunctioning satellite.  He
next flew on STS-35 in December 1990.  Hoffman made his third space flight as
Payload Commander and mission specialist on STS-46 in July 1992.

     F.  Story Musgrave, 58, will be Mission Specialist 4 (MS4).  He also will
serve as Payload Commander and as a member of the extravehicular activity team.
Selected as an astronaut in August 1967, Musgrave considers Lexington, Ky., his
hometown and will be making his fifth space flight.

     Musgrave graduated from St. Mark's School, Southborough, Mass., in 1953;
received a bachelor's degree in mathematics and statistics from Syracuse
University in 1958; received a master's degree in operations analysis and
computer programming from the University of California at Los Angeles in 1959;
received a bachelor's degree in chemistry from Marietta College in 1960;
received a doctorate in medicine from Columbia University in 1964; received a
master's degree in physiology and biophysics from the University of Kentucky in
1966 and received a master's degree in literature from the University of
Houston in 1987.

     Musgrave flew as a mission specialist on STS-6 in April 1983, on
Spacelab-2 in August 1985 and on STS-33 in November 1989.  More recently, he
served aboard Space Shuttle Atlantis, STS-44 in November 1991.  He has logged
more than 598 hours in space.

     Claude Nicollier, 49, will be Mission Specialist 2 (MS2).  Under an
agreement with the European Space Agency and NASA, he was selected as an
astronaut in 1980.  Nicollier was born in Vevey, Switzerland, and will be
making his second space flight.

     Nicollier graduated from Gymnase de Lausanne, Lausanne, Switzerland,
received a bachelor's degree in physics from the University of Lausanne and
received a master's degree in astrophysics from the University of Geneva.
Nicollier first flew as a mission specialist on STS-46 in July 1992 and has
logged more than 191 hours in space.

     Kathryn C. Thornton, 41, will serve as Mission Specialist 1 (MS1) and as
one of the extravehicular activity crew members.  Selected as an astronaut in
May 1984, Thornton was born in Montgomery, Ala., and will be making her third
space flight.

     Thornton received a bachelor of science degree in physics from Auburn
University and a master of science degree and a doctorate in physics from the
University of Virginia. Thornton was awarded a NATO postdoctoral fellowship to
continue her research at the Max Planck Institute of Nuclear Physics in
Heidelberg, Germany.

     Thornton first flew as a mission specialist on STS-33 in November 1989.
On her second flight, she served on the crew of STS-49 in May 1992.  On STS-49,
Thornton performed an extravehicular activity to evaluate space station
assembly techniques.  She has logged over 333 hours in space.

STS-61 ACRONYMS AND ABBREVIATIONS

A-h        ampere-hour
ac        alternating current
ACE        actuator control electronics
ACP        astronaut control panel
AD        aperture door
AFD        aft flight deck
APS        antenna pointing system
AS        aft shroud
ATM        Apollo Telescope Mount
BAPS             berthing and positioning system
BCU        bus coupler unit
BOD        bright object detector
BOL        beginning of life
BOT        beginning of travel
BPRC              battery protection and reconditioning circuit
bps        bits per second
BPRC               battery protection and reconditioning circuit
BPSK            biphase shift keyed
BREC            body rate error check
C&DH            communication and data handling
C/C        configuration control
CC        cargo control
CCC        charge current controller
CCTV               closed-circuit television
CDI        command and data interface
CDU        command detector unit
CFRP               carbon-fiber-reinforced plastic
CGG        contingency gravity gradient
CIF        computer interface
CMD        command module
COM        communications module
CORU            candidate orbital replacement unit
CPM        central processor module
CPU        central processing unit
CSM        cargo systems manual
CSS        coarse Sun sensor
CU/SDF            control unit/science data formatter
D/A        digital to analog
DAK        double-aluminized Kapton
DBA        diode box assembly
dc        direct current
DCE        deployment control electronics
DIH        discrete input high
DISP        display
DIU        data interface unit
DIUI        DIU interface module
DMS        data management subsystem
DMU        data management unit
DPC        direct power converter
ECA        electronics control assembly
ECU        electronics control unit
ED        engineering data
EDB        external data bus
EMI        electromagnetic interference
EOL        end of life
EOT        end of travel
EP/TCE            electrical power/thermal control electronics
EPS        electrical power subsystem
ES        equipment section
ESA        European Space Agency
ESTR            engineering/science tape recorders
EU        electronics unit or expander unit
EVA        extravehicular activity
FEP        fluorinated ethylene-propylene
FGE        fine guidance electronics
FGS        fine guidance sensor
FHST            fixed head star tracker
FHSTI            FHST interface
FIFO        first in first out
FMDM            flexible multiplexer/demultiplexer
FOC        faint object camera
FOD        Flight Operations Directorate
FOS        faint object spectrograph
FOV        field-of-view
F/S        filter/shaper
FPA        focal plane assembly
FPDA            focal plane deck assembly
FPSA        focal plane structure assembly
FS        forward shell
FSS        flight support system
FWH               flexible wire harness
GEA        gimbal electronics assembly
GG        gravity gradient
GGM        GG mode
GPC        general purpose computer
GSE        ground support equipment
GSFC               Goddard Space Flight Center
GSTDN             ground spaceflight tracking and data network
HGA        high-gain antenna
HLD        high-level discrete
HOSC            Huntsville Operations Support Center
HRS        high resolution spectrograph
HSP        high-speed photometer
HST        Edwin P. Hubble Space Telescope
HWL        hardware load
I&C        instrumentation and communication
ICAPC              increased capacity adaptive payload carrier
ICU        instrumentation control unit
IDB        internal data bus
IMU        inertial measurement unit
IOU        input/output unit
IPCU        interface power control  unit
IR        infrared
JSC        Lyndon B. Johnson Space Center
KA        keep alive
kbps        kilo bits per second
KSC        Kennedy Space Center
LGA        low-gain antenna
LLD        low-level discrete
LMU        logical memory unit
LS        light shield
LMSC            Lockheed Missiles and Space Company

