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Vicarious adjustment of marine reflectance for MERIS

Constant Mazeran(1), Kathryn Barker(2), Samantha Lavender(2), Ludovic Bourg(1) and David Antoine(3)

(1) ACRI-ST, 260 route du Pin Montard, 06904 Sophia Antipolis, France
(2) ARGANS Limited, Tamar Science Park, 1 Davy Road, Derriford, Plymouth, Devon, PL6 8BX, United Kingdom
(3) Laboratoire d’Oceanographie de Villefranche (LOV), Caserne Nicolas, Quai de la Darse, 06230, Villefranche sur mer, France

Abstract

A vicarious adjustment is often performed for ocean colour sensors, which accounts for changes in the radiometric calibration and errors in the atmospheric correction process. This is based on computing multiplicative gains for the top of atmosphere reflectances with a method that decouples the NIR and visible channels. An iterative procedure within the atmospheric correction algorithm is thus avoided, and allows the process to make use of an expanding database of reference in situ reflectance signals. However, this methodology makes several assumptions that introduce potential for error in the calculated gain factors and include: the near infra-red channel at 865 nm is set as a gain of 1, which assumes it’s calibrated correctly; measured in situ reflectance has no errors; angstrom exponent and diffuse transmittance can be estimated accurately. Therefore, within the context of the MERIS vicarious adjustment, a sensitivity analysis is being performed to understand the assumptions and potentially propose improvements to the methodology.

 

Workshop presentation

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry