Compton Gamma Ray Observatory

The Compton Gamma Ray Observatory ( CGRO ) was a space telescope for gamma-ray astronomy.

The first only as Gamma Ray Observatory ( GRO) designated satellite was launched with the STS -37 mission of the Space Shuttle Atlantis on April 5, 1991. With over 15 tons, it was the heaviest scientific satellite was launched into orbit so far from the Space Shuttle. After a few months he was renamed in honor of the physicist and Nobel Prize winner Arthur Holly Compton in Compton Gamma Ray Observatory.

CGRO was the second of four space-based telescopes, which were planned by NASA as part of the "Great Observatory program." The other satellites of this program are the Hubble Space Telescope, the Chandra X - Ray Observatory and the Spitzer Space Telescope.

Instruments

The instruments of CGRO detected with the 20 keV to 30 GeV from a wide range of the electromagnetic spectrum. Ordered by increasing energy, the instruments were:

• Burst and Transient Source Experiment ( BATSE ): Developed by the Marshall Space Flight Center of NASA instrument investigated in the energy range 20 to 600 keV by gamma-ray bursts. With eight detectors at each corner of the satellite could monitor all uncovered from the earth part of the sky.
• Oriented Scintillation Spectrometer Experiment ( OSSE ): Developed by the Naval Research Laboratory instrument consisted of four independently movable detectors for the range 0.05 to 10 MeV, optimized for observations of rapidly variable sources and the adjacent background.
• Imaging Compton Telescope ( COMPTEL ): This from the Max Planck Institute for Extraterrestrial Physics, SRON Utrecht, ESA and the University of New Hampshire developed instrument observed in the energy range 1-30 MeV a field of one steradian. Taking advantage of the Compton effect, the positions of the observed gamma-ray sources at 5 to 30 arc minutes could be accurately determined.
• Energetic Gamma Ray Experiment Telescope ( EGRET ): This developed by the Goddard Space Flight Center, Max Planck Institute for Extraterrestrial Physics and Stanford University spark chamber for the energy range 20 MeV to 30 GeV source positions were at about the degree, and the energies of gamma photons be determined to be about 15 percent accurate.

Results

Among the best known results of CGRO include:

• The first all-sky survey at 100 MeV energy. While 271 sources were detected with EGRET.
• A map of the sky in the emission of radioactive aluminum ( 26Al ) by COMPTEL.
• A total of about 2000 measurements of gamma-ray bursts with BATSE. Their uniform distribution in the sky indicated that they were not raised in the Milky Way but in distant galaxies.
• Distinction of GRBs into two classes - long and short.
• Discovery of blazars as a major source of high-energy gamma radiation.

Crash

The CGRO was well over the expected life of five years, as a failed one of the gyroscopes for attitude control on 6 December 1999. The loss of another gyroscope would have satellite uncontrollable and uncontrolled crash in the event of the risk of death case was calculated to be 1:1000. NASA chose the surviving telescope controls to bring over the Pacific Ocean to the crash, which reduced the risk to about 1:29 million. The mass of CGRO at this time was still about 14910 kg. A test firing of the engines was made on 28 May 2000. On 31 May and 1 June, the orbital height was reduced by more braking maneuvers. Took place on June 4, 2000 at 03:56 UTC a third brake ignition of 21 minutes' duration. A mission in orbit later, the fourth brake ignition was at 05:22 UTC performed again for 30 minutes. This was enough to let enter CGRO to 06:10 UTC in the Earth's atmosphere. The remaining mass during re-entry was estimated at 14010 kg, of which about 30 to 40 debris could have reached the water surface. These were for the first time that NASA satellite controlled to crash.