{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,21]],"date-time":"2026-02-21T07:43:38Z","timestamp":1771659818958,"version":"3.50.1"},"reference-count":38,"publisher":"MDPI AG","issue":"23","license":[{"start":{"date-parts":[[2019,11,24]],"date-time":"2019-11-24T00:00:00Z","timestamp":1574553600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In the Global Navigation Satellite System (GNSS) community, the Quasi-Zenith Satellite System (QZSS) is an augmentation system for users in the Asia-Pacific region. However, the characteristics and performance of four QZSS satellite clocks in a long-term scale are unknown at present. However, it is crucial to the positioning, navigation and timing (PNT) services of users, especially in Asia-Pacific region. In this study, the characteristics and performance variation of four QZSS satellite clocks, which including the phase, frequency, frequency drift, fitting residuals, frequency accuracy, periodic terms, frequency stability and short-term clock prediction, are revealed in detail for the first time based on the precise satellite clock offset products of nearly 1000 days. The important contributions are as follows: (1) It is detected that the times of phase and frequency jump are 2.25 and 1.5 for every QZSS satellite clock in one year. The magnitude of the frequency drift is about 10\u221218. The periodic oscillation of frequency drift of J01 and J02 satellite clocks is found. The clock offset model precision of QZSS is 0.33 ns. (2) The two main periods of QZSS satellite clock are 24 and 12 hours, which is the influence of the satellite orbit; (3) The frequency stability of 100, 1000 and 10,000 s are 1.98 \u00d7 10\u221213, 6.59 \u00d7 10\u221214 and 5.39 \u00d7 10\u221214 for QZSS satellite clock, respectively. The visible \u201cbump\u201d is found at about 400 s for J02 and J03 satellite clocks. The short-term clock prediction accuracy of is 0.12 ns. This study provides a reference for the state monitoring and performance variation of the QZSS satellite clock.<\/jats:p>","DOI":"10.3390\/s19235147","type":"journal-article","created":{"date-parts":[[2019,11,25]],"date-time":"2019-11-25T03:10:00Z","timestamp":1574651400000},"page":"5147","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":18,"title":["Characteristics and Performance Evaluation of QZSS Onboard Satellite Clocks"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6817-198X","authenticated-orcid":false,"given":"Wei","family":"Xie","sequence":"first","affiliation":[{"name":"College of Geology Engineering and Geomatics, Chang\u2019an University, 126 Yanta Road, Xi\u2019an 710054, China"}]},{"given":"Guanwen","family":"Huang","sequence":"additional","affiliation":[{"name":"College of Geology Engineering and Geomatics, Chang\u2019an University, 126 Yanta Road, Xi\u2019an 710054, China"}]},{"given":"Bobin","family":"Cui","sequence":"additional","affiliation":[{"name":"German Research Centre for Geosciences (GFZ), Telegrafenberg, 14473 Potsdam, Germany"},{"name":"Technische Universit\u00e4t Berlin, Str. des 17. Juni 135, 10623 Berlin, Germany"}]},{"given":"Pingli","family":"Li","sequence":"additional","affiliation":[{"name":"The 20th Research Institute of China Electronic, Technology Group Corporation, 1 Baisha Road, Xi\u2019an 710068, China"}]},{"given":"Yu","family":"Cao","sequence":"additional","affiliation":[{"name":"College of Geology Engineering and Geomatics, Chang\u2019an University, 126 Yanta Road, Xi\u2019an 710054, China"}]},{"given":"Haohao","family":"Wang","sequence":"additional","affiliation":[{"name":"College of Geology Engineering and Geomatics, Chang\u2019an University, 126 Yanta Road, Xi\u2019an 710054, China"}]},{"given":"Zi","family":"Chen","sequence":"additional","affiliation":[{"name":"College of Geology Engineering and Geomatics, Chang\u2019an University, 126 Yanta Road, Xi\u2019an 710054, China"}]},{"given":"Bo","family":"Shao","sequence":"additional","affiliation":[{"name":"The 20th Research Institute of China Electronic, Technology Group Corporation, 1 Baisha Road, Xi\u2019an 710068, China"}]}],"member":"1968","published-online":{"date-parts":[[2019,11,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2889","DOI":"10.1016\/j.asr.2018.01.020","article-title":"Atomic clock performance and combined clock error prediction for the new generation of BeiDou navigation satellites","volume":"63","author":"Wang","year":"2019","journal-title":"Adv. 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