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    Re: Is Celestial Navigation really a backup to GPS Navigation?
    From: Roger W. Sinnott
    Date: 2018 Sep 10, 19:53 -0400



    Another possibility, or even high likelihood, is that in time of war the U.S. military would re-impose “selective availability” -- the intentional degradation of GPS accuracy when accessed by civilians.  I imagine they might want to do this well before an all-out war broke out, when the prospect was looming.  They could also, I’m sure, degrade GPS much more than was done routinely before 2000, or even turn it off completely (except to the U.S. military itself).   




    ------- Brad Morris wrote ---------

    There is one scenario in which a systemic "failure" of the GPS based satellite system becomes a extremely likely outcome.


    War. . . .


    Short of a major conflict between the mentioned principles, I can think of no scenario in which a systemic failure of the satellite system occurs.  Even if several of the 30 satellites become simultaneously degraded or broken, the level of system redundancy insures continued positioning availability.


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