Sunday, 25 September 2011
A 6-ton NASA satellite on a collision course with Earth clung to space Friday, apparently flipping position in its ever-lower orbit and stalling its death plunge. The old research spacecraft was targeted to crash through the atmosphere sometime Friday night or early Saturday, putting Canada, Africa and Australia in the potential crosshairs, although most of the satellite should burn up during re-entry. The United States wasn't entirely out of the woods; the possible strike zone skirted Washington state.
Until Friday, increased solar activity was causing the atmosphere to expand and the 35-foot, bus-size satellite to free fall more quickly. But late Friday morning, NASA said the sun was no longer the major factor in the rate of descent and that the satellite's position, shape or both had changed by the time it slipped down to a 100-mile orbit.
On Friday night, NASA said it expected the satellite to come crashing down between 11 p.m. and 3 a.m. EDT. It was going to be passing over the Atlantic, Pacific and Indian oceans at that time, as well as Canada, Africa and Australia. "The risk to public safety is very remote," NASA said in a statement.
The Aerospace Corp., which tracks space debris, also estimated the strike would happen sometime between about 11 p.m. and 3 a.m. EDT, which would make a huge difference in where the debris falls. Its projections also put almost all of the U.S. in the clear — with Washington state the lone holdout.
Any surviving wreckage is expected to be limited to a 500-mile swath. The Upper Atmosphere Research Satellite, or UARS, will be the biggest NASA spacecraft to crash back to Earth, uncontrolled, since the post-Apollo 75-ton Skylab space station and the more than 10-ton Pegasus 2 satellite, both in 1979. Russia's 135-ton Mir space station slammed through the atmosphere in 2001, but it was a controlled dive into the Pacific. Some 26 pieces of the UARS satellite — representing 1,200 pounds of heavy metal — are expected to rain down somewhere. The biggest surviving chunk should be no more than 300 pounds.
The $740 million UARS was launched in 1991 from space shuttle Discovery to study the atmosphere and the ozone layer. At the time, the rules weren't as firm for safe satellite disposal; now a spacecraft must be built to burn up upon re-entry or have a motor to propel it into a much higher, long-term orbit. NASA shut UARS down in 2005 after lowering its orbit to hurry its end. A potential satellite-retrieval mission was ruled out following the 2003 shuttle Columbia disaster, and NASA did not want the satellite hanging around orbit posing a debris hazard.
UARS Satellite Crash Seen In Italy [VIDEO] >> http://www.metacafe.com/watch/7289524/nasa_satellite_fragments_uars_crash_in_italy/
