Japan's Quasi-Zenith Satellite System (QZSS) is scheduled for launching in 2010. We have been conducting research on the remote synchronization system for the onboard crystal oscillator (RESSOX), which does not require onboard atomic clocks, for the QZSS since 2003. RESSOX reduces overall cost and satellite power consumption, as well as onboard weight and volume, and is expected to have a longer lifetime than a system with onboard atomic clocks. Since a QZSS does not yet exist, we have been conducting synchronization experiments using current geostationary satellites (JCSAT-1B or IS-4 [formerly PAS-4]) to confirm that RESSOX is an excellent system for timing synchronization. For the experiments using JCSAT-1B, we have already reported that synchronization within 10 ns was achieved when feedback information was used. Since JCSAT-1B was located at an elevation angle of 46.5 degrees at our institute, however, the effect of tropospheric delay was not very large. To examine the applicability of RESSOX under more severe conditions, IS-4 was selected. IS-4 is located at an elevation angle of 7.9 degrees at our institute, which means that the effect of tropospheric delay is large (in the case of the QZSS, the smallest elevation angle at Okinawa station is approximately 10 degrees). In this paper, we will present the experimental setup, the results of uplink experiments and feedback experiments, and some discussions on the use of RESSOX with the QZSS.
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