{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,19]],"date-time":"2026-01-19T01:46:55Z","timestamp":1768787215080,"version":"3.49.0"},"reference-count":39,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2020,9,18]],"date-time":"2020-09-18T00:00:00Z","timestamp":1600387200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The Sentinel-3A and Sentinel-3B satellites were launched, respectively, on 16 February 2016 and 25 April 2018 as part of the European Copernicus program. The Sentinel-3 Surface Topography Mission makes use of the altimeter instruments onboard Sentinel-3A and Sentinel-3B to provide elevation measurements not only of the ocean water level but also of the inland waters and ice caps. For the first time, the altimeters onboard Sentinel-3A and Sentinel-3B are operated in Synthetic Aperture Radar mode over all Earth surfaces. They also benefit from elevation priors (the Open-Loop Tracking Command) allowing them to precisely position their receiving window to track the backscattered signal from the inland water targets to be monitored rather than relying on the traditional Closed-Loop tracking mode. This paper makes use of the Sentinel-3A\/Sentinel-3B tandem phase to assess the benefits of the Open-Loop tracking mode compared to Closed-Loop. Longer time series are also used to highlight the improvements in terms of the percentage of points over which the altimeter hooks on water surfaces and water surface height estimation brought by the switch of Sentinel-3A from the Closed-Loop to Open-Loop tracking mode as well as the successive Open-Loop Tracking Command updates. In particular, it is shown that from a Level-3 water level product service perspective, the increase in the number of water bodies with valid water surface height estimates is of the order of 25% in Open-Loop with respect to Closed-Loop with similar precision. It is also emphasized that the Open-Loop Tracking Command update onboard Sentinel-3A from v. 4.2 to v. 5.0 yielded a 30% increase in the number of water bodies over which valid water surface height could be estimated. Eventually, the importance of knowing whether a water target was associated with a fine-tuned Open-Loop Tracking Command or an interpolated one is stressed and the recommendation to provide such a flag in the Sentinel-3 Level2 Payload Data Ground Segment products is emitted.<\/jats:p>","DOI":"10.3390\/rs12183055","type":"journal-article","created":{"date-parts":[[2020,9,18]],"date-time":"2020-09-18T10:22:23Z","timestamp":1600424543000},"page":"3055","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":29,"title":["S3MPC: Improvement on Inland Water Tracking and Water Level Monitoring from the OLTC Onboard Sentinel-3 Altimeters"],"prefix":"10.3390","volume":"12","author":[{"given":"Nicolas","family":"Taburet","sequence":"first","affiliation":[{"name":"CLS, Parc Technologique du Canal, 11 Rue Herm\u00e8s, 31520 Ramonville Saint-Agne, France"}]},{"given":"Lionel","family":"Zawadzki","sequence":"additional","affiliation":[{"name":"CLS, Parc Technologique du Canal, 11 Rue Herm\u00e8s, 31520 Ramonville Saint-Agne, France"},{"name":"CNES, 18 Avenue Edouard Belin, CEDEX 31401 Toulouse, France"}]},{"given":"Maxime","family":"Vayre","sequence":"additional","affiliation":[{"name":"CLS, Parc Technologique du Canal, 11 Rue Herm\u00e8s, 31520 Ramonville Saint-Agne, France"}]},{"given":"Denis","family":"Blumstein","sequence":"additional","affiliation":[{"name":"CNES, 18 Avenue Edouard Belin, CEDEX 31401 Toulouse, France"},{"name":"LEGOS, 14 Avenue Edouard Belin, 31400 Toulouse, France"}]},{"given":"Sophie","family":"Le Gac","sequence":"additional","affiliation":[{"name":"CNES, 18 Avenue Edouard Belin, CEDEX 31401 Toulouse, France"}]},{"given":"Fran\u00e7ois","family":"Boy","sequence":"additional","affiliation":[{"name":"CNES, 18 Avenue Edouard Belin, CEDEX 31401 