Shuttle accident cut plans to retrieve now-falling satellite
CAPE CANAVERAL, Fla. -- Shuttle astronauts could have retrieved the NASA satellite now expected Friday to rain a half-ton of wreckage on Earth, 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 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 after the loss of Columbia and seven astronauts.
"UARS was originally conceived to be retrieved by the shuttle at the end of its mission. Due to changes in the shuttle program this was no longer an option," five NASA and contractor engineers from Goddard Space Flight Center in Greenbelt, Md., said in a UARS end-of-mission case study presented to the American Institute of Aeronautics and Astronautics in 2008.
In 2001, NASA engineers and astronauts reviewed concepts for a shuttle mission to retrieve the 35-foot-long satellite, which is 15 feet in diameter. At least one spacewalk would have been required to safely stow the satellite's power-producing solar wing and other appendages.
The job was considered doable.
But the satellite, which was launched on Discovery in 1991, operated for 14 years — more than a decade longer than expected. It wasn't decommissioned until 2005 — a time when NASA still was struggling to return the shuttle fleet to service.
"Capturing and returning UARS on a space shuttle was not considered an option due to the issues identified after the loss of Columbia," NASA spokesman Michael Curie added in an e-mail Wednesday.
Instead, NASA put in place a plan to use the spacecraft's propulsion system to lower the satellite from its operational orbit 350 miles above Earth down toward the upper reaches of the atmosphere.
The idea was to deplete the propulsion system of remaining toxic hydrazine rocket fuel that might make surviving wreckage dangerous to people on Earth. It also hastens atmospheric reentry and lessens the chance of an accident that might worsen already critical problems with orbital debris.
Most of the spacecraft will burn up during a fiery plunge back through the atmosphere. But analysts expect 26 pieces weighing a total of about 1,200 pounds to survive and strike Earth.
NASA officials and Air Force space surveillance trackers will not know exactly where the debris will fall until the reentry takes place. The wreckage will be distributed over a 500-mile-long swath.
Odds of any person being killed by falling debris: 1 in 3,600.
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