NASA - National Aeronautics and Space Administration

A desert daily exoatmospheric radiance model (DERM) based on a well-calibrated (reference) geostationary Earth orbit (GEO) satellite visible sensor can be used to transfer the calibration to a (target) GEO sensor located at the same equatorial longitude location. The DERM is based on the reference GEO daily radiances observed over a single pseudoinvariant calibration site (PICS) being that the daily angular conditions are repeated annually for any historical or successive colocated GEO. The GEO-specific PICSs used in the study are first inspected using the well-calibrated Aqua-MODerate Resolution Imaging Spectroradiometer (MODIS) exoatmospheric reflectances for stability. The Libyan Desert site was found to be stable within 1% over ten years. The average clear-sky daily local-noon interannual variability based on Meteosat-9 0.65-μm top-of-atmosphere radiances over the Libyan Desert is 0.74%, which implies that the combined surface and atmospheric column is invariant. A spectral band adjustment factor, based on Scanning Imaging Absorption Spectrometer for Atmospheric Cartography spectral radiances, is used to account for sensor spectral response function (SRF) differences between the reference and target GEO. The GEO reference calibration was based on the GEO/Aqua-MODIS ray-matched radiance intercalibration transfer technique. The reference Meteosat-9 DERM and ray-matched calibration consistency was within 0.4% and 1.9% for Meteosat-8 and Meteosat-7, respectively. Similarly, GOES-10 and GOES-15 were calibrated based on the GOES-11 DERM using the Sonoran Desert and were found to have a consistency within 1% and 3%, respectively.