|Throughout the 1960s the U.S.
Navy and Air Force worked on a number of systems that would provide navigation capability
for a variety of applications. Many of these systems were incompatible with one another.
In 1973 the Department of Defense directed the services to unify their systems. The basis
for the new system would be atomic clocks carried on satellites, a concept successfully
tested in an earlier Navy program called TIMATION. The Air Force would operate the new
system, which it called the Navstar Global Positioning System. It has since come to be
known simply as GPS.
The new system called for three components: ground stations that controlled the system, a "constellation" of satellites in Earth orbit, and receivers carried by users. The system was designed so that receivers did not require atomic clocks, and so could be made small and inexpensively.
The Soviet Union also developed a satellite-based navigation system, called GLONASS, which is in operation today.
GPS satellite launches began in 1978, and a second-generation set of satellites ("Block II") was launched beginning in 1989. Today's GPS constellation consists of at least 24 Block II satellites. The system became fully operational in 1995.
right: 1/4 scale model GPS
Satellite, donated by Rockwell International Corporation, on display in the National Air
and Space Museum.
|MANPACK GPS Receiver
One of the first portable GPS units available to soldiers in the field was the PSN-8 "Manpack" receiver. About 1,400 were manufactured between 1988 and 1993.
Manpack on display in the Museum exhibition was
lent by the National Museum of American History.
|PLGR GPS Receiver
The Manpack was replaced in 1993 by the hand-held Precision Lightweight GPS Receiver (PLGR), popularly known as the "Plugger." These units are similar to civilian receivers, but they can use higher-precision GPS signals.
Image courtesy Rockwell Collins.
GPS Goes Public
After the downing of Korean Flight 007 in 1983 -a tragedy that might have been prevented if its crew had access to better navigational tools- President Ronald Reagan issued a directive that guaranteed that GPS signals would be available at no charge to the world. That directive helped open up a commercial market.
Deployment of GPS continued at a steady pace through the 1990s, with growing numbers of civilian and military users. GPS burst into public awareness during the Persian Gulf War in 1991. GPS was used extensively during that conflict, so much so that not enough military-equipped GPS receivers were available. To satisfy demand, the Department of Defense acquired civilian GPS units and temporarily changed GPS transmissions to give civilian receivers access to higher-accuracy military signals.
Before GPS | GPS Revolution | How GPS Works | Land and Sea Navigation
Navigation In The Air | Mapping The Earth | Managing The Land | New Frontiers in Science
GPS: A New Constellation
National Air and Space Museum