Performance Stability Evaluation of Clouds and the Earth'S Radiant Energy System (CERES) Flight Model S(FMS) Instrument on S-NPP

Clouds and the Earth's Radiant Energy System (CERES) Flight Model 5 (FM5) instrument is designed to continue the long-term monitoring of the Earth's radiation budget. Flight Model 5, the sixth of the CERES instrument was launched aboard the NPP spacecraft on October 2011 and it has started the Earth-viewing measurements on January 26, 2012. The CERES instrument with the three scanning sensors measure radiances in 0.3 to 5.0 micron region with Shortwave sensor, 0.3 to > 100 microns with Total sensor and 8 to 12 micron region with Window sensor. The prelaunch accuracy goal for the CERES instrument measurements is to have the emitted longwave radiances within 0.5% and the shortwave radiances within 1.0%. An accurate determination of the radiometric gains and spectral responsivity of CERES FM5 sensors was accomplished through rigorous calibrations using the primary sources. Post-launch evaluation of the sensor performance consists of sensor calibrations with the on-board sources and the solar diffuser called Mirror Attenuator Mosaic (MAM). Several validation studies utilising targets such as tropical ocean and deep convective clouds are performed as part of the CallVal protocol. This paper covers the overall performance of the CERES-FM5 instrument. The post-launch calibration and the validation results from the instrument are presented.