Advanced Communications Technology Satellite

STS-51

Discovery in orbit, seen from the SPAS astronomy platform
Mission type	Satellite deployment Astronomy
Operator	NASA
COSPAR ID	1993-058A
SATCAT №	22795
Mission duration	9 days, 20 hours, 11 minutes, 11 seconds
Distance travelled	6,608,628 kilometers (4,106,411 mi)
Orbits completed	157
Spacecraft properties
Spacecraft	Space Shuttle Discovery
Landing mass	92,371 kilograms (203,643 lb)
Payload mass	18,947 kilograms (41,771 lb)
Crew
Crew size	5
Members	Frank L. Culbertson, Jr. William F. Readdy James H. Newman Daniel W. Bursch Carl E. Walz
Start of mission
Launch date	12 September 1993, 11:45 (1993-09-12UTC11:45Z) UTC
Launch site	Kennedy LC-39B
End of mission
Landing date	22 September 1993, 07:56 (1993-09-22UTC07:57Z) UTC
Landing site	Kennedy SLF Runway 15
Orbital parameters
Reference system	Geocentric
Regime	Low Earth
Perigee	300 kilometres (190 mi)
Apogee	308 kilometres (191 mi)
Inclination	28.45 degrees
Period	90.6 min
Left to right: Culbertson, Bursch, Walz, Readdy, Newman Space Shuttle program ← STS-57 STS-58 →

Left to right: Culbertson, Bursch, Walz, Readdy, Newman

STS-51 was a Space Shuttle Discovery mission that launched the Advanced Communications Technology Satellite (ACTS) in September 1993. The flight also featured the deployment and retrieval of the SPAS-ORFEUS satellite and its IMAX camera, which captured spectacular footage of Discovery in space. A spacewalk was also performed during the mission to evaluate tools and techniques for the STS-61 Hubble Space Telescope servicing mission later that year. STS-51 was the first shuttle mission to fly a GPS receiver, a Trimble TANS Quadrex. It was mounted in an overhead window where limited field of view and signal attenuation from the glass severely impacted receiver performance. (Full triple-redundant 3-string GPS would not happen until 14 years later with STS-118.)

STS-51 was notable for having been scrubbed three times on the launchpad, each time after the crew had boarded the spacecraft:

The Advanced Communications Technology Satellite was deployed on flight day 1. This satellite served as a test bed for advanced experimental communications satellite concepts and technology. Its Transfer Orbit Stage (TOS) upper stage fired on time 45 minutes after deployment and boosted the satellite to geosynchronous altitude on the first day of the mission.