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he Hubble Space Telescope (HST) is thefirst observatory designed for extensivemaintenance and refurbishment in

orbit. While other U.S. spacecraft have beenretrieved or repaired by astronauts, none wasso thoroughly designed for orbital servicing asHST. Its science instruments and many othercomponents were designed as OrbitalReplacement Units (ORU) – modular in con-struction with standardized fittings and acces-sible to spacewalking astronauts. Features suchas handrails and foot restraints are built intothe Telescope to help astronauts perform ser-vicing tasks in the Shuttle cargo bay as theyorbit Earth at 17,500 mph.

For Servicing Mission 3A (SM3A), the Discoverycargo bay is equipped with several devices tohelp the astronauts. The Flight SupportSystem (FSS) will berth and rotate theTelescope. Large, specially designed equip-ment containers house the ORUs. Astronautscan work and be maneuvered as needed fromthe Shuttle robot arm.

SM3A will benefit from lessons learned onNASA’s previous on-orbit servicing missions,ranging from the 1984 Solar Maximum repairmission to the 1993 HST First ServicingMission (SM1) and the 1997 Second ServicingMission (SM2). NASA has incorporated theselessons in detailed planning and training ses-sions for astronauts Curtis Brown, Jr., ScottKelly, Jean-François Clervoy, Steven Smith,John Grunsfeld, Michael Foale, and ClaudeNicollier. All of NASA’s planning and theastronauts’ skills will be put to the test duringthe SM3A mission in 1999. Four extravehicularactivity (EVA) days are scheduled for theservicing.

2.1 Reasons for Orbital Servicing

The Hubble Telescope is a national asset and aninvaluable international scientific resource thathas revolutionized modern astronomy. Toachieve its full potential, HST will continue toconduct extensive, integrated scientific obser-vations, including follow-up work on its manydiscoveries.

Although the Telescope has numerous redun-dant parts and safemode systems, such a com-plex spacecraft cannot be designed withsufficient backups to handle every contingencylikely to occur during a 20-year mission.Orbital servicing is the key to keeping Hubblein operating condition. NASA’s orbital servic-ing plans address three primary maintenancescenarios:

• Incorporating technological advances intothe science instruments and ORUs

• Normal degradation of components• Random equipment failure or malfunction.

Technological Advances. Throughout theTelescope’s 20-year life, scientists and engineerswill upgrade the science instruments. Forexample, when Hubble was launched in 1990, itwas equipped with the Goddard HighResolution Spectrograph and the Faint ObjectSpectrograph. A second-generation instrument,the Space Telescope Imaging Spectrograph,took over the function of those two instruments– and added considerable new capability –when it was installed during the SecondServicing Mission in February 1997. This leftopen a slot for the Near Infrared Camera andMulti-Object Spectrometer (NICMOS), whichexpanded the Telescope’s vision into the

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infrared region of the spectrum. Additionally,on SM2 a new Solid State Recorder (SSR)replaced an Engineering/Science TapeRecorder (E/STR).

Component Degradation. Servicing plans takeinto account the need for routine replacementof some items, for example, restoring HST sys-tem redundancy and limited-life items such astape recorders and gyroscopes.

Equipment Failure. Given the enormous sci-entific potential of the Telescope – and theinvestment in designing, developing, building,and putting it into orbit – NASA must be ableto correct unforeseen problems that arise fromrandom equipment failures or malfunctions.The Space Shuttle program provides a provensystem for transporting astronauts to theTelescope fully trained for its on-orbit servicing.

Originally, planners considered using theShuttle to return the Telescope to Earthapproximately every five years for mainte-nance. However, the idea was rejected for bothtechnical and economic reasons. ReturningHubble to Earth would entail a significantlyhigher risk of contaminating or damaging del-icate components. Ground servicing wouldrequire an expensive clean room and supportfacilities, including a large engineering staff,and the Telescope would be out of actionfor a year or more – a long time to suspendscientific observations.

Shuttle astronauts can accomplish mostmaintenance and refurbishment within a10-day on-orbit mission – with only a briefinterruption to scientific operations andwithout the additional facilities and staffneeded for ground servicing.

2.2 Orbital Replacement Units

Advantages of ORUs include modularity, stan-dardization, and accessibility.

Modularity. Engineers studied various tech-nical and human factors criteria to simplifyTelescope maintenance. Due to the limitedtime available for repairs and the astronauts’limited visibility, mobility, and dexterity in theEVA environment, designers simplified themaintenance tasks by planning entire compo-nents for replacement.

The modular ORU concept is key to success-fully servicing the Telescope on orbit. ORUsare self-contained boxes installed and removedusing fasteners and connectors. They rangefrom small fuses to phone-booth-sized scienceinstruments weighing more than 700 lb (318 kg).Figure 2-1 shows the ORUs for SM3A.

Standardization. Standardized bolts and con-nectors also simplify on-orbit repairs. Captivebolts with 7/16-in., double-height hex headshold many ORU components in place. Toremove or install the bolts, astronauts needonly a 7/16-in. socket fitted to a power tool ormanual wrench. Standardization limits thenumber of crew aids and tools.

Some ORUs do not contain these fasteners.When the maintenance philosophy changedfrom Earth-return to on-orbit-only servicing,other components were selected as replaceableunits after their design had matured. Thisadded a greater variety of fasteners to the ser-vicing requirements, including non-captive5/16-in.-head bolts and connectors withoutwing tabs. Despite these exceptions, the highlevel of standardization among units reduces

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the number of tools needed for the servicingmission and simplifies astronaut training.

Accessibility. To be serviced in space,Telescope components must be seen andreached by an astronaut in a bulky pressuresuit, or they must be within range of the appro-priate tool. Therefore, most ORUs are mountedin equipment bays around the perimeter of thespacecraft. To access these units, astronautssimply open a large door that covers the appro-priate bay.

Handrails, foot restraint sockets, tether attach-ments, and other crew aids are essential to effi-cient, safe on-orbit servicing. In anticipation ofservicing missions, 31 foot restraint socketsand 225 ft of handrails were designed into the

Telescope. The foot restraint sockets andhandrails greatly increase the mobility and sta-bility of EVA astronauts, giving them safeworksites conveniently located near ORUs.

Crew aids such as portable lights, special tools,installation guiderails, handholds, and port-able foot restraints (PFR) also ease servicing ofthe telescope components. In addition, footrestraints, translation aids and handrails arebuilt into various equipment and instrumentcarriers specific to each servicing mission.

2.3 Shuttle Support Equipment

To assist the astronauts in servicing theTelescope, Discovery will carry into orbit severalthousand pounds of hardware and Space

Fig. 2-1 Hubble Space Telescope Servicing Mission 3A Orbital Replacement Units

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Support Equipment (SSE), including theRemote Manipulator System (RMS), FSS, andORU Carrier (ORUC).

