Pre launch studies include radiometric calibration using traceable primary standards and FTS spectral characterization techniques. Post launch efforts include data collected while viewing on-board calibration equipment such as internal blackbodies and Tungsten lamps as well as vicarious validation and intercomparison studies utilizing well characterized earth targets which are viewed simultaneously by different spectral channels and flight instruments. Each study provides unique insight to the instrumentís performance from several different perspectives. Once this ensemble of individual perspectives is collected and organized a cohesive and highly rigorous picture of the overall end-to-end performance of the CERES instrumentís and data processing algorithms may be clearly established.
An inherent requirement of this protocol is a thorough understanding of the subtle relationship between an instruments physical behavior and the scientific algorithms which convert the sensors response to higher level data products. This approach has resulted in unprecedented levels of accuracy for radiation budget instruments and data products: Calibration stability of better than 0.2%; calibration consistency from ground to space of 0.25%.
The current effort focuses on the results of this validation protocol when applied to the first 2 years of science data collected by the CERES Flight Models 1 and 2 aboard NASAís Terra Spacecraft.