Designing a Mouse-Antenna Sun-Tracking Radiometer at 89 GHZ for Atmospheric Emission and Extinction Monitoring.

The design of a millimeter-wave Mouse-Antenna Sun-Tracking radiometer at W band (MASTRad89), capable of measuring both the downwelling emitted atmospheric brightness temperature and the associated extinction over an estimated dynamic range greater than 30 dB, is discussed. The MASTRad89 instrument at W band operates with two equal antennas having the same beam width and an offset from each other by an angle of about 10 degrees (named "mouse antenna" system). A dedicated efficient solar tracking system allows to follow the apparent movement of the Sun by means a programmed controller. The two narrow-beam antennas share the same radiofrequency superheterodyne front-end chain to carry out simultaneous measurements at W band of both Sun and out-of-the-Sun atmospheric brightness temperature. Using a post-processing software, MASTRad89 can provide the atmospheric path attenuation at W band in any weather conditions, overcoming the saturation problem due to rain which is typical of conventional microwave radiometers.