Millimeter radiometric sensing of the lower atmosphere

It is pointed out that the advent of the Dicke radiometer permitted the opening of the microwave spectrum to many practical and scientific uses in the remote sensing of the lower terrestrial atmosphere. Scientific and operational sounding of the lower atmosphere by passive microwave techniques on both local and global scales was made possible. Strong microwave spectral features of oxygen and water vapor permit ground- and space-based sensors to determine the altitude profiles of atmospheic temperature and humidity with an accuracy not obtainable by comparable infrared sensors. Clouds and precipitation, as well as numerous stratospheric and mesospheric constituents, can also be measured. The origins and history of the field are reviewed.<>