Subjects: Astronomy submitted time 2023-10-07 Cooperative journals: 《天文学报》
Abstract： In order to improve the reliability of the time transfer link, Bureau International des Poids et Mesures (BIPM) has officially taken the Galileo time comparison as the backup link for UTC calculation since 2020. Therefore, the delay calibration of the Galileo signal of the receiver is a necessary work for all time-keeping labs around the world to participate in the UTC link. Taking the GPS link calibrated by Physikalisch-Technische Bundesanstalt (PTB) and the National Time Service Center (NTSC) as a reference, this paper sets PT09 receiver as a reference station to calibrate and verify the total Galileo E3 (Galileo E1\&E5a) delay of NT02 and NT05 receivers of NTSC. The results show that the total Galileo E3 delays of NT02 and NT05 are 74.6\;ns and 46.5\;ns respectively, the calibration uncertainty is 3.5\;ns, and the calibration delay is relatively stable. After calibration, the results of GPS P3 and Galileo E3 common view comparison between NT02 and NT05 receivers of NTSC and calibrated receivers of other time-keeping labs are basically consistent. Taking the comparison results of GPS P3 links between NTP3 and receivers of other labs as a reference, the average deviation is less than 1.5\;ns, which is within the calibration uncertainty.
Subjects: Astronomy >> Astrophysical processes submitted time 2022-11-22 Cooperative journals: 《天文研究与技术》
Abstract： Timekeeping atomic clocks mainly include hydrogen masers and cesium atomic clocks. In order to further explore the time-scale performance of different types of timekeeping atomic clocks, this paper carried out a study on the hydrogen maser and the hydrogen-cesium combined time scale . Firstly, the hydrogen maser was classified according to the d bulletin issued by BIPM. According to the classification results, the atomic time-scale theory is used to calculate the hydrogen maser time scale, and the analysis results are given. Then the time scales of cesium clocks are calculated and two different time scales of hydrogen-cesium combined ensembles are analyzed and explored. The results show that the time-scale fluctuation range of the hydrogen maserensemble based on the small frequency drift is smaller, and the stability is better than the time scale of the hydrogen maserensemble based on the larger frequency drift. The time scale stability of the hydrogen-cesium combination is better than the total cesium clock, and the result of different hydrogen-cesium combination time scale clocks are similar.
Subjects: Astronomy >> Astrophysical processes submitted time 2022-11-01 Cooperative journals: 《天文研究与技术》
Abstract： Time-frequency data resources are important national information resources. The design of the time-frequency data platform relies on the time-frequency data generated by the daily operation of the National Time Service Center, the bulletin issued by Bureau International Des Poids et Mesures (BIPM) and International Earth Rotation and Reference Systems Service(IERS).The data platform can provide abundant data resources for the research of time-keeping technology. This paper first introduces the construction of the time-frequency data platform, and then uses the local time-keeping system comparison and long-distance link comparison data collected by the data platform to carry out time-keeping technology research, including the evaluation of the state of the atomic clock, and the analysis of the abnormal jump of the atomic clock. For different types of clock keeping, analyze and compare the performance indicators of atomic clocks such as fluctuation and stability, and conduct clock error prediction research based on the ARIMA model. The research contents of those different aspects can provide important reference for the continuous and reliable operation of the time-keeping system.
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