Calibration of the meteosat-5/-6 VIS channels with help of modelled radiances

The solar channel of the geostationary meteorological satellite METEOSAT-5 is calibrated with radiance simulations of a radiative transfer model. The method compares counts from the radiometer with calculated radiances for cloud free ocean and desert, respectively. The calibration based on the model compares within 10% with the absolute calibration obtained through an aircraft campaign (Kriebel et al., 1996). A theoretical analysis gives an estimated calibration error of about 10%. The method has also been applied to calibrate the VIS channel of Meteosat-6, for which no aircraft calibration campaign has been conducted yet. In future the operational application of the method is planned during the commissioning of new satellites.