Compton Gamma Ray Observatory

The Compton Gamma Ray Observatory (CGRO) was a NASA space observatory that detected X-rays and gamma rays from 20 keV to 30 GeV. It was launched from Space Shuttle Atlantis on STS-37 on 5 April 1991 and deorbited on 4 June 2000.

The second of NASA's Great Observatories after Hubble, it weighed 16,300 kg, the heaviest astrophysical payload flown at the time, and was named after physicist Arthur Compton.