Field Intercomparison of Radiometers Used for Satellite Validation in the 400–900 nm Range

dc.contributor.authorVabson, Viktor
dc.contributor.authorKuusk, Joel
dc.contributor.authorAnsko, Ilmar
dc.contributor.authorVendt, Riho
dc.contributor.authorAlikas, Krista
dc.contributor.authorRuddick, Kevin
dc.contributor.authorAnsper, Ave
dc.contributor.authorBresciani, Mariano
dc.contributor.authorBurmester, Henning
dc.contributor.authorCosta, Maycira
dc.contributor.authorD’Alimonte, Davide
dc.contributor.authorDall’Olmo, Giorgio
dc.contributor.authorDamiri, Bahaiddin
dc.contributor.authorDinter, Tilman
dc.contributor.authorGiardino, Claudia
dc.contributor.authorKangro, Kersti
dc.contributor.authorLigi, Martin
dc.contributor.authorPaavel, Birgot
dc.contributor.authorTilstone, Gavin
dc.contributor.authorVan Dommelen, Ronnie
dc.contributor.authorWiegmann, Sonja
dc.contributor.authorBracher, Astrid
dc.contributor.authorDonlon, Craig
dc.contributor.authorCasal, Tânia
dc.date.accessioned2020-01-04T18:49:25Z
dc.date.available2020-01-04T18:49:25Z
dc.date.copyright2019en_US
dc.date.issued2019
dc.description.abstractAn intercomparison of radiance and irradiance ocean color radiometers (the second laboratory comparison exercise—LCE-2) was organized within the frame of the European Space Agency funded project Fiducial Reference Measurements for Satellite Ocean Color (FRM4SOC) May 8–13, 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° 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.en_US
dc.description.reviewstatusRevieweden_US
dc.description.scholarlevelFacultyen_US
dc.description.sponsorshipThis work was funded by European Spa ce Agency project Fiducial Reference Measurements for Satellite Ocean Color (FRM4SOC), contract No. 4000117454/16/I-Sbo.en_US
dc.identifier.citationVabson, V., Kuusk, J., Ansko, I., Vendt, R., Alikas, K., Ruddick, K.,… Casal, T. (2019). Field Intercomparison of Radiometers Used for Satellite Validation in the 400–900 nm Range. Remote Sensing, 11(9), 1129. https://doi.org/10.3390/rs11091129en_US
dc.identifier.urihttp://dx.doi.org/10.3390/rs11091129
dc.identifier.urihttp://hdl.handle.net/1828/11458
dc.language.isoenen_US
dc.publisherRemote Sensingen_US
dc.subjectocean color radiometersen_US
dc.subjectradiometric calibrationen_US
dc.subjectfield intercomparison measurementen_US
dc.subjectagreement between sensorsen_US
dc.subjectmeasurement uncertaintyen_US
dc.titleField Intercomparison of Radiometers Used for Satellite Validation in the 400–900 nm Rangeen_US
dc.typeArticleen_US

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