Toulouse, France"}]},{"given":"Matthias","family":"Raynal","sequence":"additional","affiliation":[{"name":"CLS, Parc Technologique du Canal, 11 Rue Herm\u00e8s, 31520 Ramonville Saint-Agne, France"}]},{"given":"Sylvie","family":"Labroue","sequence":"additional","affiliation":[{"name":"CLS, Parc Technologique du Canal, 11 Rue Herm\u00e8s, 31520 Ramonville Saint-Agne, France"}]},{"given":"Jean-Fran\u00e7ois","family":"Cr\u00e9taux","sequence":"additional","affiliation":[{"name":"CNES, 18 Avenue Edouard Belin, CEDEX 31401 Toulouse, France"},{"name":"LEGOS, 14 Avenue Edouard Belin, 31400 Toulouse, France"}]},{"given":"Pierre","family":"Femenias","sequence":"additional","affiliation":[{"name":"ESA-ESRIN, Largo Galileo Galilei, 1, 00044 Frascati RM, Italy"}]}],"member":"1968","published-online":{"date-parts":[[2020,9,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"247","DOI":"10.1007\/s10712-008-9051-1","article-title":"Monitoring Continental Surface Waters by Satellite Altimetry","volume":"29","author":"Calmant","year":"2008","journal-title":"Surv. Geophys."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Alsdorf, D.E., Rodr\u00edguez, E., and Lettenmaier, D.P. (2007). Measuring surface water from space. Rev. Geophys., 45.","DOI":"10.1029\/2006RG000197"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1098","DOI":"10.1016\/j.crte.2006.08.002","article-title":"Lake studies from satellite radar altimetry","volume":"338","author":"Birkett","year":"2006","journal-title":"Comptes Rendus Geosci."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"78","DOI":"10.1016\/j.jhydrol.2013.09.010","article-title":"Evaluation of multiple satellite altimetry data for studying inland water bodies and river floods","volume":"505","author":"Jarihani","year":"2013","journal-title":"J. Hydrol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"269","DOI":"10.1029\/2003EO290001","article-title":"The need for global, satellite-based observations of terrestrial surface waters","volume":"84","author":"Alsdorf","year":"2003","journal-title":"Eos Trans. Am. Geophys. Union"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1497","DOI":"10.1016\/j.asr.2011.01.004","article-title":"SOLS, a lake database to monitor in Near real time water level storage variations from remote sensing data","volume":"47","author":"Cretaux","year":"2011","journal-title":"Adv. Space Res."},{"key":"ref_7","unstructured":"Birkett, C.M., Ricko, M., Beckley, B.D., Yang, X., and Tetrault, R.L. (2017). G-REALM: A lake\/reservoir monitoring tool for drought monitoring and water resources management. AGU Fall Meeting Abstracts, American Geophysical Union. AGUFM, H23P-02."},{"key":"ref_8","unstructured":"Schwatke, C., and Dettmering, D. (2017, January 19\u201321). DAHITI: Inland Water Levels from Space for Climate Studies. Proceedings of the IAG Workshop: Satellite Geodesy for Climate Studies, Bonn, Germany."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1030","DOI":"10.1016\/j.asr.2011.11.018","article-title":"First quality assessment of the Cryosat-2 altimetric system over ocean","volume":"50","author":"Labroue","year":"2012","journal-title":"Adv. Space Res."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"148","DOI":"10.1109\/TGRS.2016.2601958","article-title":"CryoSat-2 SAR-mode over oceans: Processing methods, global assessment, and benefits","volume":"55","author":"Boy","year":"2016","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"121","DOI":"10.5194\/tc-10-121-2016","article-title":"Utilisation of CryoSat-2 SAR altimeter in operational ice charting","volume":"10","author":"Rinne","year":"2016","journal-title":"Cryosphere"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1539","DOI":"10.5194\/tc-8-1539-2014","article-title":"Elevation and elevation change of Greenland and Antarctica derived from CryoSat-2","volume":"8","author":"Helm","year":"2014","journal-title":"Cryosphere"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"234","DOI":"10.1016\/j.jhydrol.2016.03.051","article-title":"Improved inland water levels from SAR altimetry using novel empirical and physical retrackers","volume":"537","author":"Villadsen","year":"2016","journal-title":"J. Hydrol."