2.3.1 Remote Manipulator System

The Discovery RMS, also known as the roboticarm, will be used extensively during SM3A.The astronaut operating this device frominside the cabin is designated intravehicularactivity (IVA) crew member. The RMS will beused to:

• Capture, berth, and release the Telescope• Transport new components, instruments,

and EVA astronauts between worksites• Provide a temporary work platform for one

or both EVA astronauts.

2.3.2 Space Support Equipment

Ground crews will install two major assem-blies essential for SM3A – the FSS and ORUC –in Discovery’s cargo bay. Figure 2-2 shows acargo bay view of these assemblies.

Fig. 2-2 Servicing Mission 3A Payload Bay configuration

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Flight Support System. The FSS is a mainte-nance platform used to berth the HST in thecargo bay after the Discovery crew has ren-dezvoused with and captured the Telescope(see Fig. 2-3). The platform was adapted fromthe FSS first used during the 1984 SolarMaximum repair mission. It has a U-shapedcradle that spans the rear of the cargo bay. Acircular berthing ring with three latchessecures the Telescope to the cradle. The berthingring can rotate the Telescope almost 360 degrees(176 degrees clockwise or counterclockwisefrom its null position) to give EVA astronautsaccess to every side of the Telescope.

The FSS also pivots to lower or raise theTelescope as required for servicing or reboost-ing. The FSS’s umbilical cable provides powerfrom Discovery to maintain thermal control ofthe Telescope and permits ground engineers totest and monitor Telescope systems during theservicing mission.

2.3.3 Orbital Replacement UnitCarrier

The ORUC is centered in Discovery’s cargo bay.A Spacelab pallet modified with a shelf, it hasprovisions for safe transport of ORUs to andfrom orbit (see Fig. 2-4). In the SM3A configu-ration:

• The Fine Guidance Sensor (FGS) #2 is storedin the Fine Guidance Sensor ScientificInstrument Protective Enclosure (FSIPE).

• The Large ORU Protective Enclosure(LOPE) contains the Advanced Computerand two Y-harnesses (going up), two spareVoltage/Temperature Improvement Kits(VIK), and the DF-224 computer and co-processor (returning from orbit).

• The Contingency ORU Protective Enclosure(COPE) houses three Rate Sensor Units(RSU), the Solid State Recorder (SSR) (goingup), the S-band Single Access Transmitter

Fig 2-3 Flight Support System configurationK9322_203

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(SSAT), the Engineering/Science TapeRecorder (E/STR) (coming back), and addi-tional harnesses. Contingency hardwareincluding the Electronics Control Unit(ECU), the spare Optics Control ElectronicsEnhancement Kit (OCE/EK), and the PowerDistribution Unit (PDU) connector coversare stowed in the COPE.

• Connector converters for the AdvancedComputer are on the COPE lid.

• The Axial Scientific Instrument ProtectiveEnclosure (ASIPE) shelf contains the spareAdvanced Computer, the spare RSU, sixMulti-Layer Insulation (MLI) patches (twolarge and four small), seven Shell/ShieldReplacement Fabrics (SSRFs), and six SSRFrib clamps.

• The New Outer Blanket Layer (NOBL)Protective Enclosure (NPE) contains thenew protective coverings to be installed onthe Telescope equipment bay doors.

• The Auxiliary Transport Module (ATM)houses MLI Recovery Bags, the DataManagement Unit (DMU)/AdvancedComputer contingency cables, a debris bag,and a spare SSAT coaxial cable.

The protective enclosures, their heaters, andthermal insulation control the temperature ofthe new ORUs and provide an environmentequivalent to that inside the Telescope. Struts,springs, and foam between the enclosures andthe pallet protect the ORUs from the loadsgenerated at liftoff and during Earth return.

Fig. 2-4 Orbital Replacement Unit Carrier

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2.4 Astronaut Roles and Training

To prepare for SM3A, the seven-memberDiscovery crew trained extensively at NASA’sJohnson Space Center (JSC) in Houston, Texas,and Goddard Space Flight Center (GSFC) inGreenbelt, Maryland.

Although there has been extensive cross train-ing, each crewmember also has trained forspecific tasks. Training for MissionCommander Brown and Pilot Kelly focusedon rendezvous and proximity operations,such as retrieval and deployment of theTelescope. The two astronauts rehearsed theseoperations using JSC’s Shuttle MissionSimulator, a computer-supported trainingsystem. In addition, they received IVA train-ing – helping the EVA astronauts into suitsand monitoring their activities outside theDiscovery cabin.

The five Mission Specialists also receivedspecific training, starting with classroominstruction on the various ORUs, tools andcrew aids, Space Support Equipment (SSE)such as the RMS (the robotic arm), and theFSS. Principal operator of the robotic arm isMission Specialist Clervoy, who also per-forms IVA duties. The alternate operatorsare mission specialists Claude Nicollier andJohn Grunsfeld.

Clervoy trained specifically for capture andredeployment of the Telescope, rotation andpivoting of the Telescope on the FSS, and relatedcontingencies. These operations were simulatedwith JSC’s Manipulator Development Facility,which includes a mockup of the robotic armand a suspended helium balloon with dimen-sions and grapple fixtures similar to those onthe Telescope. RMS training also took place at

JSC’s Neutral Buoyancy Laboratory (NBL),enabling the RMS operator and alternates towork with individual team members. Forhands-on HST servicing, EVA crewmemberswork in teams of two in the cargo bay.Astronauts Smith, Grunsfeld, Foale, andNicolier logged many days of training for thisimportant role in the NBL, a 40-ft (12-m)-deepwater tank (see Fig. 2-5).

In the NBL, pressure-suited astronauts andtheir equipment are made neutrally buoy-ant, a condition that simulates weightless-ness. Underwater mockups of the Telescope,FSS, ORUs, ORUC, RMS, and the Shuttlecargo bay enabled the astronauts to practiceentire EVA servicing. Such training activi-ties help the astronauts efficiently use thelimited number of days (four) and duration(six hours) of each EVA period during theservicing mission.

Other training aids at JSC helped recreateorbital conditions for the Discovery astronauts.In the weightlessness of space, the tiniestmovement can set instruments weighing sev-eral hundred pounds, such as FGS #2, intomotion.

To simulate the delicate on-orbit conditions,models of the instruments are placed on padsabove a stainless steel floor and floated on athin layer of pressurized gas. This allowscrewmembers to practice carefully nudgingthe instruments into their proper locations.

