STS-103

Grunsfeld and Smith replacing gyroscopes on Hubble during the mission's first EVA
Names	Space Transportation System-103
Mission type	Hubble Space Telescope servicing
Operator	NASA
COSPAR ID	1999-069A
SATCAT no.	25996
Mission duration	7 days, 23 hours, 11 minutes 34 seconds
Distance travelled	5,230,000 kilometres (3,250,000 mi)
Spacecraft properties
Spacecraft	Space Shuttle Discovery
Launch mass	112,493 kilograms (248,005 lb)
Landing mass	95,768 kilograms (211,132 lb)
Crew
Crew size	7
Members	Curtis L. Brown Jr. Scott J. Kelly John M. Grunsfeld Jean-François Clervoy C. Michael Foale Steven L. Smith Claude Nicollier
EVAs	3
EVA duration	24 hours, 33 minutes
Start of mission
Launch date	20 December 1999 00:50:00 (1999-12-20UTC00:50Z) UTC
Launch site	Kennedy, LC-39B
End of mission
Landing date	28 December 1999 00:01:34 (1999-12-28UTC00:01:35Z) UTC
Landing site	Kennedy, SLF Runway 33
Orbital parameters
Reference system	Geocentric
Regime	Low Earth
Perigee altitude	563 kilometres (350 mi)
Apogee altitude	609 kilometres (378 mi)
Inclination	28.45 degrees
Period	96.4 minutes
Capture of Hubble
RMS capture	22 December 1999, 00:34 UTC[1]
RMS release	25 December 1999, 11:03 UTC[2]
Left to right; C. Michael Foale, Claude Nicollier, Scott J. Kelly, Curtis L. Brown Jr., Jean-Francois Clervoy, John M. Grunsfeld and Steven L. Smith Space Shuttle program ← STS-93 (95) STS-99 (97) → Hubble Space Telescope missions ← STS-82 (SM2) STS-109 (SM3B) →

STS-103, the 96th launch of the Space Shuttle and the 27th launch of Space Shuttle Discovery, was a Hubble Space Telescope servicing mission. It launched from Kennedy Space Center, Florida, on 19 December 1999 and returned on 27 December 1999 and was the last Shuttle mission of the 1990s. It was the only mission to span through Christmas after being delayed by 13 days for technical and weather reasons.

Position	Astronaut
Commander	Curtis L. Brown Jr. Sixth and last spaceflight
Pilot	Scott J. Kelly First spaceflight
Mission Specialist 1	John M. Grunsfeld Third spaceflight
Mission Specialist 2 Flight Engineer	Jean-François Clervoy, ESA Third and last spaceflight
Mission Specialist 3	/ Michael Foale Fifth spaceflight
Mission Specialist 4	Steven L. Smith Third spaceflight
Mission Specialist 5	Claude Nicollier, ESA Fourth and last spaceflight

• Smith and Grunsfeld – EVA 1
• EVA 1 start: 22 December 1999 – 18:54 UTC
• EVA 1 end: 23 December 1999 – 03:09 UTC
• Duration: 8 hours, 15 minutes
• Foale and Nicollier – EVA 2
• EVA 2 start: 23 December 1999 – 19:06 UTC
• EVA 2 end: 24 December 1999 – 03:16 UTC
• Duration: 8 hours, 10 minutes
• Smith and Grunsfeld – EVA 3
• EVA 3 start: 24 December 1999 – 19:17 UTC
• EVA 3 end: 25 December 1999 – 03:25 UTC
• Duration: 8 hours, 08 minutes

Seat[3]	Launch	Landing	Seats 1–4 are on the flight deck. Seats 5–7 are on the mid-deck.
1	Brown
2	Kelly
3	Grunsfeld	Foale
4	Clervoy
5	Foale	Grunsfeld
6	Smith
7	Nicollier

The primary objective of STS-103 was the Hubble Servicing Mission 3A. STS-103 had four scheduled Extravehicular Activity (EVA) days where four crew members worked 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 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 believed they understood the cause of the failures, although they could not be certain until the gyros were returned from space. Having fewer than three working gyroscopes would have precluded science observations, although the telescope would have remained safely in orbit until a servicing crew arrived.

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). It is the RSUs that the STS-103's astronauts changed. The RSUs each weigh 11.0 kilograms (24.3 lb) and are 12.8 by 10.5 by 8.9 inches (325 by 267 by 226 mm) in size.

In addition to replacing all six gyroscopes on the December flight, the crew replaced a Fine Guidance Sensor (FGS) and the spacecraft's computer. The new computer reduced the burden of flight software maintenance and significantly lowered costs. The new computer was 20 times faster and had six times the memory of the DF-224 computer previously used on Hubble. It weighs 32.0 kilograms (70.5 lb) and is 18.8 by 18 by 13 inches (478 by 457 by 330 mm) in size. The FGS installed was a refurbished unit that was returned from Servicing Mission 2. It weighs 217 kilograms (478 lb) and is 5.5 by 4 by 2 feet (1.68 by 1.22 by 0.61 m) in size.

A voltage/temperature improvement kit (VIK) was also 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 1.4 kilograms (3.1 lb).

The repair mission also installed 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 replaced one that failed in 1998. The SSAT weighs 3.9 kilograms (8.6 lb) and is 14 by 8 by 2+3⁄4 inches (356 by 203 by 70 mm).

A spare solid state recorder was also 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 was replaced by a second solid state recorder. The new recorder could hold approximately 10 times as much data as the old unit (12 gigabytes instead of 1.2 gigabytes). The recorder weighs 11.3 kilograms (25 lb) and is 12 by 9 by 7 inches in size.

Finally, the EVA crew replaced the telescope's outer insulation that had 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) 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 also carried hundreds of thousands of student signatures as part of the Student Signatures in Space (S3) program. The unique project provided 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.

It was the Discovery's last solo spaceflight. All later missions by Discovery were International Space Station missions.

Astronaut John Grunsfeld, who was one of the mission specialists on this mission, brought a "Planet Mars Flag" aboard Discovery.

NASA began a tradition of playing music to astronauts during the Gemini program, which was first used to wake up a flight crew during Apollo 15.^[5] Each track is specially chosen, often by their families, and usually has a special meaning to an individual member of the crew, or is applicable to their daily activities.^[5][6]

• List of human spaceflights
• List of Space Shuttle missions
• Outline of space science

• NASA mission summary Archived 15 August 2011 at the Wayback Machine
• STS-103 Video Highlights Archived 7 December 2013 at the Wayback Machine