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"162","DOI":"10.1016\/j.rse.2015.10.023","article-title":"Validation of CryoSat-2 SAR mode based lake levels","volume":"171","author":"Nielsen","year":"2015","journal-title":"Remote Sens. Environ."},{"key":"ref_15","unstructured":"Le Gac, S., Boy, F., Blumstein, D., Lasson, L., and Picot, N. (2019). Benefits of the Open-Loop Tracking Command (OLTC): Extending conventional nadir altimetry to inland waters monitoring. Adv. Space Res."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2277","DOI":"10.1175\/JTECH-D-16-0011.1","article-title":"Evaluating the Performance of Jason-2 Open-Loop and Closed-Loop Tracker Modes","volume":"33","author":"Leuliette","year":"2016","journal-title":"J. Atmos. Oceanic Technol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"77","DOI":"10.1016\/j.rse.2018.02.037","article-title":"Validation of Jason-3 tracking modes over French rivers","volume":"209","author":"Biancamaria","year":"2018","journal-title":"Remote Sens. Environ."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"111546","DOI":"10.1016\/j.rse.2019.111546","article-title":"Evaluation of Sentinel-3 SRAL SAR altimetry over Chinese rivers","volume":"237","author":"Jiang","year":"2020","journal-title":"Remote Sens. Environ."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"e2020GL088770","DOI":"10.1029\/2020GL088770","article-title":"On the performance of Sentinel-3 altimetry over new reservoirs: Approaches to determine onboard a priori elevation","volume":"47","author":"Zhang","year":"2020","journal-title":"Geophys. Res. Lett."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Frappart, F., Blarel, F., Papa, F., Prigent, C., Mougin, E., Paillou, P., Baup, F., Zeiger, P., Salameh, E., and Darrozes, J. (2020). Backscattering signatures at Ka, Ku, C and S bands from low resolution radaraltimetry over land. Adv. Space Res.","DOI":"10.1016\/j.asr.2020.06.043"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Kittel, C.M.M., Jiang, L., T\u00f8ttrup, C., and Bauer-Gottwein, P. (2020). Sentinel-3 radar altimetry for river monitoring\u2014A catchment-scale evaluation of satellite water surface elevation from Sentinel-3A and Sentinel-3B. Hydrol. Earth Syst. Sci. Discuss.","DOI":"10.5194\/hess-2020-165"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"2181","DOI":"10.5194\/hess-16-2181-2012","article-title":"River monitoring from satellite radar altimetry in the Zambezi River basin","volume":"16","author":"Michailovsky","year":"2012","journal-title":"Hydrol. Earth Syst. Sci."},{"key":"ref_23","unstructured":"ESA (2020, July 31). Sentinel Online-Overview. Available online: https:\/\/sentinel.esa.int\/web\/sentinel\/missions\/sentinel-3\/satellite-description\/orbit."},{"key":"ref_24","unstructured":"ESA (2020, July 31). Sentinel Online-Overview-Altimetry Principles. Available online: https:\/\/sentinel.esa.int\/web\/sentinel\/user-guides\/sentinel-3-altimetry\/overview\/altimetry-principles."},{"key":"ref_25","unstructured":"(2020, July 31). Aviso Website. Available online: https:\/\/www.aviso.altimetry.fr\/techniques\/altimetry\/principle.html."