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.
MARCH 29, 1999
BY DANIEL VERTON
AND BOB BREWIN
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