Astronauts also used virtual reality technolo-gies in their training. This kind of ultrarealisticsimulation enabled the astronauts to “see”themselves next to the Telescope as their part-ners maneuver them into position with therobotic arm.

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Fig. 2-5 Neutral Buoyancy Laboratory at NASA Johnson Space Center

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2.5 Extravehicular Crew Aids andTools

Astronauts servicing HST use three differentkinds of foot restraints to counteract theirweightless environment. When anchored in aManipulator Foot Restraint (MFR), an astronautcan be transported from one worksite to the nextwith the RMS. Using either the STS or HST PFR,an astronaut establishes a stable worksite bymounting the restraint to any of 31 differentreceptacles strategically placed on the Telescopeor 16 receptacles on the ORUC and the FSS.

In addition to foot restraints, EVA astronautshave more than 150 tools and crew aids at theirdisposal. Some of these are standard itemsfrom the Shuttle’s toolbox, while others areunique to this servicing mission. All tools aredesigned to be used in a weightless environmentby astronauts wearing pressurized gloves.

The most commonly used ORU fasteners arethose with 7/16-in., double-height hex heads.These bolts are used with three different kindsof fittings: J-hooks, captive fasteners, and key-hole fasteners. To replace a unit, the astronautsuse a 7/16-in. extension socket on a powered ormanual ratchet wrench. Extensions up to 2 ftlong are available to extend an astronaut’sreach. Multi-setting torque-limiters preventover-tightening of fasteners or latch systems.

For units with bolts or screws that are not cap-tive in the ORU frame, astronauts use tools fit-ted with socket capture fittings – and speciallydesigned capture tools – so that nothing floatsaway in the weightless space environment. Togrip fasteners in hard-to-reach areas, the crewcan use wobble sockets.

Some ORU electrical connectors require specialtools, such as a torque tool to loosen coaxial

connectors. If connectors have no wing tabs,astronauts use another special tool to get a firmhold on the rotating ring of the connector.

Portable handles have been attached to manylarger ORUs to facilitate removal or installa-tion. Other tools and crew aids used during theservicing mission are tool caddies (carryingaids), tethers, transfer bags, and protective cov-ers for the Low Gain Antenna (LGA).

When astronauts work within the Telescope’saft shroud area, they must guard against opticscontamination by using special tools that willnot outgas or shed particulate matter. All toolsare certified to meet this requirement.

2.6 Astronauts of the ServicingMission 3A

NASA carefully selected and trained the SM3ASTS-103 crew (see Fig. 2-6). Their unique set ofexperiences and capabilities makes them emi-nently qualified for this challenging assign-ment. Brief biographies of the STS-103astronauts follow.

Curtis L. Brown, Jr., NASA Astronaut(Lieutenant Colonel, USAF). Curtis Brown ofElizabethtown, North Carolina, is commanderof SM3A. He received a bachelor of sciencedegree in electrical engineering from the AirForce Academy in 1978. His career highlightsinclude: 1992 – pilot of STS-47 Spacelab-J, aneight-day cooperative mission between theUnited States and Japan; 1994 – pilot of STS-66,the Atmospheric Laboratory for Applicationsand Science-3 (ATLAS-3) mission; 1996 – pilotof STS-77, whose crew performed a recordnumber of rendezvous sequences (one with aSPARTAN satellite and three with a deployedSatellite Test Unit) and approximately 21 hoursof formation flying in close proximity of the

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satellites; 1997 – commander of STS-85, a 12-day mission that included deployment andretrieval of the CRISTA-SPAS payload; 1998 –commander of STS-95, a nine-day mission dur-ing which the crew supported a variety ofresearch payloads including the Hubble SpaceTelescope Orbital Systems Test Platform anddeployment of the Spartan solar-observingspacecraft.

Scott J. Kelly, NASA Astronaut (LieutenantCommander, USN). Scott Kelly, Discovery piloton SM3A, is from Orange, New Jersey. Hereceived a bachelor of science degree in electri-cal engineering from the State University ofNew York Maritime College in 1987 and a mas-ter of science degree in aviation systems fromthe University of Tennessee, Knoxville, in 1996.Kelly became a naval aviator in 1989 andserved in the North Atlantic, MediterraneanSea, Red Sea and Persian Gulf. He graduatedfrom the U.S. Naval Test Pilot School in 1994,then worked as a test pilot, logging over 2,000flight hours in more than 30 different aircraft.After completing two years of training andevaluation at Johnson Space Center in 1998, hequalified for flight assignment as a pilot. Beforehis selection for the SM3A crew, Kelly per-formed technical duties in the Astronaut OfficeSpacecraft Systems/Operations Branch.

Jean-François Clervoy, ESA Astronaut. Jean-François Clervoy, the RMS operator on SM3A,is from Toulouse, France. Clervoy received hisbaccalauréat from Collège Militaire de SaintCyr l’ Ecole in 1976 and graduated from EcolePolytechnique, Paris, in 1981. He was selectedas a French astronaut in 1985 and became aflight test engineer in 1987. Clervoy served aschief test director of the Parabolic FlightProgram at the Flight Test Center, Brétigny-sur-Orge, where he was responsible for testing andqualifying the Caravelle aircraft for micrograv-

ity. He also worked at the Hermes Crew Office,Toulouse, supporting the European MannedSpace Programs. Clervoy trained in Star City,Moscow, on the Soyuz and Mir systems in1991. He was selected for the astronaut corps ofthe European Space Agency (ESA) in 1992.After a year of training at the Johnson SpaceCenter, he qualified as a mission specialist forSpace Shuttle flights. Clervoy flew twiceaboard Space Shuttle Atlantis and has loggedover 483 hours in space. He served as a missionspecialist on STS-66 in 1994 and as the payloadcommander on STS-84 in 1997.

Steven L. Smith, NASA Astronaut. StevenSmith is payload commander and EVAcrewmember (designated EV1 on EVA Days 1& 3). He was born in Phoenix, Arizona, butconsiders San Jose, California, to be his home-town. He received both bachelor and master ofscience degrees in electrical engineering and amaster’s degree in business administrationfrom Stanford University. Smith served as amission specialist aboard the Space ShuttleEndeavour on STS-68 in 1994. His responsibili-ties during the 11-day flight included Shuttlesystems and Space Radar Lab 2 (the flight’sprimary payload). Smith flew as an EVA crewmember on STS-82, the HST Second ServicingMission, in 1997. He made two 6-hour spacewalks while installing new science instrumentsand upgraded technology. From November1994 until March 1996, Smith was assigned tothe astronaut support team at Kennedy SpaceCenter. The team was responsible for SpaceShuttle prelaunch vehicle checkout, crewingress and strap-in, and crew egress postlanding.

