Wednesday, September 21, 2011

6 Ton NASA Satellite Falling From the Sky

Upper Atmosphere Research Satellite (UARS), credit NASA MSFC
Sometime near Friday, September 23, 2011, the Upper Atmosphere Research Satellite (UARS) will crash back to Earth.  UARS helped to define the role of the upper atmosphere in climate and climate variability, by measuring ozone and chemical compounds found in the ozone layer which affect ozone chemistry and processes.  UARS also helped characterize winds and temperatures in the stratosphere as well as the energy input from the Sun.  All of these helped better understand our upper atmosphere and Earth's climate.

It turns out that the this huge satellite may have some pieces which reach ground level.  Sounds exciting!  Don't touch though. ran an article about how FEMA is on alert for any issues.  You can read it: FEMA Prepared for Dead NASA Satellite's Plunge to Earth This Week.

From the article, 
Numerically speaking it comes out to a chance of 1 in 3,200 that one person anywhere in the world might be struck by a piece of debris. "So those are actually, obviously, very, very low odds that anything — anybody is going to be impacted by this debris," Johnson added.
Pretty small odds indeed... unless you are the person that gets hit... actually, I think that seems like very large odds.  Given that 2/3 of the planet is covered by water, that number seems ridiculously high... anyone else have any thoughts about it?

EDIT: Thought I would update the article with my comment below in case someone doesn't read the comment.  The 1 in 3200 is integrated over the entire world population.  The odds for any individual is 1 in 2.1E13 or 1 in 21 Trillion.  Very small odd indeed.


  1. Considering that the odds of dying from natural forces (heat, storm, quake, etc) are 1 in 3357, I don't really consider the odds of not getting hit by that satellite to be all that good. Just sayin'

  2. What I really don't understand about this is that the satellite hitting the Earth is a deterministic event - that is to say it will happen at a given time. A natural disaster is a pseudorandom event - we cannot predict when or where any of them will happen (given the appropriate amount of time away from the event (before a hurricane forms for instance)). How can those two events have such similar statistics?

  3. Nevermind, I figured out why the values are so large. They are integrated across the worlds population. The risk for an individual is 1 in 3200 * (world's population, about 6.7 billion right now). Therefore, uncorrelated odds of 1 in 2.1E13 or 1 in 21 trillion. That seems much more reasonable.


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