Cryogenically cooled transfer active cavity radiometer (TACR) for radiometric characterizations of the clouds and the Earth's radiant energy system (CERES) scanning thermistor bolometers

摘要

Abstract: A new shortwave calibration standard known as transfer active cavity radiometer (TACR) was developed by TRW to overcome the problem of nonuniform wall temperatures of the integrating sphere in ground calibration of the Earth Radiation Budget Experiment (ERBE) scanning sensors. The TACR is cryogenically cooled near 5 K, and is calibrated using the Narrow Field-of-view blackbody source at different temperatures. The TACR is used to transfer the blackbody radiometric scale of International Temperature Scale of 1990 to the shortwave calibration standard called the shortwave reference source (SWRS). The SWRS is used as the primary source for calibrating spacecraft shortwave thermistor bolometers and the shortwave portion of the total thermistor bolometers. This paper describes the TACR's design and its uses in calibrating the CERES shortwave and total bolometers in the shortwave spectral region between 0.4 to 2.0 $mu@m. On November 27, 1997, the CERES Proto-flight model instrument was launched aboard the Tropical Rainfall Measuring Mission spacecraft. During December 1998, the CERES flight models 1 and 2 will be launched aboard the EOS AM spacecraft. The resulting gain values for shortwave and total scanning sensors obtained by using the SWRS ground calibration data are detailed and discussed. !20