The Compact Scanning Submillimeter-wave Imaging Radiometer (CoSSIR) is an airborne, 12-channel, (183 - 874 GHz) total power imaging radiometer that was mainly developed for the measurements of ice clouds. But it can be used for estimation of water vapor profiles and snowfall rates. When first completed and flown in the CRYSTAL-FACE field campaign during July 2002, the system had 15 channels at different frequencies.