The last in a series of eight Lockheed Martin-built GPS 2R satellites modernized for better performance has been declared operational by the U.S. Air Force for military and civilian users, the Newtown, Pa.-based contractor said in a Sept. 3 press release.

The satellite, known as GPS 2R-21M, was launched Aug. 17 from Cape Canaveral Air Force Station, Fla., atop a United Launch Alliance Delta 2 rocket.

A separate GPS 2R satellite launched in March has not yet been declared operational due to a problem with a payload, dubbed L5, that was added to the satellite to reserve frequencies to be used by future GPS craft.

“That satellite is undergoing extensive, comprehensive testing with both civilian and military receivers and is expected to be set healthy for users when testing is complete, currently projected for October,” Lockheed Martin spokesman Steve Tatum said Sept. 4.