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.