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Research on remote synchronization system for onboard crystal oscillators of quasi-zenith satellite system

The remote synchronization system for the onboard crystal oscillator (RESSOX) of the quasi-zenith satellite system (QZSS) has been studied at AIST since 2003. RESSOX reduces the overall cost and satellite power consumption, the onboard weight and volume, and has a longer lifetime than a system with an onboard atomic time standard. The targets of our research are synchronization to within 10 ns between the ground station time standard and the onboard QZSS crystal oscillators and stability better than 1×1013 at 100,000 s. RESSOX has been developed in four stages: (1) arrangement of hardware simulators and feasibility study, (2) QZSS experiment preparation, (3) RESSOX algorithm development, and (4) space experiments using geostationary satellites. After launch in 2010, one more stage will be added: (5) demonstration of RESSOX using QZSS. The achievements in the first four stages and a plan of the final stage will be summarized.