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STS-103: Home | The Crew | Cargo | Timeline | EVA

Servicing Mission 3A Configuration

IMAGE: Hubble servicing cargo
Discovery's payload bay with Hubble servicing cargo.

Centered in Discovery's cargo bay is the Orbital Replacement Unit Carrier. The carrier is a modified Spacelab pallet that contains the tools and replacement parts (see below) necessary to service the Hubble Space Telescope. Also, inside the cargo bay is the Flight Support System that will hold the telescope during servicing. Once the Hubble is attached to the support system, the system can rotate the telescope for appropriate access during spacewalks.

Rate Sensor Units (Gyroscopes)
The Rate Sensor Units allow the Telescope to point at stars, planets and other celestial targets. There are three aboard Hubble, and each unit contains two gyroscopes. Hubble needs three of these six gyroscopes to meet its very precise pointing requirements, and the other three are spares. Astronauts will replace all three units, leaving Hubble with six fresh gyroscopes. (MPEG Video Format - 1.5 M)

Fine Guidance Sensor
This is the second in a "round-robin" series of changeouts and refurbishments of the three fine guidance sensors, which allow fine pointing and keep Hubble stable. The SM3A refurbished Fine Guidance Sensor is the same unit that was returned from Servicing Mission 2. The Fine Guidance Sensor returned from this mission will be refurbished and upgraded for re-use on Hubble's fourth Servicing Mission. (MPEG Video Format - 1.5 M)

New Spacecraft Computer
The radiation-rugged computer will replace Hubble's original, outdated main computer. The new computer will dramatically increase operational capabilities, reduce the burden of flight software maintenance, and significantly lower operational costs. (MPEG Video Format - 1.0 M)

Voltage/Temperature Improvement Kits
As Hubble's batteries age, they become more susceptible to overheating if overcharged. The Voltage/Temperature Improvement Kit compensates for this by lowering the battery's charge termination voltage. Astronauts will install one kit for each of Hubble's six batteries.

Spare S-Band Single Access Transmitter
The transmitter replaces an aged and failed unit. That unit will be removed, returned to Earth and refurbished for a later flight. (MPEG Video Format - 1.0 M)

Spare Solid State Recorder
The digital data recorder will serve as a high capacity backup to the Solid State Recorder that replaced a mechanical tape recorder in 1997. It is essential for efficiently handling the high volumes of data from Hubble's newest instruments and for maintaining high science productivity.

New Outer Blanket Layer
Stainless steel sheets will be installed in various locations on the telescope to help control Hubble's internal temperature. Covered with a protective thermal coating, these sheets will fit over existing insulation that has degraded. The following three tasks below will be performed on SM3A, time permitting. If there is insufficient time, these tasks will be completed on SM3B. (MPEG Video Format - 1.5 M)

Shell/Shield Replacement Fabric
Flexible aluminized Teflon sheets will be added to the exterior surfaces of Hubble's forward shell and light shield. This protective covering provides additional insulation against the harsh space environment. (MPEG Video Format - 0.7 M)

Aft Shroud Latch Repair Kit
During Servicing Mission 2 on STS-61, astronauts observed galling on latches caused by high torque. The STS-103 astronauts will replace these latches on Hubble's bay door.

Handrail Covers
Fiberglass cloth, called beta cloth, will be fitted like sleeves around the handrails above the Fine Guidance Sensors bay to prevent contamination to the Aft Shroud area. Flaking paint was observed on these handrails during Servicing Mission 2.

What is a payload?
IMAGE: Shuttle payload bay
The formal designation as a "payload" indicates that the experiment will be accorded top priority in crew time and energies during the entire flight, along with all other experiments carrying the same "payload" designation.
Shuttle-Hubble History
IMAGE: Hubble in shuttle payload bay
The Hubble Space Telescope rests in Endeavour's payload bay during the first servicing mission STS-61 on December 4, 1993.
Related Links
*STS-103 Press Kit
*Media Reference Guide (PDF file, 3.3 Mb)
*STS-103 EVA Timeline
*STS-103 EVA Scenario

Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 04/07/2002
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