GPS glitch hit some military systems in January

By Dan Elliott
Associated Press Writer / May 14, 2010

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DENVER—A software glitch in the military GPS network temporarily left some defense systems unable to lock onto locator signals from satellites in January, but the problem has been fixed, the Air Force said Friday.

The Air Force declined to say how many weapons or other systems were affected, but it said operations were halted in only one program as a precaution. Officials declined to identify the program. reported this month that the Navy interrupted development work on an unmanned jet because of the problem. The website cited an Air Force contract document that was posted online and later removed.

Joe Davidson, a spokesman for the Air Force Global Positioning Wing, said in an e-mail to The Associated Press that no civilian GPS functions were affected.

He said up to 10,000 military GPS receivers manufactured by Trimble Advanced and Military Systems could have been affected, but he declined to give a specific number.

It wasn't clear whether each of those receivers is in a separate piece of equipment or weapon. It also wasn't clear how many other GPS receivers from other manufacturers are used by the military.

Trimble spokeswoman Lea Ann McNabb said the company's technical staff worked with the Air Force to fix the problem. She referred all questions to the Air Force.

The GPS system uses a constellation of 24 satellites beaming down signals that receivers can use to pinpoint the receiver's location. GPS is used in everything from handheld units for hikers and dashboard models for civilian drivers to military aircraft and artillery shells.

The satellites are overseen by Air Force Space Command units at Schriever Air Force Base, Colo., and Los Angeles Air Force Base, Calif.

The glitch occurred when new software was installed in ground control systems on Jan. 11. Some GPS receivers soon experienced trouble locking in on the satellite signals, Davidson said.

The GPS Wing and Trimble identified the problem in less than two weeks and began installing a temporary fix, Davidson said. A permanent fix has been developed and is being distributed, he said.

Trimble received a $900,000, no-bid contract to help identify and fix the problem.

Davidson said the problem was caused when the military altered some message bits in the GPS signal, which affected how the receivers operated. He said the message bits involved are used only by the military.

SpaceNews reported that the Air Force contract document said the Navy halted work on its X-47B unmanned jet because of the software problem. The X-47B is designed to take off and land on aircraft carriers for reconnaissance, surveillance and targeting missions. Its first flight is expected later this year.

The contract document said the delay was costing $1 million a day, but it's not clear how long it lasted.

SpaceNews said the contract document was posted on the Federal Business Opportunities website on April 30 but was removed by May 3.

The contract document also said the Army stopped using its GPS-guided Excalibur artillery rounds because of the problem. Davidson told the AP the Excalibur did have a problem, but it turned out to be different from the one caused by the software change.

He declined to say what the problem was but said it has been solved.

The Army says Excalibur shells can land to within about 10 yards of a target 14 miles away. They have been used in Afghanistan and Iraq.