Radiometric Performance of the CERES Earth Radiation Budget Climate Record Sensors on the EOS Aqua and Terra Spacecraft through April 2007

Abstract

The Clouds and the Earth?s Radiant Energy System (CERES) flight models 1 through 4 instruments were launched aboard NASA?s Earth Observing System (EOS) Terra and Aqua spacecraft into 705-km sun-synchronous orbits with 10:30 p.m. and 1:30 a.m. local time equatorial crossing times. With these instruments CERES provides state-of-the-art observations and products related to the earth?s radiation budget at the top of the atmosphere (TOA). The archived CERES science data products consist of geolocated and calibrated instantaneous filtered and unfiltered radiances through temporally and spatially averaged TOA, surface, and atmospheric fluxes. CERES-filtered radiance measurements cover three spectral bands: shortwave (0.3?5 ?m), total (0.3>100 ?m), and an atmospheric window channel (8?12 ?m). CERES climate data products realize a factor of 2?4 improvement in calibration accuracy and stability over the previotus Earth Radiation Budget Experiment (ERBE) products. To achieve this improvement there are three editions of data products. Edition 1 generates data products using gain coefficients derived from ground calibrations. After a minimum of four months, the calibration data are examined to remove drifts in the calibration. The data are then reprocessed to produce the edition 2 data products. These products are available for science investigations for which an accuracy of 2% is sufficient. Also, a validation protocol is applied to these products to find problems and develop solutions, after which edition 3 data products will be computed, for which the objectives are calibration stability of better than 0.2% and calibration traceability from ground to flight of 0.25%. This paper reports the status of the radiometric accuracy and stability of the CERES edition 2 instrument data products through April 2007.