Postlaunch radiometric validation of the Clouds and the Earth's Radiant Energy System (CERES) Proto-flight Model on the Tropical Rainfall Measuring Mission (TRMM) spacecraft through 1999

Each Clouds and the Earth's Radiant Energy System (CERES) instrument contai ns three scanning thermistor bolometer radiometric channels. These channels measure broadband radiances in the shortwave (0.3-5.0 mm), total (0.3->100 mum), and water vapor window regions (8-12 mum). Ground-based radiometric calibrations of the CERES flight models were conducted by TRW Inc.'s Space and Electronics Group of Redondo Beach, California. On-orbit calibration an d vicarious validation studies have demonstrated radiometric stability, def ined as long-term repeatability when measuring a constant source, at better than 0.2% for the first 18 months of science data collection. This level e xceeds by 2.5 to 5 times the prelaunch radiometric performance goals that w ere set at the 0.5% level for terrestrial energy flows and 1.0% for solar e nergy flows by the CERES Science Team. The current effort describes the rad iometric performance of the CERES Proto-Flight Model on the Tropical Rainfa ll Measuring Mission spacecraft over the first 19 months of scientific data collection.