A rigorous and comprehensive radiometric calibration and validation protocol comprising of various studies was developed to evaluate the calibration accuracy of the CERES instruments. The in-flight calibration of CERES sensors are carried out using the internal calibration module (ICM) comprising of blackbody sources and quartzhalogen tungsten lamp, and a solar diffuser plate known as the Mirror Attenuator Mosaic (MAM). The ICM calibration results are instrumental in determining the changes in CERES sensors’ gains after launch from the prelaunch determined values and the on-orbit gain variations. In addition to the broadband response changes derived from the on-board blackbody and the tungsten lamp, the shortwave and the total sensors show a spectrally dependent drop in responsivity in the shorter wavelegth region below one micron that were brought to light through validation studies. The spectrally dependent changes were attributed to the instrument operational modes and the corrections were derived using the sensor radiance comparisons. This paper covers the on-orbit behavior of CERES sensors aboard the Terra and Aqua spacecraft and the determination of the sensor response changes utilising the in-flight calibration and the radiance measurement comparisons viewing various targets. The corrections for the sensor response changes were incorporated in the radiance calculations of CERES Edition3 data products.
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Susan Thomas, K. J. Priestley, M. Shankar, N. M. Smith, N. G. Loeb, D. R. Walikainen, P. C. Hess, R. S. Wilson, N. P. Smith, "Performance assessment of the Clouds and the Earth's Radiant Energy System (CERES) instruments aboard Terra and Aqua spacecraft," Proc. SPIE 8866, Earth Observing Systems XVIII, 886606 (23 September 2013);