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    Posted April 2, 2014 by
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    Russian GPS Failure (Glonass)

    Near midnight UTC between April 1st and April 2nd 2014 there was a complete failure of the Russian GNSS system for users. The orbit information being broadcast by the Glonass system was invalid and flagged as "Illegal ephemeris" for all SVs for a prolonged period of time. In order for a user to position themselves with GPS, the orbital location of each satellite being tracked must be known in order to compute the users position. Since the orbit information was not valid, it was not possible to compute a valid position using the Glonass system.

    It is possible this was some sort of selective availability test in order to deny the use of Glonass to non military users. If the orbit information was altered in a way that special military receivers could still decode the ephemeris messages but show up as "Illegal" to civilian users, then only the special military receivers would work.

    The attached image shows the period of time where Glonass orbit information was not valid, it was taken from the following web page:

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