Payload Commander Steven L. Smith (bottom), and Mission Specialist John M. Grunsfeld, perform servicing tasks on the temporarily-captured Hubble Space Telescope. Grunsfeld is on a foot restraint connected to Discovery’s RMS robot arm. Smith, making
his second servicing visit to HST, is using handrails on the telescope. Credit: NASA
Servicing Mission 3A
STS-103 Discovery • December 19-27, 1999
The Hubble Space Telescope is alive and well and back on duty after a successful
servicing mission in December 1999. (SM3A). To prove it, NASA released two stunning
images taken by Hubble just two weeks after Discovery’s Christmas-time service call.
Discovery’s seven-member crew included two Hubble Servicing Mission veterans.
Launch of STS-103 What was originally conceived as a mission of preventive maintenance turned more urgent on November 13, 1999, when the fourth of six gyros failed
and Hubble temporarily closed its eyes on the universe. Unable to conduct science
without three working gyros, Hubble entered a state of dormancy called safe mode.
Essentially, Hubble “went to sleep” while it waited for help.
NASA decided to split the Third Servicing Mission (SM3) into two parts, SM3A and
SM3B, after the third of Hubble’s six gyroscopes failed. In accordance with NASA’s flight
rules, a “call-up” mission was quickly approved and developed and executed in a
record seven months.
Release of Hubble back into orbit The Hubble team has left the telescope far more
fit and capable than ever before. The new, improved, and upgraded equipment
included six fresh gyroscopes, six battery voltage/temperature improvement kits, a
faster, more powerful, main computer, a next-generation solid state data recorder,
a new transmitter, an enhanced fine guidance sensor, and new insulation.