April 26, 1980
The first GPS satellite to carry Integrated Operational Nuclear Detonation Detection System (IONDS)
sensors is launched.

1982
A decision to reduce the GPS satellite constellation from 24 to 18 satellites is approved by DoD following a major program restructure brought on by a 1979 decision by the Office of the Secretary of Defense to cut $500 million (approximately 30 percent) from the budget over the period FY81–FY86.

July 14, 1983
The first GPS satellite to carry the newer Nuclear Detonation Detection System (NDS) is launched.

September 16, 1983
Following the Soviet downing of Korean Air flight 007, President Reagan offers to make GPS available for use by civilian aircraft, free of charge, when the system becomes operational. This marks the beginning of the spread of GPS technology from military to civilian aircraft.

April 1985
The first major user equipment contract is awarded by the JPO. The contract includes research and
development as well as production options for 1-, 2-, and 5-channel GPS airborne, shipboard, and
manpack (portable) receivers.

1987
DoD formally requests that the Department of Transportation (DoT) assume responsibility for
establishing and providing an office that will respond to civil user needs for GPS information, data, and
assistance. In February 1989, the Coast Guard assumes responsibility as the lead agency for the Civil
GPS Service.

1984
Surveying becomes the first commercial GPS market to take off. To compensate for the limited number of satellites available to them early in the constellation’s development, surveyors turned to a number of GPS accuracy enhancement techniques including differential GPS and carrier phase tracking.

March 1988
The Secretary of the Air Force announces the expansion of the GPS constellation to 21 satellites plus
3 operational spares.

February 14, 1989
The first of 28 Block II satellites is launched from Cape Canaveral AFS, Florida, on a Delta II booster. The Space Shuttle had been the planned launch vehicle for the Block II satellites built by Rockwell. Following the 1986 Challenger disaster, the JPO reconsidered and has since used the Delta II as the GPS launch vehicle.
Selective availability (SA) and anti-spoofing (AS) become possible for the first time with the Block II
design.

June 21, 1989
Martin Marietta (after buying out the General Electric Astro Space division in 1992) is awarded a contract to build 20 additional “replenishment” satellites (Block IIR). The first Block IIR satellite will be ready for launch as needed at the end of 1996.