[IGSMAIL-2224] Information on GPS Satellites

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IGS Electronic Mail      Thu Apr  1 13:42:29 PST 1999      Message Number 2224
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Author: Ruth Neilan (forward)
Subject: Information on GPS Satellites

No effect on IGS operations or products...this action occured right before
week 1000.


Date:    3/30/99 6:55 AM


     MARCH 29, 1999 . . . 18:40 EST Federal Computer Week
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     DOD closes off GPS segment

     BY DANIEL VERTON (dan_verton at fcw.com)
     AND BOB BREWIN (antenna at fcw.com)

     The U.S. Space Command this month shut down a portion of the Global
     Positioning System signals available to civilian users, citing
     security reasons. The move comes on the heels of U.S. bombing
     operations in Kosovo and raises questions about how the military plans
     to share GPS access in the future.

     According to Richard Langley, a professor of geodesy and precision
     navigation at the University of New Brunswick, Canada, on March 5
     Spacecom stopped releasing so-called two-line orbital element sets for
     GPS satellites to civil users because the data is now considered too
     "sensitive" for public issue. According to Langely, the element sets
     have a number of different uses, including tracking the satellites'
     locations, determining when the signals from a particular satellite
     will be available at a particular location and planning observations.

     "The information on the GPS satellites has always been freely
     available via NASA's Goddard Space Flight Center, [at least] until a
     few weeks ago," Langley said. "The withdrawal of these two-line
     elements means that these users will have to find alternate [methods]
     of checking on the satellites," he said.

     The Defense Department already degrades the accuracy of civil GPS
     signals as a means to deny terrorists and other U.S. adversaries'
     precision targeting capabilities. Known as selective availability, the
     process seeks to maintain GPS support for DOD's navigation warfare
     needs while denying this capability to others. However, pressure has
     been growing throughout the civil and commercial sectors to terminate
     selective availability.

     Testifying last week before the Senate Armed Services Committee, Gen.
     Richard B. Myers, commander in chief of Spacecom, said DOD plans to
     discontinue Selective Availability at least by 2006. But Myers also
     said the Clinton Administration will revisit the issue each year
     beginning next year, making its decision based on recommendations from
     the Transportation Department and the CIA.

     "We must...continue to intelligently balance the needs of DOD with the
     needs of the civil GPS user community," said Myers. However, "as we
     attempt to balance the needs of all sectors for this emerging global
     commodity, we [also] must ensure our military forces retain a
     warfighting advantage," Myers said.



[Mailed From: "Ruth E Neilan" <Ruth.E.Neilan at jpl.nasa.gov>]