ABSTRACT
The US Navy Navigation Satellite System (NNSS), alternatively known as Transit, was developed for the US Navy between 1958 and 1963 by the Applied Physics Laboratory of the Johns Hopkins University. It became available to non-military users in 1967. The system consists of several orbiting satellites and a network of tracking stations which monitor the satellites, and at intervals update their transmitted information. Use is made by the receiving apparatus of the observed Doppler shift of the satellite’s transmission frequency to determine the relative velocity between the satellite and the receiver. From its transmitted data, a passing satellite’s orbit is precisely determined. From this, and the rate of change of range to the satellite derived from the Doppler shift, the position of the receiver can be accurately computed.
