The Microwave Sounding Unit (MSU) scans the atmospheric column in four channels in the region of 50-60 GHz. The sensor provides daily observations of lower troposphere temperature (LTT), upper troposphere temperature (UTT), lower stratosphere temperature (LST) and oceanic precipitation (OP). The limb corrections have been applied to the off-nadir observations. 

MSU has been flown on a number of National Oceanic and Atmospheric Administration (NOAA) Polar Operational Environmental Satellites (POES) since 1979.