End-to-end spectral characterization of the Clouds and the Earth's Radiant Energy System (CERES) thermistor bolometer radiometers

Fourier Transform Spectrometer (FTS) techniques are being used to characterize the spectral performance of the Clouds and the Earth's Radiant Energy System (CERES) Flight Models. Each Flight Model contains three scanning thermistor bolometer radiometric channels. These channels measure the broadband filtered radiances in the shortwave (0.3 - 5.0 micron), total (0.3 - greater than 100 micron) and 8 - 12 micron water vapor window regions. Accurate characterization of the end-to-end spectral performance is necessary to both determine the filtered radiances from standard sources during radiometric calibration, and to unfilter on-orbit radiance measurements. In order to meet the high calibration requirements deemed necessary by the CERES Science Team, a new technique which measures the broad-band end-to-end spectral response of the CERES sensors with high relative accuracy was necessary.