Doomed U.S. satellite headed back to Earth Friday

A defunct NASA research satellite about the size of a bus was due to come crashing back to Earth on Friday, showering debris over a still unknown part of the planet.Scientists were unable to pinpoint the time and place where the Upper Atmosphere Research Satellite, or UARS, will land due to unpredictable changes in the thickness of the atmosphere, fueled in part by a powerful solar flare on Thursday.

The solar flare released a blitz of highly charged particles called a coronal mass ejection in the direction of Earth. When the particles slam into the atmosphere, they cause it to heat up and expand, which in turn impacts the density of the air UARS is encountering as it tumbles uncontrollably in orbit.

Nevertheless, North America is out of the zone where up to 26 pieces of UARS debris, weighing a total of about 1,100 pounds (500 kg), is expected to fall Friday, NASA said on its website.

With most of the planet covered in water and vast uninhabited deserts and other land directly beneath the satellite’s flight path, the chance that someone would be hit by falling debris was 1-in-3,200, NASA said.

The satellite flies over most of the planet, traveling between 57 degrees north and 57 degrees south of the equator.

UARS was dispatched by a space shuttle crew in 1991 to study ozone and other chemicals in Earth’s atmosphere. It completed its mission in 2005 and has been slowly losing altitude, pulled by the planet’s gravity, ever since.

The satellite is one of about 20,000 pieces of space debris loitering in orbit around Earth. Something the size of the 13,000-pound (5,897 kg) UARS falls back into the atmosphere about once a year.

NASA held a news conference earlier this month about UARS’ re-entry and has been posting daily updates on its website, www.nasa.gov.

 

CAPE CANAVERAL, Florida (Reuters) – By Irene Klotz(Editing by Tom Brown and Bill Trott)