Compton Gamma Ray Observatory Crashes on Earth

By Keith Cowing
June 4, 2000
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CGRO impact footprintNASA’s plan to bring the Compton Gamma Ray Observatory (CGRO) crashing back to Earth on Sunday worked according to

After engine burns at 12:00 AM EDT and 1:30 AM EDT, the CGRO was sent inexorably on a path towards destructive reentry
over the Pacific Ocean. CGRO crashed at around 2:20 AM EDT with debris strewn over a 2,500 mile long elipse of ocean
stretching from off the southeastern coast of Hawaii to the northwestern coast of South America.

NASA decided to deorbit the Compton Gamma Ray Observatory (CGRO) due to safety concerns that an additional gyroscope failure might lead to a potential uncontrolled reentry over populated areas.

Compton was launched by Space Shuttle mission STS-37 in 1991 for a 5 year mission. It has operated for more than 9
years and has met all of its primary science objectives. CGRO has made many scientific discoveries, some of them
“fundamental” according to NASA Associate Administrator for Space Science Ed Weiler.

CGRO was one of the heaviest spacecraft ever launched by NASA weighing around 33,000 pounds. When it reentered
the atmosphere, large pieces most certainly survived and hit the Earth. Some pieces may have been as large as 1 ton and hit at 200 miles per hour. The debris field or footprint was expected to be rather large. For this reason, the plan was to bring it back to Earth in a remote region of the Pacific Ocean.

Had the spacecraft reentered the atmosphere on its own, there was a probability of 1/1,000 that a human life could be lost according to Weiler. NASA estimates of
when the spacecraft would have come back to Earth (if not done so in a controlled fashion) ranged between 3 and 11 years. The 3 year estimate would have been the case if solar maximum activity
was at its highest possible level while the 11 year end of the range would have been the case if solar activity was low.

CGRO was a NASA cooperative program with participation from Germany, the Netherlands, the European Space Agency, and the United Kingdom. According to the STS-37
press kit: “the instruments onboard GRO, with sensitivities 10 times greater than that of earlier instruments, will scan active galaxies for new information on
celestial objects. GRO also can detect the very high temperature emissions from the vicinity of stellar black holes, thereby providing evidence for the existence of these
exotic objects. GRO observations of diffuse radiation will not only help resolve questions relating to the large scale distribution of matter in the universe, but also about
the processes that may have taken place shortly after the universe began in the theoretical energetic explosion or “Big Bang”.

° Watch Continuing TV Coverage, NASA TV

° Compton Gamma Ray Observatory Re-Entry Status Report 1 June 2000, NASA PAO

° Compton Gamma Ray Observatory Re-Entry Status Report 31 May 2000, NASA GSFC PAO

° Compton Gamma Ray Observatory Re-entry Activities, NASA PAO

° NASA Will Crash CGRO into the Pacific Ocean in June, SpaceRef

° NASA Preparing Plans for Destructive Reentry to End Compton Gamma Ray
Observatory’s Mission
, SpaceRef

SpaceRef co-founder, Explorers Club Fellow, ex-NASA, Away Teams, Journalist, Space & Astrobiology, Lapsed climber.