Editing Great Observatories program (section)

=== Compton Gamma Ray Observatory ===
[[File:CGRO s37-96-010.jpg|thumb|Compton Gamma Ray Observatory]]

{{Main|Compton Gamma Ray Observatory}}

Gamma rays had been examined above the atmosphere by several early space missions. During its [[HEAO Program|High Energy Astronomy Observatory Program]] in 1977, NASA announced plans to build a "great observatory" for [[gamma-ray astronomy]]. The Gamma Ray Observatory (GRO), renamed [[Compton Gamma-Ray Observatory]] (CGRO), was designed to take advantage of the major advances in detector technology during the 1980s. Following 14 years of effort, the CGRO was launched on 5 April 1991.<ref>{{cite web|url=http://heasarc.gsfc.nasa.gov/docs/cgro/epo/brochures/compton/bro5.html|title=Gamma-Ray Astronomy in the Compton Era: The Instruments|access-date=2007-12-07|work=Gamma-Ray Astronomy in the Compton Era|publisher=NASA (GSFC)| archive-url = https://web.archive.org/web/20090224125500/http://heasarc.gsfc.nasa.gov/docs/cgro/epo/brochures/compton/bro5.html | archive-date=2009-02-24| url-status=dead}} {{PD-notice}}</ref> One of the three [[gyroscope]]s on the Compton Gamma Ray Observatory failed in December 1999. Although the observatory was fully functional with two gyroscopes, NASA judged that failure of a second gyroscope would result in inability to control the satellite during its eventual return to Earth due to orbital decay. NASA chose instead to preemptively de-orbit Compton on 4 June 2000.<ref>{{cite web |url=https://spaceflightnow.com/cgrodeorbit/index.html|title=NASA space telescope heads for fiery crash into Pacific|first=William|last=Harwood|publisher=Spaceflight Now|access-date=2020-02-02}}</ref> Parts that survived reentry splashed into the [[Pacific Ocean]].