A NASA research satellite is expected to hit Earth in the coming days. Most of the six-ton, 35-foot long satellite will burn up on re-entry into the atmosphere, but 26 large chunks are expected to hit Earth's surface. Exactly where they will crash is hard to predict, but NASA does say the satellite is not expected to be over North America when it re-enters. It is the largest satellite to fall back to Earth uncontrolled since Skylab in 1979.NASA has revised its predictions and now says its defunct Upper Atmosphere Research Satellite will enter the atmosphere some time late September 23 or the morning of September 24. The 7-ton UARS satellite, the size of a school bus, is expected to break up into 26 pieces that will survive re-entry. NASA says the pieces have a 1 in 3200 probability of hitting a terrestrial inhabitant, but believes that the pieces will miss North America. A more accurate prediction will be issued within 12 hours of the projected breakup.
The UARS satellite was launched in 1991 by the Space Shuttle Discovery. At launch, it was 35-feet long, 15 feet in diameter, and weighed in at 13,000 pounds. It was used to measure ozone and chemical compounds found in the ozone layer which affect ozone chemistry and processes, as well as winds and temperatures in the stratosphere and the energy input from the Sun. "Together, these help define the role of the upper atmosphere in climate and climate variability," NASA said. It was officially decommissioned on December 14, 2005
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