John M. Grunsfeld, Ph.D., NASA Astronaut.John Grunsfeld is an astronomer and an EVAcrewmember (EV2 on EVA Days 1 & 3) on theSM3A mission. He was born Chicago, Illinois.

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Grunsfeld received a bachelor of science degreein physics from the Massachusetts Institute ofTechnology in 1980 and a master of sciencedegree and a doctor of philosophy degree inphysics from the University of Chicago in 1984and 1988, respectively. Grunsfeld reported to theJohnson Space Center in 1992 for a year of train-ing and became qualified for flight selection as amission specialist. A veteran of two spaceflights, he has logged over 644 hours in space.On his first mission, STS-67 in March 1995,Grunsfeld and the crew conducted observationsaround the clock to study the far ultravioletspectra of faint astronomical objects and thepolarization of ultraviolet light coming from hotstars and distant galaxies. Grunsfeld flew onSTS-81 in 1991 on the fifth mission to dock withRussia’s Space Station Mir and the second toexchange U.S. astronauts.

C. Michael Foale, Ph.D., NASA Astronaut.Michael Foale is an EVA crewmember (EV1 onEVA Days 2 & 4) on SM3. He was born inLouth, England, but considers Cambridge,England, to be his hometown. He attended theUniversity of Cambridge, Queens’ College,receiving a bachelor of arts degree in physics,with first-class honors, in 1978. He completedhis doctorate in Laboratory Astrophysics atCambridge in 1982. NASA selected Foale as anastronaut candidate in 1987 and he completedastronaut training and evaluation in 1988. Aveteran of four space flights, Foale has loggedover 160 days in space including 10-1/2 hoursof EVA. He was a mission specialist on STS-45in 1992 and STS-56 in 1993, the first two ATLASmissions to address the atmosphere and itsinteraction with the Sun. He was a member ofthe first Shuttle crew (STS-63) to rendezvouswith Russia’s Mir Space Station in 1995. Foalespent four months aboard Mir in 1997, con-ducting various science experiments and help-ing the crew resolve and repair numerous

malfunctioning systems. He arrived May 17 onSpace Shuttle Atlantis (STS-84) and returnedOctober 6, also on Atlantis (STS-86).

Claude Nicollier, ESA Astronaut. ClaudeNicollier is an EVA crewmember (EV2 on EVADays 2 & 4) on SM3A. A native of Vevey,Switzerland, he received a bachelor of sciencedegree in physics from the University ofLausanne in 1970 and a master of sciencedegree in astrophysics from the University ofGeneva in 1975. He became a Swiss Air Forcepilot in 1966, an airline pilot in 1974, and a testpilot in 1988. In July 1978 ESA selected Nicollieras a member of the first group of Europeanastronauts. Under agreement between ESA andNASA, he joined the NASA astronaut candi-dates selected in 1980 for training as a missionspecialist. A veteran of three space flights,Nicollier has logged more than 828 hours inspace. He participated in the deployment of theEuropean Retrievable Carrier (EURECA) sci-ence platform on STS-46 in 1992. He was theRMS operator on STS-61 in 1993, the first HSTservicing and repair mission. He also served asa mission specialist on STS-75 aboard Columbiain 1996 – the reflight of the Tethered SatelliteSystem and the third flight of the United StatesMicrogravity Payload.

2.7 Servicing Mission Activities

After Discovery berths the Hubble SpaceTelescope in Fall of 1999, the seven-personcrew will begin an ambitious servicing mis-sion. Four days of EVA tasks are scheduled.Each EVA session is scheduled for six hours.

2.7.1 Rendezvous With the HubbleSpace Telescope

Discovery will rendezvous with Hubble in orbit320 nautical miles (512 km) above the Earth.

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Prior to approach, in concert with the SpaceTelescope Operations Control Center (STOCC)at GSFC, Mission Control will command HSTto stow the High Gain Antennas (HGA) andclose the aperture door. As Discoveryapproaches the Telescope, Commander Brownwill control the thrusters to avoid contaminat-ing HST with propulsion residue. During thisapproach the Shuttle crew will be in close con-tact with Mission Control at JSC.

As the distance between Discovery and HSTdecreases to approximately 200 ft (60 m), theSTOCC ground crew will command HST toperform a final roll maneuver to position itselffor grappling. The Solar Arrays (SA) willremain fully deployed parallel to the opticalaxis of the Telescope.

When Discovery and HST achieve the properposition, Mission Specialist Clervoy will oper-ate the robotic arm to grapple the Telescope.Using a camera mounted at the berthing ring ofthe FSS platform in the cargo bay, he willmaneuver HST to the FSS, where the Telescopewill be berthed and latched.

Once the Telescope is secured, the crew willremotely engage the electrical umbilical andswitch Hubble from internal power to externalpower from Discovery. Pilot Kelly also willmaneuver the Shuttle so that the SAs face theSun to recharge the Telescope’s six onboardnickel-hydrogen (NiH2) batteries.

2.7.2 Extravehicular ServicingActivities – Day by Day

Figure 2-7 shows the schedule for four plannedsix-hour EVA servicing periods. These timespans are planning estimates; the schedule will bemodified as needed as the mission progresses.

During the EVAs, HST will be vertical relativeto Discovery’s cargo bay. Four EVA mission spe-cialists will work in two-person teams on alter-nate days. One team is Steve Smith and JohnGrunsfeld; the other is Mike Foale and ClaudeNicollier.

One astronaut, designated EV1, accomplishesprimarily the free-floating portions of the EVAtasks. He can operate from a PFR or while freefloating. The other astronaut, EV2, works pri-marily from an MFR mounted on Discovery’srobotic arm (RMS), removing and installing theORUs on the Hubble. EV1 assists EV2 inremoval of the ORUs and installation of thereplaced units in the SM3A carriers.

To reduce crew fatigue, EVA crewmembersswap places once during each EVA day; thefree floater goes to the RMS MFR and viceversa. Inside Discovery’s aft flight deck, the off-shift EVA crewmembers and the designatedRMS operator assist the EVA team by readingout procedures and operating the RMS.

At the beginning of EVA Day 1 (the fourth dayof the mission), the first team of EVA astronautssuit up and pass through the Discovery airlockinto the cargo bay. To prevent themselves fromaccidentally floating off, they attach safety teth-ers to a cable running along the cargo bay sills.EV1 accomplishes a variety of specific tasks toprepare for that day’s EVA servicing activities.These include removing the MFR from itsstowage location and installing it on the RMSgrapple fixture, installing the Low GainAntenna Protective Cover (LGA PC), deploy-ing the Translation Aids (TA), and removingthe Berthing and Positioning System (BAPS)Support Post from its stowage location andinstalling it on the FSS with the assistance ofEV2.

