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Friday, September 23, 2011

Will a satellite land on your head?


You will probably miss your chance to get hit by a piece of NASA’s UARS (Upper Atmosphere Research Satellite), which is expected to re-enter Earth’s atmosphere early Saturday morning, UTC (universal time coordinated, or Greenwich mean time).  Although most of the satellite will burn up harmlessly, two dozen or so pieces are expected to make their way to the ground.  As of this writing, the UARS is predicted to hit somewhere in the South Pacific. 


If you’re reading this post before the satellite lands, you can get updates from NASA here.  You can also read about satellite re-entry.  


So, what are your chances of being hit by the debris?  Very slim even if you happen to be in a rowboat in the Pacific Ocean at exactly the right time.  The risk that any particular person will be hit is less than one in a trillion. 


 UARS orbit history


UARS orbit history
Credit: NASA


The UARS was launched in 1991 with the purpose of studying Earth’s atmosphere.  Among its missions was the study of the photochemistry of the ozone layer and of UV and visible light.  It was decommissioned in 2005.

You can see video of the satellite tumbling down to Earth and read more about the satellite on the Planetary Society and Bad Astronomy blogs.