Analysis of Influences of the Satellite Motion on Two-way Satellite Time Transfer via the Quasi-zenith Satellite (QZS)

Shoichiro Yokota, Yasuhiro Takahashi, Miho Fujieda, Jun Amagai, Kazuhiro Kimura and Shin'ichi Hama

Abstract:	The quasi-zenith satellite system (QZSS) is a Japanese integrated satellite service system for communication, broadcasting, and positioning for mobile users. One of the quasi-zenith satellites (QZSs) will be launched in 2008. The purpose of the satellite positioning system is to complement and augment GPS. Our developing time management system aims at real-time transferring of the QZSS time scale to all monitor stations and satellites for a highly accurate satellite positioning system. QZSS employs a two-way satellite time and frequency transfer (TWSTFT) technique to achieve the sub-nanosecond accuracy of the time management system. TWSTFT via the QZS has a problem, which is different from ordinary TWSTFT via communication satellites, or geostationary satellites, of attaining sub-nanosecond accuracy due to the QZS motion. Substantial motion of the satellite during the time between the satellite transmission and reception produces a nonreciprocal path in TWSTFT and thus degrades the time-transfer accuracy. We have analyzed the nonreciprocal geometric path due to the satellite motion, evaluated the TWSTFT accuracy and examined its correction by using a numerical three-dimensional model. A second of time difference produces microseconds of nonreciprocal geometric path delay. Our analysis demonstrates that correction of the nonreciprocal geometric path delay using the estimated QZS orbit that has 1-km accuracy reduces its residuals to the subnanosecond level.
Published in:	Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005) September 13 - 16, 2005 Long Beach Convention Center Long Beach, CA
Pages:	1704 - 1712
Cite this article:	Yokota, Shoichiro, Takahashi, Yasuhiro, Fujieda, Miho, Amagai, Jun, Kimura, Kazuhiro, Hama, Shin'ichi, "Analysis of Influences of the Satellite Motion on Two-way Satellite Time Transfer via the Quasi-zenith Satellite (QZS)," Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2005), Long Beach, CA, September 2005, pp. 1704-1712.
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