Ground-based microwave radiometry to characterize atmospheric attenuation affecting Earth-space links

This contribution provides an overview on ground-based microwave radiometric techniques to characterize atmospheric attenuation affecting Earth-space links up to millimeter wave frequencies. The classical and well-established radiometric approach is described together with its limitations of applicability to rain-free conditions. The most recent Sun-tracking approach and its capability of estimating atmospheric attenuation in all-weather conditions, developed to overcome the shortcoming of classical radiometers, is then described. Latest enhancements of Sun-tracking techniques in the estimation of the Sun brightness temperature are illustrated, along with a preview of future developments.