Most Of The Seven-Ton Spacecraft Will Burn Up Before Reaching The Ground

NASA's Upper Atmosphere Research Satellite (UARS), which ceased operations on December 14, 2005, is expected to re-enter the Earth's atmosphere Friday morning, but NASA scientists are still not sure where the remains of the seven-ton satellite will eventually fall to the ground.

NASA Photo

ABC News reports that NASA scientist Mark Matney said increased solar activity is causing the satellite's orbit to decay faster than originally anticipated. When it does re-enter the atmosphere, it will be the largest object to do so since Skylab in 1979.

NASA's chief orbital debris scientist Nicholas Johnson said that 26 parts of the satellite are expected to survive re-entry, and "(a)ll these ... have been identified as potentially causing damage if they hit a structure or a person but the odds of that are very, very, low."

How low? One in about 21 trillion for any individual. But the risk that one of the Earth's 7 billion people will be hit is closer to one in 3,200. NASA says it won't be able to accurately forecast where the satellite will fall until about two hours before its re-entry, and the target area encompasses everything from 57 degrees north to 57 degrees south latitude ... or just about the entire populated area of the Earth.

NASA estimates the debris footprint will be about 500 miles long, and says that anyone finding something suspected to be a piece of UARS should not touch it. Contact a local law enforcement official for assistance.

According to NASA, the UARS was launched from the Space Shuttle Discovery on September 15, 1991, the seven-ton spacecraft orbited the Earth more than 78,000 times, using 10 onboard scientific instruments to collect data on a variety of chemicals, including carbon dioxide, ozone, chlorine, methane, nitrogen oxides and chlorofluorocarbons.

As a result, scientists have gained a better understanding of the energy input, chemistry and dynamics of the upper atmosphere and the coupling between the upper and lower atmosphere. As the first satellite dedicated to studying stratospheric science, UARS focused on the processes that lead to ozone depletion, complementing and amplifying the measurements of total ozone made by the Total Ozone Mapping Spectrometer (TOMS) onboard NASA's Nimbus-7 and the Russian Meteor-3 satellites. UARS also measured winds and temperatures in the stratosphere, as well as the energy input from the Sun, research that is now being applied to improve weather forecasting models and help scientists understand the forces behind global climate change.

FMI: http://science.nasa.gov/missions/uars/