Strategies for validation of CERES instruments aboard the NPP and TERRA/AQUA satellites

The main focus of this paper is a comparison of unfiltered radiances measured by CERES instruments operating on three different platforms, namely the NPP, Terra and Aqua satellites. Data for the comparison have been continuously collected since FM5 aboard the NPP started its science mission in February of 2012. Several strategies have been devised for the purpose of comparing CERES scanners. Using a special scanning mode, viewing geometries of instruments (FM5 and FM3, and also FM5 and FM1) can be matched to enable comparison at the unfiltered radiance level, and to provide a large data set for comparing all three channels. In addition, using a special elevation scan profile on FM5 and FM3, an unprecedented high precision dataset can be collected for a more stringent test of the consistency between the two instruments. Statistics are computed for different scene types and a confidence test is applied to gridded averages to show the existing consistency between measurements taken from the two different platforms. Results of the unfiltered radiance comparison are based on ES8 or ERBE-like data product; a baseline edition for FM5, and Edition3 for FM1 and FM3.