<P> The Compton Gamma Ray Observatory ( CGRO ) was a space observatory detecting photons with energies from 20 k eV 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 450 km ( 280 mi ) to avoid the Van Allen radiation belt . It was the heaviest astrophysical payload ever flown at that time at 17,000 kilograms ( 37,000 lb ) . </P>
<P> The Compton Gamma Ray Observatory ( CGRO ) was a space observatory detecting photons with energies from 20 k eV 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 450 km ( 280 mi ) to avoid the Van Allen radiation belt . It was the heaviest astrophysical payload ever flown at that time at 17,000 kilograms ( 37,000 lb ) . </P>
when was the compton gamma ray observatory launched
when was the compton gamma ray observatory launched
1991
1991