MA        multiaccess
Mbps               megabits per second
MCC        Mission Control Center
MCC-H              MCC - Houston
MCE        monitor and control electronics
MCU        mechanism control unit
MDB        multiplexed data bus
MET        mission elapsed time
MLD        manual locking device
MLI        multilayer insulation
MMS            multimission modular spacecraft
MOD        Mission Operations Directorate
MR        main ring
MRA        main ring assembly
MSB        most significant bit
MSFC               Marshall Space Flight Center
MSS        magnetic sensing system
MT        magnetic torquer
MTE        magnetic torquer electronics
MTP        master timing pulse
MTS        magnetic torquing system
MU        memory unit
N.m        Newton meter
NASA            National Aeronautics and Space Administration
NASCOM             NASA communications
NGT        NASCOM ground terminal
nm        nanometer
NSSC-I            NASA Standard Spacecraft Computer, Model I
OAO        Orbiting Astronomical Society
OCE        optical control subsystem
OCS        optical control subsystem
OCXO            ovencontrolled crystal oscillator
OLD        offload device
OPI        Orbiter payload interrogator
ORU        orbital replaceable unit
ORUC            ORU carrier
OSO        Orbiting Solar Observatory
OTA        optical telescope assembly
OV        orbital verification
P-E        Perkin-Elmer Corporation
PC        planetary camera
PCM        pulse-code modulation
PCS        pointing control subsystem
        pointing control system
PCU        power control unit
PDI        payload data interleaver
PDM        primary deployment mechanism
PDU        power distribution unit
PI        payload interrogator
PI/KUSP            PI/Ku-band signal processor
PIT        process interface table
PLBD            payload bay door
PLR        payload recorder
PM        primary mirror
PMA        primary mirror assembly
PMB        primary mirror baffle
PMT        photomultiplier tube
PMU        physical memory unit
PN        pseudorandom noise
POCC            Payload Operations Control Center
PRCS            primary react ion control system
PRI        primary
PRIPL            unregulated Orbiter power
PRLA               payload retention latch assembly
PROM               programmable read-only memory
PSEA            pointing and safe-mode electronics assembly
psi        pounds per square inch
psia        pounds per square inch absolute
PSP        payload signal processor
PSP/PI            PSP/payload interrogator
QD        quick disconnect
RBM        radial bay module
RED        redundant
RF        radio frequency
RFI        radio frequency interface
RGA        rate gyro assembly
RGAI        RGA interface
RIG        rate integrating gyro
RIU        remote interface unit
RMGA            retrieval mode gyro assembly
RM        remote module
RMS        remote manipulator system
ROM        read-only memory
RPA        reaction plate assembly
RSOC            Rockwell Shuttle Operations Company
RSU        rate sensor unit
RTC        real-time command
RWA        reaction wheel assembly
SA        solar array
SAD        SA drive
SADA            SA drive adapter
SADE            SA drive electronics
SADM            SA drive mechanism
SD        science data or scientific data
SDM        secondary deployment mechanism
SI        scientific instrument
SIC&DH            scientific instrument control and data handling
SIP        standard interface panel
SIPE        scientific instrument protective enclosure
SISS        SI support structure
S/M        safe mode
SM        secondary mirror
SMA        secondary mirror assembly
SMB        secondary mirror baffle
SMC        safemode computer
SMCH            standard mixed cargo harness
SMSA               secondary mirror subassembly
SM4        safe-mode utility
SOC        state-of-charge
SPA        solar panel assembly
SPC        stored program command
SPG        single-point ground
SQPSK             staggered quadiphased, shift-keyed
SS        safing system
SSA        S-band single-access
SSC        Science Support Center
SSE        space support equipment
SSM        support systems module
SSM-ES            SSM equipment shelf
SSP        standard switch panel
SSS        star selector servo
STACC              standard telemetry and command components
STDN              space flight tracking and data network
STINT            standard interface
STOCC            Space Telescope Operations Control Center
STS        Space Transportation System
STSCI            Space Telescope Science Institute
TAG        two-axis gimbal
TBD        to  be determined
TCE        thermal control electronics
TCS        thermal control subsystem
TCXO               temperature controlled crystal oscillator
TDRS               tracking and data relay satellite
TDRSS            TDRS system
TFC        TLM format control
TIM        timing interface module
TLM        telemetry
TRI        tape recorder interface
TTL        transistor-to-transistor logic
UDM        umbilical disconnect mechanism
ULE        ultralow expansion
URM        umbilical retraction mechanism
UV        ultraviolet
VATA               Vehicle Assembly and Test Area
VCO        voltage controlled oscillator
VSS        vehicle support software
VSWR            voltage standing wave radio
WF/PC            wide field/planetary camera
WFC        wide field camera
WSGT            White Sands Ground Terminal

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