Evaluation of surface clutter for the design of the TRMM spaceborne radar

Surface clutter interference through antenna sidelobes on rainfall measurements by spaceborne rain radar is quantitatively examined in order to clarify design criteria for the antenna. The received intensities of both rain echo and sea clutter are evaluated numerically, assuming appropriate precipitation and sea surface scattering models and a realistic antenna pattern for a phased array antenna, which is fed with the Taylor distribution. The results indicate that a region exists just above the sea surface where the sea surface clutter masks the backscattered power from the rain. The results also demonstrate the feasibility of quantitative measurements of rainfall in regions above this interference zone if a planar array antenna fed with the Taylor distribution of peak sidelobe level -30 dB is used