Abstract
The remote synchronization system for the onboard crystal oscillator (RESSOX) realizes accurate synchronization between an atomic clock at a ground station and the QZSS onboard crystal oscillator, 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 geostationary earth orbit satellites (JCSAT-1B or Intelsat-4) to confirm that RESSOX is an excellent system for timing synchronization. JCSAT-1B, the elevation angle of which is 46.5 degrees at our institute, is little affected by tropospheric delay, whereas Intelsat-4, the elevation angle of which is 7.9 degrees, is significantly affected. The experimental setup and the results of uplink experiments and feedback experiments using mainly Intelsat-4 are presented. The results show that synchronization within 10 ns is realized.
Highlights
The Quasi-Senith Satellite System (QZSS) has been under development as a Japanese space project since 2003, and its mission is navigation and positioning [1]
We have developed a remote synchronization system for the onboard crystal oscillator (RESSOX), which does not require onboard atomic clocks
We have developed a feedback method that uses multiple navigation signals of the QZSS, and found that we do not need precise orbit information or any estimation of delays, such as those caused by the ionosphere and troposphere, to realize RESSOX technology
Summary
The Quasi-Senith Satellite System (QZSS) has been under development as a Japanese space project since 2003, and its mission is navigation and positioning [1]. Global navigation satellite systems (GNSSs), such as the GPS of the USA, GLONASS of Russia, GALILEO of Europe and COMPASS of China, are equipped with onboard atomic frequency standards that are used as the time reference This is because (1) atomic frequency standards have good midterm and long-term stability, (2) the orbit of satellites makes monitoring from only one ground station impossible, (3) these satellite systems are used for military missions and are expected to operate even if ground stations are destroyed, and (4) these systems consist of many satellites, making the continuous control of each satellite with many antennae difficult. Two GEO satellites, JCSAT-1B (elevation angle of 46.5 degrees as viewed from our institute) and Intelsat-4 (formerly PAS-4; elevation angle of 7.9 degrees as viewed from our institute), have been chosen as relay satellites because the elevation angle of the QZSS at Okinawa is expected to be between 10 and 90 degrees
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