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Like the name suggest, the Compton Gamma Ray Observatory detects gamma rays.
196 million dollars.
There are four: Hubble Space Telescope, Compton Gamma Ray Observatory, Chandra X-ray Observatory, and the Spitzer Space Telescope.
Space Shuttle Atlantis
It showed that most gamma ray bursts come from other galaxies, not our own. This means that gamma ray bursts must be extremely powerful.