Saya Matsushita, Hiroshi Takiguchi, Toshitaka Sasaki, Hideki Yamada, Isao Kawano, Koichi Inoue, Japan Aerospace Exploration Agency (JAXA), Japan; Yuichi Takeuchi, Mitsuru Musha, The University of Electro-Communications, Japan

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Abstract:

Satellite clocks play an important role of satellite navigation system, because positioning and navigation using Global Navigation Satellite System (GNSS) are based on ranging measurements of the transmission time of signals from satellites to receivers. There are various sources of errors in ranging measurements, for example, one of them is caused by the error of satellite clocks. Therefore, satellite clock stability is key technology to reduce the ranging measurements errors. Current GNSS carry atomic clocks, however, optical clocks which are much higher frequencies than THz and more stable than the atomic clocks have been developing over the last decades. Furthermore, the iodine-based optical clock which uses an iodine-stabilized laser in combination with an optical frequency comb has the possibility to apply for space crafts. Both iodine frequency reference and optical frequency comb have been launched by sounding rockets. For Precise Point Positioning (PPP), additional information is required such as satellite precise orbit and clock corrections from precise ephemeris, usually IGS products. The accuracy of IGS final products is a few centimeters and influenced by the limitation of clock modelling. A highly stable clock such as optical clocks can support Precise Orbit and clock Determination (POD) to reduce estimated clock modelling errors. In addition, radial orbit errors compensated by satellite clock corrections would be also improved. Thus, if GNSS have more stable clocks, the accuracy of POD would be improved. JAXA simulated POD in the case that Quasi Zenith Satellite System (QZSS) carries the Rubidium Atomic Frequency Standards (RAFS) and the iodine-based optical clock. In this paper, we evaluated the effect of the optical clocks for satellite navigation system, focusing on QZS-1.