STS103

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This is a mission of the United States Space Shuttle.

Space Shuttle program
Mission Insignia

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Mission Statistics
Mission:STS-103
Shuttle:Discovery
Launch Pad: 39-A
Launch:December 19, 1999 7:50:00.069 p.m. EST
Landing: December 27, 1999 KSC 7:01:34 pm EST. Runway 33.
Duration: 7 days, 23 hours, 11 minutes 34 seconds
Orbit Altitude:317nm
Orbit Inclination:28.45 degrees
Distance Traveled:3.25 million miles
Crew photo
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Previous Mission:
STS-93
Next Mission:
STS-99

Crew

Mission Parameters

Space walks

  • Smith and Grunsfeld - EVA 1
  • EVA 1 Start: December 22, 1999 - 18:54 UTC
  • EVA 1 End: December 23, - 03:09 UTC
  • Duration: 8 hours, 55 minutes
  • Foale and Nicollier - EVA 2
  • EVA 2 Start: December 23, 1999 - 19:06 UTC
  • EVA 2 End: December 24, - 03:16 UTC
  • Duration: 8 hours, 10 minutes
  • Smith and Grunsfeld - EVA 3
  • EVA 3 Start: December 24, 1999 - 19:17 UTC
  • EVA 3 End: December 25, - 03:25 UTC
  • Duration: 8 hours, 08 minutes

Mission Highlights

The primary objective of STS-103 is the servicing of the Hubble Space Telescope. STS-103 has four scheduled Extravehicular Activity (EVA) days where four crew members will work in pairs on alternating days to renew and refurbish the telescope.

NASA officials decided to move up part of the servicing mission that had been scheduled for June 2000 after three of the telescope's six gyroscopes failed. Three gyroscopes must be working to meet the telescope's very precise pointing requirements, and the telescope's flight rules dictated that NASA consider a "call-up" mission before a fourth gyroscope failed. Four new gyros were installed during the first servicing mission (STS-61) in December of 1993 and all six gyros were working during the second servicing mission (STS-82) in February 1997. Since then, a gyro failed in 1997, another in 1998 and a third in 1999. The Hubble team believes they understand the cause of the failures, although they cannot be certain until the gyros are returned from space. Having fewer than three working gyroscopes would preclude science observations, although the telescope would remain safely in orbit until a servicing crew arrived.

In addition to replacing all six gyroscopes on the December flight, the crew will replace a guidance sensor, the spacecraft's computer and install a voltage/temperature kit for the spacecraft's batteries. A new transmitter, solid state recorder and thermal insulation blankets will also be installed.

Hubble's gyros spin at a constant rate of 19,200 rpm on gas bearings. This wheel is mounted in a sealed cylinder, which floats in a thick fluid. Electricity is carried to the motor by thin wires (approximately the size of a human hair). It is believed that oxygen in the pressurized air used during the assembly process caused the wires to corrode and break. The new gyros were assembled using nitrogen instead of oxygen. Each gyroscope is packaged in a Rate Sensor assembly. The Rate Sensors are packaged in pairs into an assembly called a Rate Sensor Unit (RSU's). It is the RSU's that the STS-103's astronauts will be changing. The RSU's each weigh 24.3 pounds and are 12.8 by 10.5 by 8.9 inches in size.

In addition to replacing all six gyroscopes on the December flight, the crew will replace a Fine Guidance Sensor (FGS) and the spacecraft's computer. The new computer will reduce the burden of flight software maintenance and significantly lower costs. The new computer is 20 times faster and has six times the memory of the current DF-224 computer used on Hubble. It weighs 70.5 pounds and is 18.8 by 18 by 13 inches in size. The FGS being installed is a refurbished unit that was returned from Servicing Mission 2. It weighs 478 pounds and is 5.5 by 4 by 2 feet in size.

A Voltage/temperature Improvement Kit (VIK) will be also be installed to protect spacecraft batteries from overcharging and overheating when the spacecraft goes into safe mode. The VIK modifies the charge cutoff voltage to a lower level to prevent battery overcharging and associated overheating. The VIK weighs about 3 pounds.

The repair mission will also install a new S-Band Single Access Transmitter (SSAT). Hubble has two identical SSATs onboard and can operate with only one. The SSATs send data from Hubble through NASA's Tracking Data Relay Satellite System (TDRSS) to the ground. The new transmitter will replace one that failed in 1998. The SSAT weighs 8.5 pounds and is 14 by 8 by 2 and 3/4 inches.

A spare solid state recorder will also be installed to allow efficient handling of high-volume data. Prior to the second servicing mission, Hubble used three 1970s style reel-to-reel tape recorders. During the second servicing mission one of these mechanical recorders was replaced with a digital solid state recorder. During this mission a second mechanical recorder will be replaced by a second Solid State Recorder. The new recorder can hold approximately 10 times as much data as the old unit (12 gigabytes instead of 1.2 gigabytes). The recorder weighs 25 pounds and is 12 by 9 by 7 inches in size.

Finally, the EVA crew will replace the telescopes outer insulation that has degraded. The insulation is necessary to control the internal temperature on the Hubble. The New Outer Blanket Layer (NOBL) and Shell/Shield Replacement Fabric (SSRF) will help protect Hubble from the harsh environment of space. It protects the telescope from the severe and rapid temperature changes it experiences during each 90 minute orbit as it moves from sunlight to darkness.

STS-103 will also carry hundreds of thousands of student signatures as part of the Student Signatures in Space (S3) program. The unique project provides elementary schools (selected on a rotating basis) with special posters to be autographed by students, then scanned onto disks and carried aboard a NASA Space Shuttle mission.

See also

External link

Previous Mission:
STS-93
Space Shuttle program Next Mission:
STS-99

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