{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,24]],"date-time":"2026-04-24T14:15:10Z","timestamp":1777040110083,"version":"3.51.4"},"reference-count":23,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2019,5,11]],"date-time":"2019-05-11T00:00:00Z","timestamp":1557532800000},"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":["4000117454\/16\/I-Sbo"],"award-info":[{"award-number":["4000117454\/16\/I-Sbo"]}],"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>An intercomparison of radiance and irradiance ocean color radiometers (the second laboratory comparison exercise\u2014LCE-2) was organized within the frame of the European Space Agency funded project Fiducial Reference Measurements for Satellite Ocean Color (FRM4SOC) May 8\u201313, 2017 at Tartu Observatory, Estonia. LCE-2 consisted of three sub-tasks: (1) SI-traceable radiometric calibration of all the participating radiance and irradiance radiometers at the Tartu Observatory just before the comparisons; (2) indoor, laboratory intercomparison using stable radiance and irradiance sources in a controlled environment; (3) outdoor, field intercomparison of natural radiation sources over a natural water surface. The aim of the experiment was to provide a link in the chain of traceability from field measurements of water reflectance to the uniform SI-traceable calibration, and after calibration to verify whether different instruments measuring the same object provide results consistent within the expected uncertainty limits. This paper describes the third phase of LCE-2: The results of the field experiment. The calibration of radiometers and laboratory comparison experiment are presented in a related paper of the same journal issue. Compared to the laboratory comparison, the field intercomparison has demonstrated substantially larger variability between freshly calibrated sensors, because the targets and environmental conditions during radiometric calibration were different, both spectrally and spatially. Major differences were found for radiance sensors measuring a sunlit water target at viewing zenith angle of 139\u00b0 because of the different fields of view. Major differences were found for irradiance sensors because of imperfect cosine response of diffusers. Variability between individual radiometers did depend significantly also on the type of the sensor and on the specific measurement target. Uniform SI traceable radiometric calibration ensuring fairly good consistency for indoor, laboratory measurements is insufficient for outdoor, field measurements, mainly due to the different angular variability of illumination. More stringent specifications and individual testing of radiometers for all relevant systematic effects (temperature, nonlinearity, spectral stray light, etc.) are needed to reduce biases between instruments and better quantify measurement uncertainties.<\/jats:p>","DOI":"10.3390\/rs11091129","type":"journal-article","created":{"date-parts":[[2019,5,13]],"date-time":"2019-05-13T05:35:39Z","timestamp":1557725739000},"page":"1129","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":29,"title":["Field Intercomparison of Radiometers Used for Satellite Validation in the 400\u2013900 nm Range"],"prefix":"10.3390","volume":"11","author":[{"given":"Viktor","family":"Vabson","sequence":"first","affiliation":[{"name":"Tartu Observatory, University of Tartu, 61602 T\u00f5ravere, Estonia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7565-1244","authenticated-orcid":false,"given":"Joel","family":"Kuusk","sequence":"additional","affiliation":[{"name":"Tartu Observatory, University of Tartu, 61602 T\u00f5ravere, Estonia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ilmar","family":"Ansko","sequence":"additional","affiliation":[{"name":"Tartu Observatory, University of Tartu, 61602 T\u00f5ravere, Estonia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3740-0772","authenticated-orcid":false,"given":"Riho","family":"Vendt","sequence":"additional","affiliation":[{"name":"Tartu Observatory, University of Tartu, 61602 T\u00f5ravere, Estonia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Krista","family":"Alikas","sequence":"additional","affiliation":[{"name":"Tartu Observatory, University of Tartu, 61602 T\u00f5ravere, 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Centre for Earth Observation, Plymouth PL1 3DH, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4671-6998","authenticated-orcid":false,"given":"Bahaiddin","family":"Damiri","sequence":"additional","affiliation":[{"name":"Cimel Electronique S.A.S, 75011 Paris, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tilman","family":"Dinter","sequence":"additional","affiliation":[{"name":"Alfred Wegener Institute Helmholtz Center for Polar and Marine Research, D-27570 Bremerhaven, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3937-4988","authenticated-orcid":false,"given":"Claudia","family":"Giardino","sequence":"additional","affiliation":[{"name":"National Research Council of Italy, 21020 Ispra, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kersti","family":"Kangro","sequence":"additional","affiliation":[{"name":"Tartu Observatory, 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