Two-Way Satellite Time Transfer Using Low Power CW Tones

C.C. Costain, H. Daams, J.S. Boulanger

Abstract:	In the search for an economical means of precise time transfer, the NRC Time Laboratory decided to adapt, for time transfer, the techniques used by radio astronomers in an experiment to compare the phases of the local oscillators at widely separated VLBI stations. The objective is to design a system which would use commercial satellites, and which would be of reasonable cost for the ground stations and for operations. Two satellite ground stations have been installed at NRC about 100 m from the Time Laboratory. The antennas are 3 m in diameter, and the transmitter power is 1W. For the preliminary experiment, a channel on the Anik A1 6/4 GHz satellite was made available by Telesat Canada. Two tones were transmitted 4 16 MHz from the suppressed carrier. The difference frequency of 32 MHz was recovered using narrow band receivers. A low level 1 MHz phase modulation was added to identify the 32 MHz cycle, giving 1 vs ambiguity in the time transfer. With less than 1/4 W in each tone, the EIRP is 43 dB below that of a normal TV earth station, and no frequency dispersion is required. The measurements taken each second for the 32 MHz have an rms scatter of 1 ns. The transponder of the failing Anik A1 (now out of service) was 15 dB down on normal performance, so that much better results are expected on the Anik A3 later this year.
Published in:	Proceedings of the 14th Annual Precise Time and Time Interval Systems and Applications Meeting November 30 - 3, 1982 NASA Goddard Space Flight Center Greenbelt, Maryland
Pages:	31 - 37
Cite this article:	Costain, C.C., Daams, H., Boulanger, J.S., "Two-Way Satellite Time Transfer Using Low Power CW Tones," Proceedings of the 14th Annual Precise Time and Time Interval Systems and Applications Meeting, Greenbelt, Maryland, November 1982, pp. 31-37.
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