The Compton Observatory satellite (CO) formerly called Gamma Ray Observatory (GRO), at the end of the RMS manipulator arm of Shuttle Atlantis. CO was launched from Atlantis on Mission STS-37 of 5- 11 April 1991. The second of NASA's Great Observatories, CO will investigate the high-energy processes within supernovae, galaxies and pulsars. The instruments carried are; the Oriented Scintillation Spectrometer Experiment (OSSE) at top, the Imaging Compton Telescope (Comptel) centre dome, the Energetic Gamma Ray Experiment Telescope (EGRET) bottom dome, and the Burst and Transient Source Experiment (BATSE) with detectors at each corner of the satellite.