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Dinardo, S., Lucas, B., and Benveniste, J. (2015, January 26\u201331). Sentinel-3 STM SAR ocean retracking algorithm and SAMOSA model. Proceedings of the 2015 IEEE International Geoscience and Remote Sensing Symposium (IGARSS), Milan, Italy.","DOI":"10.1109\/IGARSS.2015.7327036"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Quartly, G.D., Nencioli, F., Raynal, M., and Bonnefond, P. (2020). The Roles of the S3MPC: Monitoring, Validation and Evolution of Sentinel-3 altimetry observations. Remote Sens., 12.","DOI":"10.3390\/rs12111763"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1080\/01490419.2010.488970","article-title":"POSEIDON-3 Radar Altimeter New Modes and In-Flight Performances","volume":"33","author":"Desjonqueres","year":"2010","journal-title":"Mar. Geod."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"409","DOI":"10.1002\/2013EO450001","article-title":"Generic Mapping Tools: Improved Version Released","volume":"94","author":"Wessel","year":"2013","journal-title":"EOS Trans. AGU"},{"key":"ref_30","unstructured":"Bicheron, P., Leroy, M., Nino, F., Defourny, P., Vancutsem, C., Brockman, C., Kr\u00e4mer, U., Berthelot, B., Miras, B., and Huc, M. (2006, January 25\u201329). Globcover: A 300 m res. Global land cover product using MERIS time series over 2005\/2006. Proceedings of the 2nd International Symposium on Recent Advances in Quantitative Remote Sensing, Valencia, Spain."},{"key":"ref_31","unstructured":"Smith, R.G., and Berry, P.A.M. (2008, January 23\u201327). Representation of rivers and Lakes within the forthcoming ACE2 GDEM. Proceedings of the IAG International Symposium on Gravity, Geoid & Earth Observation 2008, Crete, Greece."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.jhydrol.2004.03.028","article-title":"Development and validation of a global database of lakes, reservoirs and wetlands","volume":"296","author":"Lehner","year":"2004","journal-title":"J. Hydrol."},{"key":"ref_33","unstructured":"SWDB (2020, July 31). Shuttle Radar Topography Mission Water Body Data, Available online: https:\/\/catalog.data.gov\/dataset\/nasa-shuttle-radar-topography-mission-water-body-data-shapefiles-raster-files-v003."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"418","DOI":"10.1038\/nature20584","article-title":"High-resolution mapping of global surface water and its long-term changes","volume":"540","author":"Pekel","year":"2016","journal-title":"Nature"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"494","DOI":"10.1890\/100125","article-title":"High-resolution mapping of the world\u2019s reservoirs and dams for sustainable river-flow management","volume":"9","author":"Lehner","year":"2011","journal-title":"Front. Ecol. Environ."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"13603","DOI":"10.1038\/ncomms13603","article-title":"Estimating the volume and age of water stored in global lakes using a geo-statistical approach","volume":"7","author":"Messager","year":"2016","journal-title":"Nat. Commun."},{"key":"ref_37","unstructured":"(2020, July 31). Algorithm Theoretical Basis Document of the Copernicus Global Land Water Level Product. Available online: https:\/\/land.copernicus.eu\/global\/products\/wl."},{"key":"ref_38","unstructured":"(2020, July 31). ESA. Available online: https:\/\/sentinel.esa.int\/web\/sentinel\/technical-guides\/sentinel-3-altimetry\/processing-baseline."},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Gao, Q., Makhoul, E., Escorihuela, M.J., Zribi, M., Quintana Segu\u00ed, P., Garc\u00eda, P., and Roca, M. (2019). Analysis of Retrackers\u2019 Performances and Water Level Retrieval over the Ebro River Basin Using Sentinel-3. Remote Sens., 11.","DOI":"10.3390\/rs11060718"}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/12\/18\/3055\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T10:11:19Z","timestamp":1760177479000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/12\/18\/3055"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,9,18]]},"references-count":39,"journal-issue":{"issue":"18","published-online":{"date-parts":[[2020,9]]}},"alternative-id":["rs12183055"],"URL":"https:\/\/doi.org\/10.3390\/rs12183055","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2020,9,18]]}}}