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    Re: How likely is a GPS shutdown?
    From: Richard B. Emerson
    Date: 2000 Jan 24, 5:10 PM

    Luis Soltero writes:
     > I was under the impression that the GPS satellite network still
     > belongs and is managed by the military.
    Primarily, yes, but not entirely.  Dept. of Commerce is a player,
     > So, let me ask the obvious.  What
     > happens when the US gets involved in a skirmish or a war
     > and decides that it would be in our best interest to disable
     > the civilian GPS system depriving the enemy of the use
     > of those wonderfully accurate $150 hand held positioning
     > devices.
     > I suspect that the military has its own encrypted version
     > of GPS although this is simply a guess on my part.
    One of the absurdities of GPS is that during Desert Storm and Panama,
    GPS' selective availability was turned off.  Thus, for a short period,
    the normally encrypted data segment (it's already there and used
    routinely) was available unencrypted.  Consider, too, the error even
    with S/A enabled.  A fuel-air bomb (or ammonium nitrate bomb) could
    miss its aiming point by a few hundred feet and still do serious
    damage.  The only place where pinpoint accuracy really counts is
    striking hardened targets (e.g., missile silos) and for most "basement
    bomber" terrorists, this isn't a primary target.
     > Once the FAA adopts GPS as its primary
     > navigational system disabling civilian GPS will be
     > much more difficult.
     > Given the above scenario I would expect the likely
     > hood of a GPS shutdown to be exactly equal the
     > likely hood of a skirmish and/or war.  i.e. fairly high.
    Wrong.  We've been through several military actions (e.g., Bosnia) and
    GPS hasn't dropped off line.  Truth is, anything less than major war
    is not likely to pose a problem for casual GPS users.  What is more
    likely to pose a problem is local receiver failure, not GPS failure.
    Nonetheless, the specter of DoD taking GPS offline has adversely DoC
    attempts to sell GPS-based commercial aircraft landing systems.
    Non-US carriers don't want have their aircraft and passengers held
    hostage by DoD.  Also, keep in mind there's GLONASS and the EU is
    working on a system so that in maybe 5-10 years there may well be
    three systems to choose from.
    S/V One With The Wind, Baba 35

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