Illustration of CGRO

The Compton Gamma Ray Observatory(CGRO) was the second of the NASA "Great Observatories" to be launched to space, following the Hubble Space Telescope.

Compton was:

• launched on the Space Shuttle Atlantis, mission STS-37, on 5 April 1991;
• de-orbited and entered the Earth's atmosphere on 4 June 2000.

CGRO carried a complement of four instruments that covered an unprecedented six decades of the electromagnetic spectrum, from 30 keV to 30 GeV. In order of increasing spectral energy coverage:

• Burst and Transient Source Experiment (BATSE) by NASA MSFC scoured the sky to short duration gamma ray bursts (20 to 600 kev) and conducted full sky surveys for long lived sources It consists of 8 detectors.
• OSSE (Oriented Scintillation Spectrometer Experiment) by Naval Research Laboratory detected gamma rays entering the field of view of any of four detectors in the 100 kev to 10 MeV range.
• Imaging Compton Telescope (COMPTEL) by Max Planck Institute was tuned to the 1-30 MeV energy range and determineed the angle of arrival within a degree and the energy of photons to within five percent at higher energies.
• Energetic Gamma Ray Experiment Telescope (EGRET) measured high energy (20 MeV to 30 GeV) gamma ray source positions to a fraction of a degree and photon energy to within 15 percent. EGRET was developed by NASA GSFC, Max Planck Institute, and Stanford University.

One great accomplishment of the CGRO was the discovery of terrestrial gamma ray sources in 1994 that come from thunderclouds .

The observatory was named after Dr. Arthur Compton, Nobel prize winner for work involved with gamma ray physics.

See Also

• Great Observatories program

External links

• NASA Compton Gamma Ray Observatory site
• New Scientist