Defense Advanced Research Projects AgencyTagged Content List

Position, Navigation and Timing

Technologies relating to precision geolocation, time-keeping and synchronization

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ARPA launched the first satellite in what would become the world's first global satellite navigation system. Known as Transit, the system provided accurate, all-weather navigation to both military and commercial vessels, including most importantly the U.S. Navy’s ballistic missile submarine force.

Transit, whose concept and technology were developed by Johns Hopkins University Applied Physics Laboratory, established the basis for wide acceptance of satellite navigation systems. The system's surveying capabilities—generally accurate to tens of meters—contributed to improving the accuracy of maps of the Earth's land areas by nearly two orders of magnitude.

ARPA funded the Transit program in 1958, launched its first satellite in 1960, and transitioned the technology to the Navy in the mid-1960s. By 1968, a fully operational constellation of 36 satellites was in place. Transit operated for 28 years until 1996, when the Defense Department replaced it with the current Global Positioning System (GPS).