The
Compton Gamma Ray Observatory (
CGRO) was a
space observatory detecting light from 20 keV to 30 GeV in Earth orbit from 1991 to 2000. It featured four main telescopes in one spacecraft, covering X-rays and
gamma rays, including various specialized sub-instruments and detectors. Following 14 years of effort, the observatory was launched from
Space Shuttle Atlantis during
STS-37 on April 5, 1991, and operated until its deorbit on June 4, 2000. It was deployed in
low earth orbit at to avoid the
Van Allen radiation belt. It was the heaviest astrophysical payload ever flown at that time at .