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Meanwhile, EV2 brings out of the airlock theCrew Aids and Tools (CATs) that will beattached to the handrails of the RMS. Heinstalls the CATs handrail to the RMS and thecolor television camera (CTVC) on the MFR.The IVA RMS operator then moves EV2 to theBAPS Support Post (BSP) installation worksiteto install the BSP forward end on the BAPS.

EVA Day 1: Change out three RSUs. Removecaps and open the NICMOS “Coolant In” and“Coolant Out” valves. Install VIK on HSTbatteries.

During EVA Day 1, Smith and Grunsfeld arescheduled to replace three new RSUs in the

Telescope. They will also remove caps from theNICMOS “Coolant In” and “Coolant Out”valves. Any ice contained within those valveswill sublimate in the vacuum of space and facil-itate installation of a replacement cooler forNICMOS on SM3B. Additionally, the astronautswill install VIKs on the six batteries aboard HST.

Once in the payload bay, the astronauts beginthe initial setup, which includes installation ofthe LGA protective cover, TA deployments,and installation and deployment of the BSP.

The BSP is required to dampen the vibrationthat the servicing activities will induce into thedeployed SAs. Prior to the BSP installation on

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Priority Task Times (stand-alone)

1. RSUs (RSU-1, -2, -3)2. VIK3. Advanced Computer4. FGS (FGS-2)5. SSAT (SSAT-2)

6. SSR (ESTR-3)7. Bay 5-10 MLI Repair8. NICMOS valves open

1:55 ea1:101:503:001:30

1:152:25 total 0:20

3:07 OT#1. FS/LS MLI RepairOT#2. Handrail Covers Bays A & JOT#3. ASLR for +V2 Doors

Required Setup

Optional Tasks & Priorities

Task Times1:00 (1st day)0:15 (nth day)

0:30 (nth day)1:00 (last day)

Setup

Closeup

6-hour EVA period

EVA Day 1

EVA Day 2

EVA Day 3

EVA Day 4

Includes BAPS Post installationAft Shroud Door latch contingencycrew change positions in Manipulator Foot RestraintHigh Gain Antenna deployment

VIKClose0:30

Close0:30

RSU 1, 2 & 3Setup°1:00

ComputerSet:15

Sun protect attitude

Sun protect attitude

MF

R

MF

R

AS

D

Val

ves

Computer FGS2

r rr@305° r@30° r@-V3; p@90°(±)@0°(±)-30°→0°(±)SA@-30°

prp

(±) 0°-30°SA

FSS

SA

FSS

A

FSS

SA

FSS

(±)SA@20°p@90°; r@+V3

(±) 0°→20°

(±)SA@-20°p@90°; r@+V3p@90°; r@-V2 r

(±)SA@0° (±) 0°→100°

p@90°; r@-V3p@85°; r@-V3p:90°→85°(±) 100°→0°

(+) -20°→0°

(±) 20°→0°

(±) 0°→90°

r:-V3→-V2

(-):0°→15°→-20°

p

Goddard Space Flight Center

° =ASD =MFR =HGA =

SSRF NOBL FGS-2 SA slew FSS pivot

FSS rotationberthing position

HST-V3RSU VIK

Valves Open

OCEK Computer

+V345°

90°90°

0° 0°0°

-45°-V3

+V2-V2

Hubble Space TelescopeFlight Systems and Servicing Project

OT#1 MLIFS/LS 5, 6 & 7

Set:15 H

GA Closeout

1:00OT #2&/or #3

OT#1 MLIFS/LS 1 & 2

OT#1 MLIFS/LS 3 & 4

SSA XmtrSet:15 SSR

MLI RepairBays 5, 6, 7, 8, 9, 10

Close0:30OCE

MF

R

Fig. 2-7 Detailed schedule of extravehicular activities and SA and FSS positions during SM3A

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EVA Day 1, the IVA team commands the HSTto an 85-degree pivot angle. The two centerpush-in-pull out (PIP) pins are installed eachday and removed each night in the event thatthe Shuttle must make an emergency return toEarth. Steve Smith (EV1) removes the BSP fromits stowage position in the cradle of the FSSand hands the forward end to John Grunsfeld(EV2) who installs his end to the BAPS ringwith a PIP pin. Smith then installs the aft endof the BSP to the FSS cradle with a PIP pin.Finally the BSP is commanded to its 90-degreelimit and the two center PIP pins are installed.

After the BSP is installed and other initial setuptasks are completed, the crew starts the specifictasks for the RSU change-outs. First Smith,who is free floating, retrieves the STS PFR andArticulating Socket and temporarily stowsthem at the aft ORUC. Smith and Grunsfeld (inthe MFR), move to the COPE to retrieve thereplacement RSU-2. To accomplish theremoval, they open three COPE T-handle lidlatches and the COPE lid, then release thetransport module T-handle latch and open it.They remove the replacement RSU-2 and stowit in the ORU transfer bag. Next they close thetransport module and the COPE lid andengage two T-handle latches.

The astronauts then translate to the aft shroud.They inspect the area for excessive particulatesor debris and when satisfied that the area isclear, Smith and Grunsfeld open the HST –V3aft shroud doors by retracting two Fixed HeadStar Tracker (FHST) seals and disengaging fourdoor latches.

Smith then installs the PFR and articulatingsocket in the HST aft shroud and ingresses.Smith and Grunsfeld remove the old RSU-2 bydemating two wing tab connectors and disen-gaging three 7/16-in. hex-head captive spring-

loaded fasteners. Smith and Grunsfeld removethe RSU-2 replacement from the ORU transferbag. They remove the two connector caps andinstall the replacement RSU-2 in HST, engagingthree fasteners and mating the two connectors(see Fig. 2-8). Finally, they replace the old RSU-2in the ORU transfer bag.

Smith steps out of the PFR, reconfigures it forthe RSU-3 position, and gets back into the PFR.Meanwhile, Grunsfeld maneuvers to the COPEand opens the lid, stowing the old RSU-2 andretrieving the RSU-3 replacement. He stows itin the ORU transfer bag, then temporarily clos-es the COPE lid (two latches) and maneuversback to the aft shroud.

Smith and Grunsfeld remove the old RSU-3 bydemating two wing tab connectors and disen-gaging three 7/16-in. hex captive spring-loaded fasteners. They then remove thereplacement RSU-3 from the ORU transfer bagand install it, first removing the two connectorcaps, then seating it in HST. They engage threefasteners, mate the two connectors and placethe old RSU-3 in the ORU transfer bag.

