Atlantis launched from Kennedy Space center on April 5, 1991 at 9:22 AM EST and landed at Edwards Air Force Base on April 11 at 6:55 AM EST. The shuttle orbited 93 times at an altitude of 248 nautical miles at an inclination of 28.45 degrees and travelled 2.5 million miles. The mission lasted 5 days, 23 hours, 32 minutes, and 44 seconds.
The first spacewalk since 1985 was performed by two astronauts to test the ability to move themselves and equipment about while working on the planned Space Station Freedom.
The primary payload, Gamma Ray Observatory (GRO), was deployed on flight day three. The GRO high-gain antenna failed to deploy on command; it was finally freed and manually deployed by Ross and Apt during an unscheduled contingency space walk, the first since April 1985. The GRO science instruments were Burst and Transient Source Experiment (BATSE), Imaging Compton Telescope (COMPTEL), Energetic Gamma Ray Experiment Telescope (EGRET) and Oriented Scintillation Spectrometer Experiment (OSSEE). Secondary payloads included Crew and Equipment Translation Aids (CETA), which involved scheduled six-hour space walk by astronauts Ross and Apt (see above); Ascent Particle Monitor (APM); Shuttle Amateur Radio Experiment II (SAREX II); Protein Crystal Growth (PCG); Bioserve/instrumentation Technology Associates Materials Dispersion Apparatus (BIMDA); Radiation Monitoring Equipment III (RME Ill); and Air Force Maui Optical Site (AMOS) experiment.
Atlantis was crewed by Commander Stephen R. Nagel, Pilot Kenneth D. Cameron, and Mission Specialists Jerry L. Ross, Jay Apt, and Linda M. Godwin.