The Compton Gamma-Ray Observatory is one of NASA's four "Great Observatories". It's specific mission is to study the sources and astrophysical processes (e.g., nuclear reactions, electron bremsstrahlung, matter-antimatter annihilation, elementary particle producation and decay, Compton scattering, and synchrotron radiation) that produce that highest energy electromagnetic radiation from the cosmos. GRO carries a complement of four instruments that provide simultaneous observations covering over five decades of energy from 0.1 MeV to 30 GeV: the Burst and Transient Source Experiment (BATSE), the Oriented Scintillation Spectrometer Experiment (OSSE), the Imaging Compton Telescope (COMPTEL), and the Energetic Gamma-Ray Experiment Telescope (EGRET).