4 - 8 - 2 Time Comparison Equipment for ETS - VIII 4 - 8 - 2 — Data Processing , Analysis and Capability of Time Comparison —

The Engineering Test Satellite VIII (ETSVIII), scheduled for launch in 2004, has been developed to expand the advanced fundamental technologies required in future space exploitation, including mobile communications technology and high-precision satellite positioning technology [1]. This will be the first Japanese satellite to be equipped with an onboard atomic clock (the High Accuracy Clock: HAC) for use in the establishment of the basic technologies of a satellite positioning system. The Communications Research Laboratories (CRL) has developed Time Comparison Equipment (TCE) for time transfer between the atomic clocks on the satellite and on the ground, and plans to evaluate the characteristics of the atomic clock in orbit. The TCE and the TCE earth station will conduct two-way time transfer between the atomic clocks on the satellite and on the ground. TCE and TCE earth station are designed to process data simultaneously to enable correction of the problematic delays in time transfer; namely, the fluctuation in equipment delay and in delay due to the terrestrial ionosphere. This correction is expected to provide higher overall precision in time transfer. The data collected by the TCE and TCE earth station are transferred to the data-processing units installed in the earth station, where correction and time-transfer processing is then performed. This paper presents the configuration of the TCE and the principles of time transfer in Section 2, the details of the process in the data-processing unit in Section 3, and the