24/09 NASA Says Satellite Falls to Earth, but Location a Mystery

By KEVIN DREW and KENNETH CHANG

Published: September 24, 2011

Debris from a six-ton satellite fell back to Earth but its location remained a mystery as scientists searched for debris, NASA said early on Saturday.

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NASA, via Associated Press

The Upper Atmosphere Research Satellite, which fell to Earth late Friday or early Saturday, as it deployed from the space shuttle in 1991.

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The Upper Atmosphere Research Satellite plunged back to Earth between 11:23 p.m. ET and 1:09 ET, NASA said on its Web site. The re-entry time and location were still not known, the agency said, adding that the satellite was passing eastward over Canada and Africa, as well as vast portions of the Pacific, Atlantic and Indian Oceans during that period.

The fate of the satellite stirred online interest and speculation Friday and early Saturday. NASA said through Twitter that debris remained the property of the U.S. government and warned that people should not approach or touch any pieces they might come across.

The satellite was expected to re-enter between 11:45 p.m. Friday and 12:45 a.m. Saturday. A day earlier, NASA had said it expected re-entry on Friday afternoon.

“The satellite’s orientation or configuration apparently has changed,” the space agency said in an earlier update. Perhaps some piece had broken off, leaving it more streamlined as it tumbled through the upper atmosphere. “That is now slowing its descent,” NASA said.

The satellite circles the Earth on a tilted orbit, and as the planet turns each day, different locations pass underneath.

At least 26 pieces, the largest at 330 pounds, are expected to survive the plunge and land along a path 500 miles long.

NASA has forecast a 1-in-3,200 risk that debris from the satellite could injure someone, and the risk for any individual is infinitesimal. NASA’s Twitter feed emphatically said: “The chances that you (yes, I mean YOU) will be hit by a piece of the #UARS satellite today are one in several trillion. Very unlikely.”

There are no known instances of anyone being injured by falling space debris (though in 1997, a woman in Oklahoma was brushed by a piece of mesh from a Delta 2 rocket booster that did her no harm). When the space shuttle Columbia disintegrated during re-entry in 2003, the seven astronauts aboard died, but no one on the ground was hurt as 42.5 tons of debris showered down from West Texas to southwest Louisiana.

NASA satellites also receive considerably more attention when they come back to Earth than other debris of similar size. About one satellite five metric tons or larger re-enters the atmosphere every year. For example, on a test flight of its Falcon 9 rocket in June 2010, the Space Exploration Technologies Corporation placed the second stage and a prototype capsule into orbit. That object, comparable in weight to the Upper Atmosphere Research Satellite, came crashing back to Earth two and a half weeks later, close to the northeast coast of South America with hardly a media ripple.

The UARS satellite was launched in 1991 by the space shuttle Discovery and was decommissioned in 2005, when it was placed into a lower orbit so it would not cause any problems for the International Space Station.

Kevin Drew reported from Hong Kong, and Kenneth Chang from New York.