U.S. To Stop Degrading GPS Signal

U.S. To Stop Degrading GPS Signal


by Frank Morring, Jr.

Aerospace Daily

05/01/00 05:43:45 PM U.S. EDT

The U.S. Air Force is scheduled tonight to switch off the software that degrades the Global Positioning System signal, giving everyone in the world access to the same basic signal the U.S. military uses to guide its precision weapons.

President Clinton approved elimination of GPS “selective availability” (SA) last Friday, after testing demonstrated the Pentagon can switch off the more precise signal during an armed conflict. The change is set for midnight GMT (8 p.m. EDT), and will upgrade civilian GPS receivers from an unaugmented accuracy of about 100 meters to roughly 10 meters.

“The decision to discontinue SA is coupled with our continuing efforts to upgrade the military utility of our systems that use GPS,” Clinton said in a statement issued yesterday. “The decision is supported by threat assessments which conclude that setting SA to zero at this time would have minimal impact on national security.”

Clinton gave the Pentagon 10 years to eliminate SA in a March 1996 directive, but the U.S. Space Command recently finished developing and testing a “ software fix” that will preserve the military utility of the system to U.S. forces engaged in combat by denying it their opponents.

“Think of it in a localized area,” Arthur L. Money, assistant defense secretary for command, control, communications and intelligence, told reporters at a White House briefing yesterday. “If your scenario is the Balkans...somebody in Berlin or Frankfurt or in Athens will not have a problem.” Money said the decision to deny GPS will be taken at the White House level.

Although the U.S. dropped SA as soon as it could, the move is unlikely to sway Europe's efforts to develop its own satellite-based system, given the new regional blackout capability. Nor did the White House decision impact the FAA's Wide Area Augmentation System (WAAS) program, which combines the GPS satellite signal with ground-based position signals for greater accuracy.

Eugene Conte, assistant secretary of transportation for policy, told reporters WAAS will continue to be needed for greater accuracy than even the unaugmented military signal can provide. However, an industry source suggested that it is “time to reevaluate the complexity of the WAAS program or even the need for it”

“Turning off SA is cause to reevaluate WAAS architecture because the reference stations may not be necessary any more, and it has a significant simplifying impact on the architecture,” the source continued.

Overall the U.S. spends about $500 million a year to maintain and upgrade the GPS signal, with another $120 million in spending set this year for the civilian augmentation systeems like WAAS, officials said