This page no longer updated from 31 October 2001. Latest version can be found at Transit

Program: Transit. Objective: Navigation.

Spin-stabilized Transit satellites were developed by the US Navy into the first operational navigation satellite system, for use by ballistic missile submarines and surface vessels. Early Transits carried a variety of piggy-back payloads, many still classified. Transit was also known as the Navy Navigation Satellite (NNS). Transit provided continuous navigation satellite service from 1964, initially for Polaris submarines and later for civilian use. Transit receivers used the known characteristics of the satellites orbit, measured the Doppler shift of the satellite's radio signal, and thereby calculated the receivers position on the earth. Individual satellites operated for over 10 years. Technical breakthroughs during the program included gravity gradient stabilization, the use of radio-isotope thermoelectric generators (RTG), and navigation satellite technologies used in the later GPS series. The TRIAD satellite was launched in 1972 to test improvements. Transit was superseded by the Navstar global positioning system. The use of the satellites for navigation was discontinued at the end of 1996, but the satellites continued transmitting and became the Navy Ionospheric Monitoring System (NIMS). Major Events: .

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Last update 12 March 2001.
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© Mark Wade, 2001 .