Remote Clock Synchronization System Using Geostationary Satellite for Japanese Quasi-Zenith Satellite System

N. Takasaki, A. Iwasaki, T. Iwata, M. Imae, T. Suzuyama

Abstract:	Synchronization of the voltage-controlled crystal oscillator (VCXO) to the ground atomic clock within an error of 10 ns was achieved in experiments of the remote synchronization system for onboard crystal oscillators (RESSOX) using a geostationary satellite. RESSOX, which is a new satellite time-keeping system planned for the Japanese Quasi-Zenith Satellite System (QZSS), maintains time reference only with the onboard VCXO that is continuously synchronized to the ground atomic clock. In the experiments, the VCXO of the satellite site was linked to the atomic clock of the ground site via the geostationary satellite. Time signals of references were transmitted from each site to the geostationary satellite, which was used as a mirror to reflect signals from each site back to another. The objectives of this study were to evaluate RESSOX with consideration of actual delays in outer space, and to synchronize the VCXO to the atomic clock within an error of 10 ns. The experiment was divided into three phases. In the first phase, preliminary experiments were conducted to determine the propagation time, TPR, to and from the geostationary satellite, and to compare it with the estimated TPR computed with our simulators beforehand. The estimation error was between 4,700 to 4,800 ns, and was mostly due to instrumental constants. In the second phase called uplink experiments, the VCXO was controlled only with the feed-forward loop, the object of which was to compensate the actual TPR using the estimated TPR as command. However, since the estimation error remained in the clock error of the VCXO and the atomic clock, the feedback loop of the estimation error in downlink signal was considered in end-to-end experiments, and the VCXO was synchronized to the atomic clock within an error of 10 ns, proving the potential of RESSOX.
Published in:	Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006) September 26 - 29, 2006 Fort Worth Convention Center Fort Worth, TX
Pages:	2120 - 2130
Cite this article:	Takasaki, N., Iwasaki, A., Iwata, T., Imae, M., Suzuyama, T., "Remote Clock Synchronization System Using Geostationary Satellite for Japanese Quasi-Zenith Satellite System," Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006), Fort Worth, TX, September 2006, pp. 2120-2130.
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