Ultimate determination of ScaRaB flight model 2 channel gains

The Scanner for Radiation Budget (ScaRaB) instruments are a series of Earth Radiation Budget (ERB) radiometers of which the first Right model (FM1) wa s launched on a Russian METEOR satellite in 1993. A second model (FM2) was launched on the Russian RESURS satellite in July 1998. The FM2 instrument w orked perfectly until the failure of the platform transmitter in April 1999 . Considering both missions, ERB data were obtained over sixteen months wit h ScaRaB. Tn order to obtain a good correlation between calibrations on the ground and in space in the long-wave spectral domain, the spectral respons e has been re-estimated using an original method. As the solar ground calib ration and the integrating-sphere calibration are conducted in an enclosure purged with dry nitrogen, the detector gain differs from the gain under va cuum, and a correction factor must be applied. A new correction coefficient has been determined through analysis of the ScaRaB data sets, leading to s atisfactory agreement between long-wave vacuum calibration and solar calibr ation.