Actual Operation Simulation of RESSOX Ground Experiments

Toshiaki Iwata, Kumiko Machita, Takashi Matsuzawa

Abstract:	The first quasi-zenith satellite (QZS) of Japan, named “Michibiki,” was launched on 11 September 2010. After 3 months of initial functional verification tests, the actual operation will start. We have planned three kinds of experiments using Michibiki: (1) experiments without voltage-controlled oven-compensated controlled crystal oscillator (VCOCXO) control of Experiment One, (2) experiments with VCOCXO control of Experiment One, and (3) experiments with VCOCXO control of Experiment Two. In Experiment One, the remote synchronization system of the onboard crystal oscillator (RESSOX) control signal that includes information of the standard time will be sent from ground stations, and the onboard crystal oscillator of Michibiki will be controlled to synchronize the arrival of the RESSOX control signal. The RESSOX control signal is similar to such time calibration signals as WWV or JJY, but the delay is compensated. In Experiment Two, on the basis of the results of a time comparison experiment between the onboard crystal oscillator and the ground standard time conducted by the National Institute of Information and Communications Technology (NICT), the voltage applied to the onboard crystal oscillator will be calculated at the ground station and transmitted to Michibiki to control the crystal oscillator. The effects of some data and command delays on control quality and performance in an actual operation are considered as well. For example, in Experiment One, every 30 s, we expect to receive orbit forecast information in the International Terrestrial Reference Frame (ITRF) for a duration of 3minutes, which is almost real time, from the Master Control Station. We estimate that the data will take one and a half minutes to reach us as the satellite orbit is measured. In this regard, the available data will be one and a half minutes. We also expect to experience some discontinuities when we use the following data every 30 s. In Experiment Two, approximately 20 s is required from the start of time comparison to the voltage command execution. A large applied voltage change (i.e., sudden frequency change of satellite time standard) may lead to loss of time comparison signal at Michibiki and this may cause loss of time comparison data. We set these conditions in the ground experiments, investigate their effects, and propose countermeasures.
Published in:	Proceedings of the 42nd Annual Precise Time and Time Interval Systems and Applications Meeting November 15 - 18, 2010 Hyatt Regency Reston Town Center Reston, Virginia
Pages:	141 - 160
Cite this article:	Iwata, Toshiaki, Machita, Kumiko, Matsuzawa, Takashi, "Actual Operation Simulation of RESSOX Ground Experiments," Proceedings of the 42nd Annual Precise Time and Time Interval Systems and Applications Meeting, Reston, Virginia, November 2010, pp. 141-160.
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