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Another warning from the GAO: Is GPS still failing?

By: driver
Last year, the GAO wrote an extensive report on the state of GPS and how it may fail if caution is not taken in the acquisition process.  In September, another warning was issued:
A follow-up report released Sept. 15 credited the Air Force with making improvements but warned that a delay in launching one of the next-generation satellites could still drop the number of operational orbiting satellites to less than 24.
The Air Force is rebutting this, but instead of getting into the political side of the debate, I’ll stick with the technical side.  Last year on The Nog, I published an in-depth technical analysis of the worst case – what if up to nine GPS satellites failed?  What would that do to the navigation accuracy to which we are all addicted?  This is a good time to bring those results up again. See the original analysis here: http://blogs.agi.com/navigationAccuracy/?p=196. Here’s the baseline accuracy we have as of May 2009: Baseline Navigation Accuracy The bottom line is, do not sell your GPS receiver—the average accuracy will not change, though there could be brownouts for a few minutes each day if nine satellites were to fail without replacement. This is just not going to happen.  I think it’s good that the GAO is warning the AF, however. It keeps everyone on their toes, producing their best.
Posted: 10/8/2010 8:53:21 PM


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