GPS satellites pass orbital milestone

A fleet of navigation satellites built by Lockheed Martin now has tallied a combined total of more than 50 years of successful operations in orbit.

The Global Positioning System (GPS) Block IIR spacecraft all were launched from Cape Canaveral Air Force Station aboard Boeing Delta 2 rockets. The satellites are an upgraded version of second-generation Navstar GPS satellites that began launching from Cape Canaveral on Feb. 14, 1989.

The first of the Block IIR spacecraft blasted off on July 23, 1997. Thirteen of the 28 GPS satellites now operating in orbit are Block IIR spacecraft.

GPS satellites provide precise navigation data to U.S. military troops and ships around the world as well as jet fighters, bombers and cargo planes. The satellites also emit a civilian signal that guides cars, trucks, boats, helicopters and commercial airliners, among other things.

Lockheed Martin holds a contract to deliver eight modernized GPS Block IIR spacecraft to the U.S. Air Force. The satellites provide enhanced encryption and anti-jamming capability for the military and a second civilian signal.

The first Block IIR-M was launched from the Cape last September. The second will be lofted later this year. The other six will be launched by the end of 2007.