Microwave and Millimeter Wave Radiometry

A microwave radiometric sensor is a device for the detection of electromagnetic energy which is noise-like in character. The spatial as well as spectral characteristics of observed energy sources determine the performance requirements imposed on the functional subsystems of the sensor. These subsystems include an antenna, receiver, and output indicator. Natural or non-man-made sources or radiation may be either spatially discrete or extended. In the frequency domain, these sources may be either broadband or of the resonant line type. Sensor design and performance characteristics are primarily determined by the extent to which spatial and frequency parameters characterize the radio noise source of interest to the observer.

A microwave radiometric sensor is frequently referred to as a temperature measuring device, since the output indicator is calibrated in degrees Kelvin. The reason why microwave radiometers are calibrated in temperature units and the modes of operation that are most frequently used are described in the white paper