Pictured is astronaut Jay Apt perched in the shuttle payload bay below the massive observatory. Compton is the largest civilian instrument ever flown - the whole observatory is roughly the size of a school bus. Apt and colleague Jerry Ross rescued the spacecraft from an unexpected problem by successfully freeing the stuck high gain antenna in an unplanned space walk. The second of NASA's planned Great Observatories for Space Astrophysics , the first being the Hubble Space Telescope , the Compton Gamma Ray Observatory has exceeded expectations of scientific discovery . Compton continues to search the depths of the universe for such high energy phenomena as gamma-ray bursts , blazars , and pulsars .
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