The role of time/frequency in navy navigation satellites

This paper discusses the role of time and frequency in three areas: 2) the operational Navy Navigation Satellite System, NNSS; 2) an experimental low-altitude navigation concept termed TIMATION; 3) proposals for advanced navigation satellites. These operating, experimental, and proposed systems all use concepts which allow the user to remain passive. The operational NNSS system uses the Doppler technique to establish user positions to ~100 m. In this concept, the frequencies received from the satellite are compared to the frequencies generated in the user equipment. One can also compare the time a signal arrives from a satellite clock to a time generated in the user equipment clock for passive ranging. The paper shows that this passive ranging problem is easily transformed to the celestial navigation problem. Extension of these techniques allows one to use satellites as clock transporters and hence to compare clocks located throughout the globe to 0.5 µs. Experimental results are shown. It has been possible to determine the effects of radiation on quartz crystals and to determine that this effect is due principally to protons. System concepts are described which show this clock/time technique can determine user position, velocity, and time continuously, accurately, and globally.