Precise ETS-VIII Orbit Determination and Clock Synchronisation Using GPS-Like Navigation Signals

Yanming Feng and Akinobu Suzuki

Abstract:	Engineering Testing Satellite -VIII (ETS-VIII) is a NASDA's Geostationary satellite, scheduled to be launched in 2003. ETS-VIII will carry a heavy Caesium atomic clock to provide high accuracy reference frequency to control the satellite time and generate GPS- like navigation signals on board the spacecraft. With the High Accuracy Clock (HAC) payload, NASDA aims to test and develop a number of basic technologies necessary for implementation of GPS-like space-based positioning missions in the future, including an atomic clock for space use, high accuracy time synchronisation and high accuracy orbit determination [1]. Four ground stations equipped with HAC/GPS receiver sets will be tentatively located in Bangkok, Brisbane, Musuda and Tsukuba respectively. A joint research program on the above experiment has been arranged between Japanese NASDA and Australian CRCSS. The latter will also be responsible for the operation of the ground monitor station in Brisbane. The experiment provides a unique opportunity for Australian and Japanese scientists to test precise orbit and clock determination of high altitude satellite with the inverse GPS techniques. This paper examines the estimation techniques for ETS-VIII clock and orbit parameters using ETS-VIII navigational signals and GPS measurements from the network of 4 HAC/GPS receiver sets. Inverse GPS positioning techniques are presented with an emphasis on the GPS data processing strategies for receiver clock solutions. For assumptions of ETS-VIII code range error of 0.10m and different levels of uncertainty for ground clock synchronisation, covariance analysis has been conducted to demonstrate the achievable orbit and clock accuracies with different estimation options. Numerical results show that with 24-hour tracking data from the planned 4 monitor stations, the 3D ETS-VIII orbit rms accuracy can be improved via a dynamical filtering from over 400 m to a few metres, and the clock rms accuracy of from 1.5 msec to 5 nsec. Decimetre-level orbit/ 1 nsec-level clock solutions are also achievable if HAC and GPS data are processed precisely in post mission on a daily basis, with high-rate clock outputs.
Published in:	Proceedings of the 2001 National Technical Meeting of The Institute of Navigation January 22 - 24, 2001 Westin Long Beach Hotel Long Beach, CA
Pages:	734 - 741
Cite this article:	Feng, Yanming, Suzuki, Akinobu, "Precise ETS-VIII Orbit Determination and Clock Synchronisation Using GPS-Like Navigation Signals," Proceedings of the 2001 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 2001, pp. 734-741.
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