<title>ScaRaB Earth radiation budget scanning radiometer</title>

A Scanning Radiometer for Radiation Balance (ScaRaB) to be flown on a series of METEOR-3 Soviet polar orbiting weather satellites is described. The radiometer comprises 2 broad channels (0.2-50 microns, 0.2-4 microns) for radiation budget, and two narrower bands (0.5-0.7 micron, 10.5-12.5 microns) for scene identification, with spatial resolution at nadir of about 50 km. The set of on-board sources includes blackbody simulators for the calibration of long-wave channels, and tungsten filament lamps and mosaic array diffusers for short wave calibration. A specific filtering scheme protects solar diffusers and lamps from the impact of thermal environment during calibration of the 0.2-50 micron channel.