GRO

Gamma Ray Observatory, also called Compton gamma-ray observatory

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General

Designation	21225 / 91027B
Launch date	5 Apr 1991
Country of origin	United States
Operator	NASA
Mission	Scientific: Astronomy
Perigee/Apogee	437/462 km
Inclination	28.4°
Period	93.5 min
Launch vehicle	STS 37
Mass at launch	15620 kg

The objective of the Compton GRO was to make comprehensive observations of gamma ray sources throughout the Universe. The observatory carried four scientific instruments that made gamma ray energy measurements from 0.1 million electron volts to 30,000 million electron volts.

Orbit reboost maneuver in 1993 extended mission life by 5 years. It recorded over 2600 gamma explosions.

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End of life

Out of service	Jun 2000
Cause	The failure of 1 gyroscope requires the deorbitation of the satellite in order to make sure it will not fall in a populated area. It is too large to completely burn in the atmosphere.
Decay	4 June 2000 06 UT, reentered in the Pacific, approx 4000 km of Hawaii

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External resources

http://cossc.gsfc.nasa.gov/

http://pao.gsfc.nasa.gov/gsfc/spacesci/structure/cgro.htm
http://cossc.gsfc.nasa.gov/images/epo/gallery/index.html
sat-index articles

Technical data

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Specifications

Prime contractor	TRW
Dimension	7.7 x 5.5 x 4.6 m
Mass at launch	15622 kg
Dry mass	13800 kg
Solar array	21.5 m
Stabilization	3-axis
DC power	EOL: 3980 W
Design lifetime	2 years (min)

Realtime acquisition via TDRS (tape recorders have failed).
Telemetry: 2287.5 MHz (realtime: 1/32 kbps, playback: upto 512 kbps)
Command: 2106.4 MHz (1/0.125 kbps)

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BATSE (Burst and Transcient Source Experiment)

Payload mass	976 kg
Industrial responsibility	Marshall SFC
Gamma-ray energy range	20-600 keV

Equipped with 8 detectors

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OSSE (Oriented Scintillation Spectrometer Experiment)

Payload mass	1820 kg
Industrial responsibility	Ball Aerospace
Gamma-ray energy range	100 keV-10 MeV

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COMTEL (imaging COMpton TELescope)

Payload mass	1460 kg
Industrial responsibility	MBB
Gamma-ray energy range	1-30 MeV
Angular resolution	1.7-4.4°

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EGRET (Energetic Gamma Ray Experiment Telescope)

Payload mass	1830 kg
Industrial responsibility	Goddard SFC
Gamma-ray energy range	20 MeV-30 GeV

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