by Staff Writers
Washington (AFP) Sept 21, 2011
The US space agency has narrowed down its prediction of when a defunct six-ton satellite will crash back to Earth, saying on Wednesday that it is expected to land on September 23, US time.
"The time reference does not mean that the satellite is expected to re-enter over the United States. It is simply a time reference," NASA said on its website.
"Although it is still too early to predict the time and location of re-entry, predictions of the time period are becoming more refined."
NASA had previously said the satellite could hit Earth as early as Thursday, September 22 or as late as Saturday, September 24.
All but 26 pieces of the Upper Atmosphere Research Satellite (UARS) are expected to burn up on re-entry into Earth's atmosphere, but where exactly they will land remains a mystery.
Orbital debris scientists say the pieces will fall somewhere between 57 north latitude and 57 south latitude, which covers most of the populated world. The debris footprint is expected to span 500 miles (800 kilometers).
UARS is the biggest NASA spacecraft to come back in three decades, after Skylab fell in western Australia in 1979.
The risk to human life and property from UARS is "extremely small," NASA said, adding that in 50 years of space exploration no one has ever been confirmed hurt by falling space junk.
More frequent updates are scheduled for 12, six and two hours before it lands.
But even at two hours out, debris trackers will not be able to predict landing with an accuracy greater than 25 minutes of impact, or within a potential span of 7,500 miles (12,000 kilometers), NASA said.
"Part of the reason it is so uncertain is the spacecraft itself is rather unwieldy looking and it tumbles and we can't predict exactly how it is going to be tumbling," said Mark Matney, an orbital debris expert at NASA.
"Even as it tumbles that could change exactly where it is going to land."
Space Technology News - Applications and Research
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NASA bus-sized satellite to crash-land this week
Washington (AFP) Sept 21, 2011
What goes up must come down. But where? That's the big question when it comes to a 20-year-old NASA satellite the size of a tour bus which is careening toward Earth and set to crash-land later this week. The US Department of Defense and NASA are tracking the six-ton spacecraft, which poses a one-in-3,200 risk of hitting one of the seven billion people on the planet, the US space agency s ... read more
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