Friday afternoon, a six-ton satellite is expected to fall out of orbit, mostly burning up in the atmosphere.  NASA calculates that twenty-six pieces will survive and crash somewhere on Earth.  Many people are understandably concerned, since there is a chance (a very, very small chance) that one of these pieces might hit someone on the ground.

Get a snapshot view of NASA's Upper Atmosphere Research Satellite (UARS), which will fall to Earth in 2011, in this infographic.
Source: All about our solar system, outer space and exploration

You’ve probably heard this on the news already, and there are plenty of apps and websites to keep you up to date on the satellite’s status.  But have you wondered what this old, defunct satellite was used for?

The Upper Atmosphere Research Satellite, or UARS, was launched in 1991 to study the ozone layer and determine what was causing it to disappear.  During its 14 years of operation, the UARS collected data proving chlorofluorocarbons (CFCs), used in air conditioning, aerosole sprays, and solvents, were reacting with ozone, destroying ozone molecules faster than natural cycles could replace them.

Since this discovery, 196 countries have signed the Montreal Protocol, agreeing to gradually stop production of CFCs.  The United States has already banned most CFC uses with the Clean Air Act and is starting to ban HCFCs (CFCs with added hydrogen).  According to the EPA, the ozone layer is already starting to recover.

There’s still a lot wrong with our climate, but the Montreal Protocol is a rare success story.  Kofi Annan, the former secretary-general of the United Nations, called it “the single most successful international agreement to date,” and experts estimate that the famous hole in the ozone layer over Antarctica will close sometime in the next 50 to 75 years.

So on Friday if you happen to see the satellite burning through the sky, remember that this isn’t just any old satellite.  This satellite helped make the world a better place.


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