<title>Radiometric calibration plan for the Clouds and the Earth's Radiant Energy System scanning instruments</title>

Abstract

The Cloud and the Earth's Radiant Energy System (CERES) program continues the long term monitoring of the Earth's energy budget begun by the Earth Radiation Budget Experiment (ERBE) scanning radiometer instruments. The radiometic ground calibration sources employed for ERBE were designed to cover the very large (all Earth) field of view of the non-scanning radiometers. The ERBE radiometer ground and flight calibration proved to be more accurate than the requirement. The ground calibration sources to be used for CERES will be optimally designed to calibrate the much more narrow field of view of the scanning radiometer to improve on the absolute calibration performance. In addition, the shortwave calibration will be made in narrow bands to eliminate uncertainty in the spectral shape of the shortwave calibration source. Each shortwave band will be absolutely calibrated by transfer to a blackbody using a cryogenic active cavity radiometer fitted with the same telescope optics as the CERES radiometers.