Smith exits the PFR and reinstalls it in the aftshroud door closing position. Grunsfeld per-forms a video close-out on the two newlyinstalled RSUs. He then maneuvers to the COPEand stows RSU-3. He retrieves the replacementRSU-1 and stows it in the ORU transfer bag. Hetemporarily closes the COPE lid (one latch)and maneuvers back to the aft shroud.

Grunsfeld, on the MFR at the end of the RMS,removes the old RSU-1 by demating two wingtab connectors and disengaging three 7/16-in.hex captive spring-loaded fasteners. Theyinstall the replacement RSU-1 by removing thetwo connector caps, removing the replacementfrom the ORU transfer bag, seating it in HST

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and engaging three fasteners, and mating twoconnectors. After the old RSU-1 is stowed inthe ORU transfer bag, Grunsfeld performs thereplacement RSU-1 video close-out.

While positioned at the Aft Shroud, Smith andGrunsfeld then perform the NICMOS valvereconfiguration. They remove two “CoolantIn” and “Coolant Out” bayonet caps and openthe “Coolant In” and “Coolant Out” valves.Grunsfeld performs the NICMOS valve recon-figuration video close-out.

Grunsfeld partially closes the –V3 AftShroud doors as Smith ingresses the PFR.With Smith’s assistance, Grunsfeld closes theleft and right doors, engages the four doorlatches, checks the door seals, and extends thetwo FHST light seals. Smith egresses thePFR/Articulating Socket, removing it fromHST and restowing it in cargo bay. Grunsfeldmaneuvers to the COPE and stows the oldRSU-1 in the transport module, closes thetransport module lid, then fully closes theCOPE lid, engaging all three latches.

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Fig. 2-8 Change-out of Rate Sensor UnitK9322_208

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Smith and Grunsfeld now prepare to installVIKs on the HST batteries. Smith takesGrunsfeld’s place on the MFR and Grunsfeldbecomes the free floater after the MFR swap.

Grunsfeld translates to airlock, retrieves theVIK Caddy, translates to Bay 3, and transfersthe VIK Caddy to Smith. Smith (in the MFR)opens the Bay 3 door by disengaging six

J-hooks. Grunsfeld retrieves the handrail covercaddy, inspects the handrails around Bays 2and 3, and installs the handrail covers ifneeded. Smith demates three Bay 3 battery con-nectors (one at a time) and installs a VIK in-linewith each battery connector (see Fig. 2-9).Smith performs the Bay 3 VIK video close-out,closes the door, and engages the six doorJ-hooks.

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Fig. 2-9 Voltage/Temperature Improvement Kit installationK9329_209

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Smith then opens Bay 2 door by disengagingsix J-hooks. He demates three Bay 2 batteryconnectors (one at a time) and installs a VIK in-line with each battery connector. He performsthe Bay 2 VIK video close-out, closes the door,engages the six door J-hooks, and stows theVIK Caddy on the MFR.

For the daily close-out, Grunsfeld removes thecenter pins on the BSP, inspects the FSS mainumbilical, and retracts the TAs while Smithprepares the CATs installed on the MFRhandrail for return into the airlock.Additionally, Smith releases the MFR safetytether from the grapple fixture for contingencyEarth return and releases the lower CTVCcable. After the completion of EVA Day 1, bothastronauts return to the airlock with the Day 1CATs installed on the MFR handrail.

EVA Day 2: Replace DF-224 computer withAdvanced Computer and install Bay 1 NOBL.Change out FGS-2.

During EVA Day 2, EVA astronauts Nicollier(EV1) and Foale (EV2) are scheduled to replaceHST’s DF-224 computer with a faster, morepowerful unit called the Advanced Computer.They will also change out a degraded FGS inposition number 2 (see Fig. 2-10).

Fewer daily setup tasks are required for EVADay 2 than for EVA Day 1. Foale exits the air-lock with the EVA Day 2 required CATsinstalled on the MFR handrail. Nicollier recon-nects the safety strap on the MFR and connectsthe CTVC cable to the RMS end effector. Foalethen installs the MFR handrail and the CTVCon the RMS. Nicollier deploys the TAs andinstalls the BSP center PIP pins.

The astronauts’ first servicing task for the dayis to change out the DF-224 computer with the

new Advanced Computer. Foale (in the MFR)maneuvers to the COPE Converter TransportModule and retrieves the Connector ConverterCaddy. Foale then maneuvers to the Bay 1worksite and installs handrail covers on thehandrails adjacent to the Bay 1 door if hedeems them necessary.

Meanwhile, Nicollier (free floating) translatesto the LOPE and opens the LOPE lid by dis-engaging four J-hook bolts. He removes theY-harness and mates one end of it to theAdvanced Computer. Nicollier also preparesthe Advanced Computer for Foale to removefrom the LOPE , releasing five of its six J-hooksand temporarily closing the LOPE lid andengaging a single J-hook.

Foale opens the Bay 1 door by disengaging sixJ-hooks and sets the integral door stay.Nicollier translates back to Bay 1 to assist Foalewith the computer swap. Foale removes theDF-224 computer by demating its nine electri-cal connectors and disengaging six J-hooks. Hetransfers it to Nicollier positioned at the MFRstanchion. Foale then installs the seven connec-tor converters on the HST harnesses.

Nicollier transfers the DF-224 computer toFoale for the maneuver to the LOPE worksite.Foale transfers the DF-224 computer back toNicollier and opens the LOPE lid by disengag-ing one J-hook. Foale removes the AdvancedComputer from the LOPE by disengaging oneJ-hook, then maneuvers back to Bay 1.

Meanwhile, Nicollier installs the DF-224 com-puter in the LOPE, engaging six J-hooks, thencloses the LOPE lid and engages four J-bolts.Nicollier translates back to the Bay 1 worksiteto assist Foale. Foale installs the AdvancedComputer in Bay 1 by engaging six J-hooks,mating two remaining Y-harness connectors,

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and mating seven harnesses. He then performsthe Advanced Computer video close-out,releases the door stay, and closes the Bay 1door, engaging six J-hooks.

After the computer change-out, Nicollier andFoale open the NPE, retrieving the Bay 1 NOBLand NOBL plug stringer from the NPE and

closing it. They install the Bay 1 NOBL on theBay 1 door by installing four NOBL vent holeplugs and connecting the NOBL ground cap tothe door J-bolt.

As the astronauts prepare to undertake theFGS-2 change-out, Nicollier replaces Foale onthe MFR and Foale becomes the free floater.

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Fig. 2-10 Fine Guidance Sensor change-out

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Nicollier and Foale retrieve a PFR/PFRExtender and set it up on the HST in FootRestraint 11. Nicollier retrieves the outboardFGS handhold from the ORUC forward fixtureand installs handrail covers at FGS-2 worksiteas needed. Foale deploys the aft fixture.

