{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,24]],"date-time":"2026-03-24T18:10:12Z","timestamp":1774375812155,"version":"3.50.1"},"reference-count":34,"publisher":"MDPI AG","issue":"16","license":[{"start":{"date-parts":[[2020,8,16]],"date-time":"2020-08-16T00:00:00Z","timestamp":1597536000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000844","name":"European Space Agency","doi-asserted-by":"publisher","award":["4000129892\/20\/NL\/FF\/ab"],"award-info":[{"award-number":["4000129892\/20\/NL\/FF\/ab"]}],"id":[{"id":"10.13039\/501100000844","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100000844","name":"European Space Agency","doi-asserted-by":"publisher","award":["4000122240\/17\/I-BG"],"award-info":[{"award-number":["4000122240\/17\/I-BG"]}],"id":[{"id":"10.13039\/501100000844","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>This work presents the latest calibration results for the Copernicus Sentinel-3A and -3B and the Jason-3 radar altimeters as determined by the Permanent Facility for Altimetry Calibration (PFAC) in west Crete, Greece. Radar altimeters are used to provide operational measurements for sea surface height, significant wave height and wind speed over oceans. To maintain Fiducial Reference Measurement (FRM) status, the stability and quality of altimetry products need to be continuously monitored throughout the operational phase of each altimeter. External and independent calibration and validation facilities provide an objective assessment of the altimeter\u2019s performance by comparing satellite observations with ground-truth and in-situ measurements and infrastructures. Three independent methods are employed in the PFAC: Range calibration using a transponder, sea-surface calibration relying upon sea-surface Cal\/Val sites, and crossover analysis. Procedures to determine FRM uncertainties for Cal\/Val results have been demonstrated for each calibration. Biases for Sentinel-3A Passes No. 14, 278 and 335, Sentinel-3B Passes No. 14, 71 and 335, as well as for Jason-3 Passes No. 18 and No. 109 are given. Diverse calibration results by various techniques, infrastructure and settings are presented. Finally, upgrades to the PFAC in support of the Copernicus Sentinel-6 \u2018Michael Freilich\u2019, due to launch in November 2020, are summarized.<\/jats:p>","DOI":"10.3390\/rs12162642","type":"journal-article","created":{"date-parts":[[2020,8,17]],"date-time":"2020-08-17T04:35:51Z","timestamp":1597638951000},"page":"2642","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":27,"title":["The ESA Permanent Facility for Altimetry Calibration: Monitoring Performance of Radar Altimeters for Sentinel-3A, Sentinel-3B and Jason-3 Using Transponder and Sea-Surface Calibrations with FRM Standards"],"prefix":"10.3390","volume":"12","author":[{"given":"Stelios","family":"Mertikas","sequence":"first","affiliation":[{"name":"Technical University of Crete, Geodesy and Geomatics Engineering Laboratory,  GR 73100 Chania, Greece"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Achilleas","family":"Tripolitsiotis","sequence":"additional","affiliation":[{"name":"Space Geomatica P.C., Xanthoudidou 10A, GR 73132 Chania, Greece"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Craig","family":"Donlon","sequence":"additional","affiliation":[{"name":"European Space Agency\/European Space Research and Technology Centre (ESA\/ESTEC), Keplerlaan 1, AZ 2201 Noordwijk, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Constantin","family":"Mavrocordatos","sequence":"additional","affiliation":[{"name":"European Space Agency\/European Space Research and Technology Centre (ESA\/ESTEC), Keplerlaan 1, AZ 2201 Noordwijk, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Pierre","family":"F\u00e9m\u00e9nias","sequence":"additional","affiliation":[{"name":"European Space Agency\/European Space Research Institute (ESA\/ESRIN), Largo Galileo Galilei, I 00044 Frascati, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Franck","family":"Borde","sequence":"additional","affiliation":[{"name":"European Space Agency\/European Space Research and Technology Centre (ESA\/ESTEC), Keplerlaan 1, AZ 2201 Noordwijk, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xenophon","family":"Frantzis","sequence":"additional","affiliation":[{"name":"Technical University of Crete, Geodesy and Geomatics Engineering Laboratory,  GR 73100 Chania, Greece"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Costas","family":"Kokolakis","sequence":"additional","affiliation":[{"name":"Space Geomatica P.C., Xanthoudidou 10A, GR 73132 Chania, Greece"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Thierry","family":"Guinle","sequence":"additional","affiliation":[{"name":"Centre National d\u2019 Etudes Spatiales (CNES), CEDEX 31401 Toulouse, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2475-2568","authenticated-orcid":false,"given":"George","family":"Vergos","sequence":"additional","affiliation":[{"name":"Aristotle University of Thessaloniki, School of Geodesy and Surveying, University Box 440, 54124 Thessaloniki, Greece"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3797-8016","authenticated-orcid":false,"given":"Ilias","family":"Tziavos","sequence":"additional","affiliation":[{"name":"Aristotle University of Thessaloniki, School of Geodesy and Surveying, University Box 440, 54124 Thessaloniki, Greece"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Robert","family":"Cullen","sequence":"additional","affiliation":[{"name":"European Space Agency\/European Space Research and Technology Centre (ESA\/ESTEC), Keplerlaan 1, AZ 2201 Noordwijk, The Netherlands"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,8,16]]},"reference":[{"key":"ref_1","unstructured":"Steele, J.H. 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