On the Amount of Information Content in Microwave Radiometry for Wet Delay Estimation

This paper aims at determining the set of optimum frequencies to be used in the companion microwave radiometers in future synthetic aperture radar altimeters, to provide higher spatial resolution of the atmospheric water-vapor state, so as to improve the wet delay correction in the coastal regions. The channel selection is based on the study of the frequencies that provide the largest amount of information, as defined by the largest information entropy change from a prior knowledge state. It is found that four frequencies, one close to the 22-GHz peak and three other ones around 175.188 GHz, provide a near optimum compromise between the amount of information measured, and the instrument's complexity.