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    Re: How likely is a GPS shutdown?
    From: Richard B. Langley
    Date: 2000 Jan 25, 10:24 AM

    PPS uses the encrypted P-code on both the L1 (same as civilian SPS) and the L2
    carrier. However, there are DoD single-frequency (L1) receivers and these
    also have SA and A/S decryption capability.
    -- Richard Langley
       Professor of Geodesy and Precision Navigation
    On Tue, 25 Jan 2000, Rodney Myrvaagnes wrote:
    >This is not quite right, although the rest of RBE's post is
    >right on. The military receivers that can get the encrypted
    >(long) word get it over another carrier than that used by
    >the C/A word decoded by civil receivers. There is no way
    >for your Walmart gps to use the military code.
    >During the Gulf War, SA was turned off because the military
    >had to use civilian receivers. SA was an afterthought,
    >applied because the civil receivers turned out to work much
    >better than expected.
    >On Mon, 24 Jan 2000 19:09:42 -0500, Richard B. Emerson
    >> >
    >> > 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
    >Rodney Myrvaagnes                   J36 Gjoa
    >Senior Editor           Electronic Products
    >My oyster knife is Y2K compliant
     Richard B. Langley                            E-mail: lang@unb.ca
     Geodetic Research Laboratory                  Web: http://www.unb.ca/GGE/
     Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506 453-5142
     University of New Brunswick                   Fax:      +1 506 453-4943
     Fredericton, N.B., Canada  E3B 5A3
         Fredericton?  Where's that?  See: http://www.city.fredericton.nb.ca/

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