The Global Energy and Water Cycle Experiment (GEWEX) Radiation Panel initiated the GEWEX Cloud Assessment in 2005 to compare available, global, long-term cloud data products with the International Satellite Cloud Climatology Project (ISCCP). The GEWEX Cloud Assessment database included cloud properties retrieved from different satellite sensor measurements, taken at various local times and over various time periods. The relevant passive satellite sensors measured radiation scattered or emitted by Earth's surface and by its atmosphere including clouds. Specific spectral domains were exploited for particular retrieval methods to maximize the sensitivity to the presence of clouds and to determine key cloud properties. ISCCP also emphasized on temporal resolution over spectral resolution to resolve the diurnal cycle of clouds the GEWEX cloud climate record.