The astronauts open and secure the FGS baydoors and demate the FGS connectors andground strap. Nicollier installs four guidestuds on the FGS, then installs the FGS hand-hold and loosens the A latch. The FGS is nowready to be removed.

With Foale in the PFR and Nicollier holding theFGS handhold, the team removes the FGS asFoale gives clearance instructions. To ensuresuccessful installation of the replacement FGS,the team may practice reinsertion of the oldFGS back into the HST guiderails withoutlatching the latches or mating the connectorsfor mass handling evaluation.

After this practice insertion, Nicollier removesthe FGS and stows it on the aft fixture. Foalethen conducts a bay inspection. Next, Foaletranslates to the ORUC FSIPE, opens the lid,latches the lid in the open position, anddemates and secures the ground strap. In par-allel, Nicollier retrieves the other FGS hand-hold from the ORUC forward fixture andpositions himself for its installation on thereplacement FGS in the FSIPE.

After installing the handhold on the replace-ment FGS, Nicollier loosens the A latch. Then,with instructions and assistance from Foale,Nicollier removes the replacement FGS fromthe FSIPE and translates with it to the HST.Foale closes the FSIPE lid and engages one lidlatch. He then ingresses the PFR mounted onthe HST and prepares to remove the FGS mir-ror cover. Nicollier presents the FGS to Foale so

that the FGS mirror cover can be removed.Foale tethers to the cover, releases the slide locklever, and operates the handle to remove themirror cover. When the mirror cover isremoved, IVA repositions Nicollier on the MFRso the FGS can be installed.

Nicollier inserts the FGS with assistance fromFoale (see Fig. 2-10). Nicollier tightens the Alatch, removes the FGS handhold, and stows ittemporarily on the MFR, then installs the groundstrap and electrical connectors. After the electri-cal connectors are mated, IVA informs MissionControl to perform an aliveness test. Nicolliertakes the close-out photographs (video), closesand latches the doors, and checks the door seals.He then retrieves the HST PFR and stows it forlater reinstallation in the cargo bay. Foale stowsthe mirror cover on the ORUC.

Nicollier retrieves the FGS from the aft fixture.Foale stows the aft fixture, translates to theFSIPE, and opens the lid. Nicollier translates tothe FSIPE with the FGS. Foale assists Nicollierduring the FGS insertion into FSIPE. After fullinsertion, Nicollier tightens the A latch whileFoale mates the ground strap. Foale releasesthe FSIPE on-orbit latches and closes andsecures the lid. Nicollier stows the replace-ment FGS handhold in the forward fixture.Foale retrieves the PFR that was used for theFGS change-out and reinstalls it on the Shuttlebay adaptive payload carrier.

For the EVA Day 2 daily close-out, Foaleremoves the center pins on the BSP, inspects theFSS main umbilical mechanism, and retracts theTAs while Nicollier prepares the CATs installedon the MFR handrail for return to the airlock.Foale releases the MFR safety tether from theRMS in the event of contingency Earth return.Both astronauts return to the airlock with theMFR handrail and its installed CATs.

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EVA Day 3: Mate additional OCE-EK connec-tors for the new FGS-2. Change out SSAT.Replace E/STR #3 with SSR #3. Repair MLI.

On EVA Day 3, EVA astronauts Smith andGrunsfeld are scheduled to mate additionalOCE-EK connectors to allow for the on-orbitalignment optimization of the replacementFGS adjustable, articulated, fold flat #3 mirror.They will replace an S-band single access trans-mitter (SSAT) that failed in 1998. An identicalbackup transmitter has functioned perfectlyand HST’s observing program has not beenaffected. The astronauts also will install an SSRin place of an E/STR. Finally, they will under-take MLI repairs over the doors on Bays 5through 10.

The daily setup for EVA Day 3 is identical toEVA Day 2. Smith still exits the airlock with therequired CATs and CTVC installed on the MFRhandrail and transfers them to Grunsfeld. Hereconnects the safety strap on the MFR/RMSand connects the CTVC to the RMS end-effec-tor. Grunsfeld installs the MFR handrail andthe CTVC on the RMS. Smith deploys the TAand installs the BSP center PIP pins.

The first task of the day is the mating of theOCE-EK connectors. Grunsfeld on the RMStranslates to the Optical Telescope Assembly(OTA) Bay C door and opens the door via thethree J-hooks. He then demates the P11 connec-tor from the OCE, and mates the OCE-EK J/P11A with the OCE J11 and HST P11 connectors.The close-out photographs are taken and theBay C door is secured with its three J-hooks.

Grunsfeld on the MFR then opens the Bay 5 doorby disengaging six J-hooks, then secures thedoor in the open position. He prepares the oldSSAT-2 for removal by demating two circularconnectors and three coaxial connectors. He

installs a fastener retention block, removes eightnon-captive bolts/washers, and removes the oldSSAT-2. Grunsfeld transfers the SSAT-2 to Smith,who is free floating.

Smith brings the old SSAT-2 to the COPE, opensit, and retrieves the replacement SSAT. Hestows the old SSAT in the COPE, closes it, andtranslates back to Bay 5. Grunsfeld receives thereplacement SSAT-2 from Smith, installs it onthe Bay 5 door by engaging seven bolts, remov-ing the two connector caps, mating two circularconnectors, and mating three coaxial connec-tors (see Fig. 2-11). Grunsfeld then performs thevideo close-out. Because the SSR installation isthe next task, the Bay 5 door is left open.

The next change-out task is replacement of theE/STR-3 with a newer technology SSR-3.Grunsfeld demates the T-harness installed dur-ing SM2 and two other E/STR-3 connectors,being careful not to allow the powered-on P1connector to touch structure ground. Hesecures the P1 connector behind the cable har-ness along the side wall, demates the four key-hole fasteners, and removes the E/STR.

Smith and Grunsfeld translate to the COPE withthe E/STR-3. Smith releases the COPE lid latch-es and opens the lid. Smith and Grunsfeldremove SSR-3 from the COPE transport moduleand install the E/STR-3 into the COPE transportmodule. Grunsfeld translates back to the Bay 5worksite. Smith stows the T-harness in the COPElid, retrieves the J-harness, then closes and latch-es the lid. He then translates with the J-harness toBay 5 to assist with the SSR installation.

In parallel to Smith’s closure of the COPE,Grunsfeld installs the SSR into the #3 position(see Fig. 2-12). SSR-3 is mounted via four key-hole bolts. The SSR-3 connector caps areremoved and the connectors mated, then the

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J-harness is mated to the J-4 connectors onSSR-3 and SSR-1. The J-harness providesincreased capability for the SSR and HST.Grunsfeld takes the close-out video. With theassistance of Smith, Grunsfeld closes the doorand secures it with the six J-hooks.

