STS-103

STS-103

Astronauts Steven Smith and John Grunsfeld replacing rate sensor units
Mission type	HST servicing
Operator	NASA
COSPAR ID	1999-069A
SATCAT №	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-39A
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	563 kilometres (350 mi)
Apogee	609 kilometres (378 mi)
Inclination	28.45 degrees
Period	96.4 minutes
Capture of Hubble
RMS capture	22 December 1999, 00:34 UTC
RMS release	25 December 1999, 11:03 UTC
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 STS-99 →

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

STS-103 was a Hubble Space Telescope servicing mission by Space Shuttle Discovery. The mission launched from Kennedy Space Center, Florida, on 19 December 1999 and returned on 27 December 1999.

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.