DENVER—The military did no advance testing on a specific type of military GPS receiver that had problems picking up locator signals after a change in ground-control software, the Air Force said Monday.
The Air Force tested other equipment, but none of it contained the type of receiver that was unable to lock on to Global Positioning System satellites after the change, said Joe Davidson, a spokesman for the Air Force Space and Missile Systems Center.
The manufacturer of the receivers, Trimble Advanced and Military Systems, said it ran its own advance tests using specifications from the Air Force GPS Wing and found no problems.
"Once the upgrade (on the ground-control software) went live, the compatibility problems were immediately identified and Trimble worked with the GPS Wing to resolve them," Trimble spokeswoman Lea Ann McNabb said in an e-mail.
Davidson said earlier that the problem, which occurred in January, was identified in less than two weeks. A temporary fix was installed in all the receivers and a permanent fix is being distributed, he said.
Davidson said the Air Force's testers didn't have any copies of the affected receiver before the problem. The Air Force is now acquiring a more representative sample of the tens of thousands of GPS receivers in use, he said.
Officials would not say how many weapons or other systems were affected by the problem, but they said operations were halted in only one program as a precaution.
They declined to identify the program, but an Air Force document briefly posted online last month indicated it was an unmanned Navy jet still under development.
The Air Force said the problem was caused by defective software in the Trimble GPS receivers. Trimble, a subsidiary of Sunnyvale, Calif.-based Trimble Navigation Ltd., received a $900,000 no-bid contract to help resolve the trouble.
The Global Positioning System uses 24 satellites beaming signals to Earth that can pinpoint a location using a receiver tuned to the satellite frequency. It's widely used by the military and in civilians gadgets like cell phones and car navigation systems.
The satellites are overseen by Air Force Space Command units at Schriever Air Force Base, Colo., and Los Angeles Air Force Base, Calif.
On Thursday, the Air Force plans to launch from Cape Canaveral Air Force Station, Fla., the first of a new generation of GPS satellites expected to last longer and perform better.
The new satellites, known as Block IIF, have a design life of 12 years, faster processors, more memory and a new signal for civilian uses. They are built by Boeing Co.