The crewmembers now swap roles: Smith movesto the MFR and Grunsfeld becomes free floating.

Grunsfeld retrieves the MLI recovery bagsfrom ORUC ATM. Smith opens the NPE andretrieves the NOBLs for Bays 5 and 6 and a sin-gle NOBL plug stringer. He temporarily closesthe NPE by securing one latch.

Grunsfeld assists Smith throughout the NOBLinstallation process. Smith installs the Bay 6NOBL to the door stop and secures the handle

Fig. 2-11 S-Band Single Access Transmitter change-out

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attachment to the door handle. He removes thetwo Bay 7 tie wraps and stows them in thetrash bag, then removes the two Bay 8 patchesand stows them in an MLI recovery bag. Thepatches were installed during SM2.

Smith removes the original Bay 5 door MLIand stows it in an MLI recovery bag. He

installs the Bay 5 NOBL and secures it with thefour NOBL plugs, then connects the NOBLground cap to a J-bolt (see Fig. 2-13).

Smith retrieves the Bay 7 and Bay 8 NOBL andtwo vent plug stringers from the NPE andtemporarily closes the NPE, securing a singlelatch. He installs the Bay 7 NOBL, securing it

Fig. 2-12 Installation of Solid State recorder

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with the four NOBL plugs, then connects theNOBL ground cap to a J-bolt.

Smith installs the Bay 8 NOBL and secures itwith the NOBL plugs, then connects theNOBL ground cap to a J-bolt. He removes thetwo MLI patch kits installed on Bay 10 dur-ing SM2 and stows them in an MLI recoverybag, then removes the two original Bay 10

door MLI pieces and stows them in an MLIrecovery bag.

Smith retrieves the Bay 9 and Bay 10 NOBLand NOBL plugs from the NPE and closes theNPE, securing all three latches. He installs theBay 9 NOBL to the door stop and secures thehandle attachment to the door handle. Smiththen installs the Bay 10 NOBL and secures it

Fig. 2-13 New outer blanket layer installation

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with the four NOBL plugs, then connects theNOBL ground cap to a J-bolt.

For the Day 3 EVA close-out, Grunsfeldremoves the center pins on the BSP, inspectsthe FSS main umbilical mechanism, andretracts the TAs while Smith prepares the CATsinstalled on the MFR handrail for return intothe airlock. Smith releases the MFR safetytether from the RMS in the event of contin-gency Earth return. After completion of theEVA Day 3 close-outs, both astronauts return tothe airlock with the MFR handrail and itsinstalled CATs.

EVA Day 4: EVA Day 4 consists of a series ofscheduled and optional tasks: Install SSRFson the forward shell/light shield. Installhandrail covers on the Bays A and J handrails.Install Aft Shroud Latch Repair (ASRL) Kitson the +V2 aft shroud doors.

EVA crewmembers Foale and Nicollier arescheduled to install new insulation material onthe outer surfaces of the Telescope where MLIhas become degraded. Optional tasks are toinstall handrail covers where the paint cover-ing has debonded and install repair kits tofunctionally replace the degraded aft shrouddoor latches.

EVA Day 4 has a daily setup similar to that ofthe prior EVA days. Nicollier starts the day inthe MFR. Foale exits the airlock with therequired CATs installed on the MFR handrailand the CTVC and transfers them to Nicollier.Nicollier reconnects the safety strap on theMFR/RMS and connects the CTVC cable to theRMS end-effector. Nicollier then installs theMFR handrail and the CTVC to the RMS.Foale deploys the TAs and installs the BSPcenter PIP pins.

Foale opens the ORUC ASIPE by disengagingthe five lid latches. Nicollier opens the lid.Foale retrieves the five SSRF rib clamps andNicollier retrieves SSRFs 5, 6, and 7. Nicolliercloses the ASIPE lid temporarily by engaging asingle lid latch.

Foale and Nicollier install the five SSRF ribclamps on the HST station 358 rib. Working as ateam, Foale and Nicollier install SSRFs 5, 6, and 7.

Nicollier opens the ASIPE and retrieves SSRFs1, 2, 3, and 4. He then fully closes the ASIPE,engaging the five lid latches. Nicollier andFoale translate to HST and installs SSRFs 1 and 2.

When that task is complete, the IV crew rotatesthe FSS to the HST 30-degree position. Nicollierand Foale install SSRFs 3 and 4. Both theninstall two ASLR Kits on the two degraded +V2door latches if needed. The handrail coversalso can be installed, if needed, at this time.

For the final daily close-out, Foale stows theTAs, removes and stows the LGAPC, inspectsthe FSS main umbilical mechanism, andinspects the P105/P106 connector covers.Nicollier installs the CATs on the MFR handrailfor return to the cabin and demates and stowsthe MFR from the RMS. When the tasks arecomplete, both crewmembers enter the airlockwith the CATs-laden MFR handrail.

EVA Contingency Day. An unscheduled EVAday has been allocated for enhancing payloadmission success and for any payload require-ments on the HST redeployment day.

Redeploying the Telescope. The day followingEVA Day 4 will be devoted to any unscheduledEVA tasks and redeployment of the HST intoEarth orbit (see Fig. 2-14).

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The SAs are slewed to the Sun to generate elec-trical power for the Telescope and to charge thebatteries, and HGAs are commanded to theirdeployed position. When the battery chargingis complete, the RMS operator guides therobotic arm to engage HST’s grapple fixture.The ground crew commands Hubble to switchto internal power. This accomplished, crewmembers command Discovery’s electricalumbilical to demate from Hubble and open theberthing latches on the FSS. If any Telescopeappendages fail to deploy properly, two mis-

sion specialists can perform EVA tasks on theredeployment day, manually overriding anyfaulty mechanisms.

2.8 Future Servicing Plans

As the Hubble Space Telescope enters the 21stcentury, other enhancements are planned. Athird-generation instrument, the AdvancedCamera for Surveys (ACS), will greatly enhanceHST’s imaging capabilities. Shuttle astronautsplan to install the camera during SM3B.

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Fig. 2-14 Redeploying the Space Telescope

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ACS is truly an advanced camera, withpredicted performance improvementsone to two orders of magnitude over cur-rent Hubble science instruments. Itsunique characteristics and dramaticallyimproved efficiencies will exploit the full

potential of the Telescope to serve theneeds of the science community.

Periodic upgrades and servicing will ensurethat Hubble continues to yield remarkableadvances in our knowledge of the universe.

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