6533b823fe1ef96bd127f58d

RESEARCH PRODUCT

Vicarious calibration of MERIS over dark waters in the near infrared

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Abstract We propose to evaluate the calibration of MERIS (MEdium Resolution Imaging Spectrometer) over dark waters in the near infrared. We work with 5 months of data, from July to November 2003, over five world sites: Venice and Lampedusa in Italy, El Arenosillo in Spain, MOBY/Lanai and CalCOFI/San Nicolas in the United States. The sites are all equipped with a CIMEL station that forms part of the AERONET network. The basic idea is to associate CIMEL sky radiance measurements with MERIS level-1b data in a twin geometry which corresponds to the same scattering angle. This vicarious calibration relies on an accurate description of the atmospheric scattering based on the CIMEL measurements. After a selection of MERIS and CIMEL data we finally obtained 8 days for the calibration task—about 10% of the initial dataset. We achieved a match-up analysis at 6 MERIS wavelengths, from 884 nm to 664 nm, in the near infrared (NIR). Results show an agreement between the onboard calibration and our method within 1.5% in the NIR which falls in the expected accuracy of the two methods.