The objective of this project is to derive multiple independent and highly accurate calibration references for the satellite radiation records that form the basis of the International Satellite Cloud Climatology Project (ISCCP) data set, using techniques that have been developed as part of EOS instrument calibration activities. For imager visible channels, new reference time series will be derived from deep convective cloud targets and from images of the moon that appear on the periphery of geostationary satellite images. These will be tied together with the current clear-sky albedo monitoring and NOAA-9 absolute visible references currently employed by ISCCP. Infrared calibration differences will be evaluated by comparisons to HIRS, AIRS, and CERES data. A more direct absolute standard for the IR calibration will also be established by combined comparisons of AVHRR, HIRS, MODIS, AIRS, and CERES data. Derivation of these new visible and infrared calibration references will make it possible to reprocess the ISCCP, and consequently the NASA/GEWEX Surface Radiation Budget, data sets from 1983 to the present. This will dramatically improve the accuracy of both data sets, extending them beyond their intended purposes to join the EOS data products as part of the long-term radiative flux climate data record. The advances in cross-calibration techniques developed in this project will also provide a fundamental contribution to the Global Space-based Inter-Calibration System under development by the World Meteorological Organization and the Coordinating Group for Meteorological Satellites.
