{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T00:53:36Z","timestamp":1760144016251,"version":"build-2065373602"},"reference-count":19,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2024,3,10]],"date-time":"2024-03-10T00:00:00Z","timestamp":1710028800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Beijing Nova Program","award":["Z201100006820103"],"award-info":[{"award-number":["Z201100006820103"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The L band frequency shows high sensitivity to sea surface salinity. More stable brightness temperature (TB) measurements are required for L-band radiometers to reduce salinity retrieval errors than for high-frequency radiometers. Due to the complexity of L-band synthetic aperture radiometers, a carefully selected cold-sky target should be viewed using an L-band synthetic aperture radiometer for the purpose of absolute TB calibration since the celestial sky is relatively well characterized and stable in the L band. A novel, effective cold-sky calibration strategy is presented in this paper. The strategy of cold-sky calibration of the synthetic aperture radiometer is applied when and where the antenna main lobe points to the \u2018flat\u2019 celestial sky, and the impact of each type of foreign source, such as the sun or moon, on visibility values should be minimized in the meantime. Additionally, antenna thermal stability is also considered, which can cause antenna deformation, and the antenna patterns are affected. A high-precision and high-fidelity simulator is built for the cold-sky calibration optimized strategy. The orbital beta angle is introduced to characterize the variation in space environment temperatures. A planet that is considered spherical in shape requires significantly less computation than an ellipsoid one in the simulator. The trade-off study results for the planet shape assumption in the cold-sky calibration simulator are presented. Finally, the calibration uncertainty and performance are assessed.<\/jats:p>","DOI":"10.3390\/rs16060971","type":"journal-article","created":{"date-parts":[[2024,3,11]],"date-time":"2024-03-11T08:56:41Z","timestamp":1710147401000},"page":"971","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["An Effective Onboard Cold-Sky Calibration Strategy for Spaceborne L-Band Synthetic Aperture Radiometers"],"prefix":"10.3390","volume":"16","author":[{"given":"Jingjing","family":"Ren","sequence":"first","affiliation":[{"name":"Institute of Remote Sensing Satellite, CAST, Beijing 100094, China"}]},{"given":"Huan","family":"Zhang","sequence":"additional","affiliation":[{"name":"Institute of Remote Sensing Satellite, CAST, Beijing 100094, China"},{"name":"Advanced Space Technology Laboratory, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China"}]},{"given":"Zhongkai","family":"Wen","sequence":"additional","affiliation":[{"name":"Institute of Remote Sensing Satellite, CAST, Beijing 100094, China"}]},{"ORCID":"https:\/\/orcid.org\/0009-0003-9109-0303","authenticated-orcid":false,"given":"Yan","family":"Li","sequence":"additional","affiliation":[{"name":"Faculty of Information Science and Engineering, College of Marine Technology, Ocean University of China, Qingdao 266100, China"}]},{"given":"Qingjun","family":"Zhang","sequence":"additional","affiliation":[{"name":"Institute of Remote Sensing Satellite, CAST, Beijing 100094, China"}]}],"member":"1968","published-online":{"date-parts":[[2024,3,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"646","DOI":"10.1109\/TGRS.2007.914810","article-title":"SMOS Calibration","volume":"46","author":"Brown","year":"2008","journal-title":"IEEE Trans. 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Version"}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/16\/6\/971\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T14:11:35Z","timestamp":1760105495000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/16\/6\/971"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,3,10]]},"references-count":19,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2024,3]]}},"alternative-id":["rs16060971"],"URL":"https:\/\/doi.org\/10.3390\/rs16060971","relation":{},"ISSN":["2072-4292"],"issn-type":[{"type":"electronic","value":"2072-4292"}],"subject":[],"published":{"date-parts":[[2024,3,10]]}}}