For the last two decades, the Upper Atmosphere Research Satellite was orbiting Earth. Six years back, the satellite arrived at what NASA called the "end of a productive scientific life". By Saturday, UARS is expected to come crashing back to Earth. Resource for this article: UARS satellite pieces have 1 in 3,200 chance of hitting Earth

How UARS has lived

The Upper Atmosphere Research Satellite was first put into orbit in 1991. the Earth’s atmosphere, including the ozone layer, was studied with the satellite. At first, UARS was meant to last about three years. Shutting down UARS was the best choice after 14 years. Still, sixty percent of instruments were still working on the satellite. The size of UARS could be compared to a bus. It has mostly gold foil-like material on it too.

Coming down might hurt

NASA explained that the satellite is a “heavily decaying orbit.” Between September 22 and 24, the UARS is expected to get back to the Earth’s atmosphere. The atmosphere is expected to melt away much of the satellite. Still, there could possibly be as many as 100 separate portions that don’t get burned up. Some of the portions will be as heavy as 300 pounds. NASA believes that UARS probably will not hit ground. There is a 1 in 3,200 chance any piece will hit the ground. The only continent that is not within the fall zone is Antarctica. There's a 1 in 20 trillion chance that each piece will hit an individual.

National Aeronautics and Space Administration keeping things safe

There will be updates from NASA every two hours. The UARS satellite will be safe. Even with that, the best estimate is that NASA will be able to provide two hours' warning on the UARS re-entry. UARS is falling fast. This is due to the solar activity going on. The increased solar activity is also blamed for troubles with communications satellites. Though UARS is falling from the sky quickly, it is just one of the estimated 22,000 portions of "space junk" revolving about the earth.

Information from

MSNBC: http://www.msnbc.msn.com/id/44580262/ns/technology_and_science-space/#.T...

NPR: http://www.npr.org/blogs/thetwo-way/2011/09/19/140598814/space-junk-will...

NASA.gov: (PDF) http://www.nasa.gov/pdf/585584main_UARS_Status.pdf

Slatest: http://slatest.slate.com/posts/2011/09/19/uars_climate_satellite_expecte...

LA Times: http://latimesblogs.latimes.com/nationnow/2011/09/space-junk-expert-on-w...