Timation

Abstract: 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.

Abstract: During 1972 time transfer experiments were run between the US Naval Observatory and the Royal Greenwich Observatory and, in 1973, between the US Naval Observatory and the Division of National Mapping in Canberra, Australia In both cases the time transfer agent was the TIMATION 2 satellite, 1969-82B The satellite ephemerides were computed from data provided by the Defense Mapping Agency TRANET This net tracked the satellite's Doppler transmissions The phase of the satellite clock was determined from knowledge of the position of the satellite and of the observer and the computed distance between the two By monitoring the clock on successive passes the rate of the satellite clock was determined at Washington By again monitoring the satellite clock at the distant station the satellite clock could be compared to the local clock and this local clock compared to the US Naval Observatory clocks In 1972 the RMS of observations at Greenwich deviated by approximately 1/4 microsecond from a straight line when compared to the Naval Observatory In 1973 the observation errors at Canberra were approximately half as great

Abstract: Laser ranging systems, their range and accuracy capabilities, and planned improvements for future systems are discussed, the systems include one fixed and two mobile lasers ranging systems. They have demonstrated better than 10 cm accuracy both on a carefully surveyed ground range and in regular satellite ranging operations. They are capable of ranging to all currently launched retroreflector equipped satellites with the exception of Timation III. A third mobile system is discussed which will be accurate to better than 5 cm and will be capable of ranging to distant satellites such as Timation III and LAGEOS.