Compton Gamma Ray Observatory

CGRO

Mission Profile

Compton Gamma Ray Observatory (CGRO) was one of NASA's four Great Observatories, launched on 5 April 1991 from the Space Shuttle Atlantis into low Earth orbit to study gamma-ray sources across the entire sky. Its four instruments — BATSE, OSSE, COMPTEL, and EGRET — covered seven decades of gamma-ray energy, from 20 keV to 30 GeV, providing the most comprehensive gamma-ray census of the universe ever conducted at the time. CGRO discovered that gamma-ray bursts are isotropically distributed across the sky, proving they must be cosmological rather than galactic in origin, and detected the first gamma-ray blazars, pulsars, and solar flares. The 17-tonne observatory was deliberately deorbited in June 2000 after a gyroscope failure raised concerns about a potential uncontrolled reentry over populated areas.