Just how important is the problem of orbital debris? At present (2012), there are roughly one thousand operational satellites, half of which are in near-Earth space, according to the Union of Concerned Scientists Satellite Database. But in addition to about 40 derelict satellites, the U.S. Space Surveillance Network is tracking more than 22,000 pieces of debris, each of which is larger than about 4 inches (10 cm), the reliable detection limit of their radars and telescopes. Only two weeks ago the explosion of a Russian upper stage rocket added over 500 large pieces of debris to the problem.
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