Shuttle astronauts could have retrieved the NASA satellite now expected to rain a half-ton of wreckage on Earth on Friday, but that option was discarded after the 2003 Columbia accident.
Just like NASA's flagship Hubble Space Telescope, the 6.5-ton Upper Atmosphere Research Satellite (UARS) was designed in the 1980s with a large, pin-like grapple fixture so the shuttle's robot arm could deploy and retrieve it.
The intent was to enable shuttle astronauts to bring the behemoth home at the end of its scientific life. But NASA abandoned that option when the space agency reduced its shuttle mission schedule to a bare-bones minimum after the loss of Columbia and seven astronauts.
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