{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T03:55:59Z","timestamp":1760241359178,"version":"build-2065373602"},"reference-count":44,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2018,1,5]],"date-time":"2018-01-05T00:00:00Z","timestamp":1515110400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["41604003","41704017","41574013"],"award-info":[{"award-number":["41604003","41704017","41574013"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Spaceborne GNSS-R (global navigation satellite system reflectometry) is an innovative and powerful bistatic radar remote sensing technique that uses specialized GNSS-R instruments on LEO (low Earth orbit) satellites to receive GNSS L-band signals reflected by the Earth\u2019s surface. Unlike monostatic radar, the illuminated areas are elliptical regions centered on specular reflection points. Evaluation of the spatiotemporal resolution of the reflections is necessary at the GNSS-R mission design stage for various applications. However, not all specular reflection signals can be received because the size and location of the GNSS-R antenna\u2019s available reflecting ground coverage depends on parameters including the on-board receiver antenna gain, the signal frequency and power, the antenna face direction, and the LEO\u2019s altitude. Additionally, the number of available reflections is strongly related to the number of GNSS-R LEO and GNSS satellites. By 2020, the Galileo and BeiDou Navigation Satellite System (BDS) constellations are scheduled to be fully operational at global scale and nearly 120 multi-GNSS satellites, including Global Positioning System (GPS) and Global Navigation Satellite System (GLONASS) satellites, will be available for use as illuminators. In this paper, to evaluate the future capacity for repetitive GNSS-R observations, we propose a GNSS satellite selection method and simulate the orbit of eight-satellite LEO and partial multi-GNSS constellations. We then analyze the spatiotemporal distribution characteristics of the reflections in two cases: (1) When only GPS satellites are available; (2) when multi-GNSS satellites are available separately. Simulation and analysis results show that the multi-GNSS-R system has major advantages in terms of available satellite numbers and revisit times over the GPS-R system. Additionally, the spatial density of the specular reflections on the Earth\u2019s surface is related to the LEO inclination and constellation construction.<\/jats:p>","DOI":"10.3390\/rs10010067","type":"journal-article","created":{"date-parts":[[2018,1,8]],"date-time":"2018-01-08T04:21:21Z","timestamp":1515385281000},"page":"67","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":18,"title":["Spatiotemporal Evaluation of GNSS-R Based on Future Fully Operational Global Multi-GNSS and Eight-LEO Constellations"],"prefix":"10.3390","volume":"10","author":[{"given":"Fan","family":"Gao","sequence":"first","affiliation":[{"name":"Institute of Space Science, Shandong University, Weihai 264209, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5818-6264","authenticated-orcid":false,"given":"Tianhe","family":"Xu","sequence":"additional","affiliation":[{"name":"Institute of Space Science, Shandong University, Weihai 264209, China"}]},{"given":"Nazi","family":"Wang","sequence":"additional","affiliation":[{"name":"Institute of Space Science, Shandong University, Weihai 264209, China"}]},{"given":"Chunhua","family":"Jiang","sequence":"additional","affiliation":[{"name":"Institute of Space Science, Shandong University, Weihai 264209, China"}]},{"given":"Yujun","family":"Du","sequence":"additional","affiliation":[{"name":"Institute of Space Science, Shandong University, Weihai 264209, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5505-2903","authenticated-orcid":false,"given":"Wenfeng","family":"Nie","sequence":"additional","affiliation":[{"name":"Institute of Space Science, Shandong University, Weihai 264209, China"}]},{"given":"Guochang","family":"Xu","sequence":"additional","affiliation":[{"name":"Institute of Space Science, Shandong University, Weihai 264209, China"}]}],"member":"1968","published-online":{"date-parts":[[2018,1,5]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"111","DOI":"10.1016\/j.asr.2010.01.014","article-title":"GNSS reflectometry and remote sensing: New objectives and results","volume":"46","author":"Jin","year":"2010","journal-title":"Adv. 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