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TOPIC: compton gamma ray observatory

dafni

Date: Mar 8, 2008

compton gamma ray observatory

Compton Gamma Ray Observatory (Compton GRO), United States astronomical satellite that detected and studied gamma rays, a type of electromagnetic radiation with wavelengths shorter than those of visible light and X rays. Earths atmosphere blocks most gamma rays from telescopes on the ground, so scientists use satellites such as GRO for gamma-ray astronomy. Gamma rays originate in some of the universe's most violent events. Astronomers who study these events find gamma rays useful because gamma rays can pass through the dust between stars (see Interstellar Matter). This dust blocks other forms of radiation created by energetic events. So, by using a gamma-ray telescope, astronomers can study energetic processes that would otherwise be hidden, such as activity in the heart of the Milky Way Galaxy. GRO's four scientific instruments detected the entire range of gamma-ray emissions with greater precision than previously possible. The National Aeronautics and Space Administration (NASA) launched Compton GRO in 1991; the satellites mission ended in 2000.

Compton GRO Spacecraft

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Compton GRO weighed almost 16 metric tonsas much as a fully loaded semi-truck trailerwhen the space shuttle Atlantis deployed it on April 7, 1991. The spacecraft was the heaviest object that a shuttle had ever launched. GROs scientific instruments made up more than 5 metric tons of the satellites total mass. The rectangular satellite measured 4.5 m (15 ft) high and 9 m (30 ft) longas large as a school bus. Two solar panels (see Solar Energy), which generated power for GROs scientific instruments and communication systems, extended from the satellites sides like wings. The solar panels made the satellites width 21 m (69 ft).

Spacecraft Systems

GRO returned data to scientists on Earth through its high-gain antenna, which extended from the top front of the spacecraft. The antenna sent a signal from the observatory to one of the communications satellites that are part of NASAs Tracking and Data Relay Satellite System (TDRSS). The TDRSS satellite then relayed the data to a station on the ground. When GROs mission began, its scientific instruments fed data to two tape recorders aboard the observatory. When the tape recorders had collected about three hours worth of data, the recorders played back the data at high speed, sending the signals to a TDRSS satellite. GROs tape recorders began to fail in 1992, so the observatorys scientific instruments were forced to send data directly to the TDRSS system. To decrease the time that the observatory was out of touch with Earth during each orbit, NASA launched two additional TDRSS satellites, in 1993 and 1995.

The GRO had its own propulsion system. This set of small thruster rockets allowed the observatory to boost itself into a higher orbit if required. The satellite carried four fuel tanks for the thrusters. Three gyroscopes aboard GRO enabled engineers on Earth to guide and navigate the satellite.

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