{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,20]],"date-time":"2026-02-20T16:45:34Z","timestamp":1771605934430,"version":"3.50.1"},"reference-count":33,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2022,12,26]],"date-time":"2022-12-26T00:00:00Z","timestamp":1672012800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100015014","name":"National Time Service Center, Chinese Academy of Sciences (CAS)","doi-asserted-by":"publisher","award":["E167SC14"],"award-info":[{"award-number":["E167SC14"]}],"id":[{"id":"10.13039\/501100015014","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100015014","name":"National Time Service Center, Chinese Academy of Sciences (CAS)","doi-asserted-by":"publisher","award":["12203059"],"award-info":[{"award-number":["12203059"]}],"id":[{"id":"10.13039\/501100015014","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100015014","name":"National Time Service Center, Chinese Academy of Sciences (CAS)","doi-asserted-by":"publisher","award":["12073034"],"award-info":[{"award-number":["12073034"]}],"id":[{"id":"10.13039\/501100015014","id-type":"DOI","asserted-by":"publisher"}]},{"name":"National Natural Science Foundation of China","award":["E167SC14"],"award-info":[{"award-number":["E167SC14"]}]},{"name":"National Natural Science Foundation of China","award":["12203059"],"award-info":[{"award-number":["12203059"]}]},{"name":"National Natural Science Foundation of China","award":["12073034"],"award-info":[{"award-number":["12073034"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The augmentation of the Global Navigation Satellite System (GNSS) by Low Earth Orbit (LEO) satellites is proposed as an effective method to improve the precision and shorten the convergence time of Precise Point Positioning (PPP). Serving as navigation satellites in the future, LEO satellites need to be provided with their high-accuracy orbits in real-time. This would potentially enable the high-accuracy real-time LEO satellite clock determination, and eventually facilitate the high-accuracy ground-based positioning. Studies have been performed to achieve such real-time orbits using a Kalman filter in both the kinematic and reduced-dynamic modes. Batch Least-Squares (BLS) adjustment delivers more stable orbits in near-real-time, as it performs better phase screening. However, it suffers from longer delays compared to the Kalman filter. With the LEO satellite orbit prediction strategies improved over time, this latency can be bridged by short-term orbit prediction. In this study, using real-time GNSS satellite products, the real-time LEO satellite orbits are obtained based on the batch least-squares adjustment and short-term prediction. LEO ephemeris parameters are generated within specific prediction time windows. Using real data from the 500 km GRACE C satellite and 810 km Sentinel-3B satellite, the near-real-time BLS Precise Orbit Determination (POD) results exhibit good accuracy with an Orbital User Range Error (OURE) of 2\u20134 cm using different real-time GNSS products. A range of delays of the BLS POD processes are assumed, based on tests performed on different processing machines, leading to various prediction windows, from 3\u20138 min to 12\u201317 min that correspond to the real-time usage. The orbital prediction errors are shown to be highly correlated with the orbital height and the prediction time. The computational efficiency thus becomes essential to reduce the prediction errors for a certain LEO satellite. For advanced processing units leading to a prediction window shorter or equal to 6\u201311 min, one can expect a total real-time orbital error budget of 3\u20135 cm, provided that an appropriate prediction strategy is applied and high-quality GNSS products are used. For a given fitting interval, the ephemeris fitting errors are generally related to the number of ephemeris parameters and the orbital height. Compared with the prediction errors, the ephemeris fitting errors do not play a significant role in the total error budget when using 22 ephemeris parameters.<\/jats:p>","DOI":"10.3390\/rs15010133","type":"journal-article","created":{"date-parts":[[2022,12,27]],"date-time":"2022-12-27T02:53:11Z","timestamp":1672109591000},"page":"133","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":32,"title":["Real-Time LEO Satellite Orbits Based on Batch Least-Squares Orbit Determination with Short-Term Orbit Prediction"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-5688-6937","authenticated-orcid":false,"given":"Kan","family":"Wang","sequence":"first","affiliation":[{"name":"National Time Service Center, Chinese Academy of Sciences, Xi\u2019an 710600, China"},{"name":"University of Chinese Academy of Sciences, Beijing 100049, China"}]},{"given":"Jiawei","family":"Liu","sequence":"additional","affiliation":[{"name":"National Time Service Center, Chinese Academy of Sciences, Xi\u2019an 710600, China"},{"name":"University of Chinese Academy of Sciences, Beijing 100049, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3975-9658","authenticated-orcid":false,"given":"Hang","family":"Su","sequence":"additional","affiliation":[{"name":"National Time Service Center, Chinese Academy of Sciences, Xi\u2019an 710600, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7060-4123","authenticated-orcid":false,"given":"Ahmed","family":"El-Mowafy","sequence":"additional","affiliation":[{"name":"School of Earth and Planetary Sciences, Curtin University, Perth, WA 6845, Australia"}]},{"given":"Xuhai","family":"Yang","sequence":"additional","affiliation":[{"name":"National Time Service Center, Chinese Academy of Sciences, Xi\u2019an 710600, China"},{"name":"University of Chinese Academy of Sciences, Beijing 100049, China"}]}],"member":"1968","published-online":{"date-parts":[[2022,12,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"205","DOI":"10.1002\/navi.234","article-title":"Broadband LEO constellations for navigation","volume":"65","author":"Reid","year":"2018","journal-title":"Navig. 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