The primary mission was the launch and deployment of the 7th Tracking and Data Relay Satellite (
TDRS-G) by means of the two-stage
Inertial Upper Stage (IUS)
solid rocket. It was built by TRW and weighs about . The satellite was ejected from ''Discovery's'' cargo bay exactly on time at 2:55 p.m. CDT, approximately six hours into the flight. The release of the satellite was overseen by Mission Specialists
Donald Thomas and
Mary Ellen Weber. About 15 minutes later, ''Discovery's'' Commander
Tom Henricks fired the shuttle's engines to raise the orbit and move away from the vicinity of the satellite and the IUS. At about 3:55 p.m., the IUS fired the first of two burns that would put TDRS-G into its proper, 22,000-mile-high geostationary orbit above the central Pacific Ocean at 178 degrees West longitude. The deployment operations utilized three separate control centers; the
White Sands ground station controlled the TDRS, the JSC Mission Control Center (MCC) controlled the shuttle, and the Inertial Upper Stage (IUS) control center at Onizuka Air Force Base in Sunnyvale California controlled the booster stage. Once it reached its destination, the fully deployed satellite had a wingspan of 57 ft. The TDRS was the sixth placed in operational use.
TDRS-1 was launched aboard
STS-6 on 1983-04-04 with a scheduled lifetime of seven years. The second satellite,
TDRS-B, was
lost aboard
Challenger on mission
STS-51-L.
TDRS-3 was deployed from
STS-26,
TDRS-4 from
STS-29,
TDRS-5 from
STS-43 and
TDRS-6 was deployed by
STS-54. The on-orbit
TDRS network was rearranged and included two fully operational spacecraft occupying the TDRS East and West slots, one on-orbit fully functional spare, TDRS-1, which was nearly depleted having exceeded its planned lifetime, and the partially operational TDRS-3 spacecraft dedicated to supporting the
Compton Gamma Ray Observatory and providing coverage an area that can't be seen by the other satellites known as the Zone of Exclusion. ==Additional payloads and experiments==