Reduction of Secondary Lobes in Aperture Synthesis Radiometry

In a synthetic aperture radiometer, the sidelobe level is determined by the shape of the synthetic pattern, which, in turn, depends on the window used to weight the visibility samples. Reduced sidelobes are obtained when the weighted visibility is smooth with no abrupt changes in the entire spatial frequency domain. Since standard 2-D windows have circular symmetry, the sidelobes are reduced if visibility samples are chosen only within a circle. This technique has been successfully tested with Soil Moisture and Ocean Salinity data, demonstrating an important reduction of sidelobes with some degradation of spatial resolution.