Extensive non-coherent averaging in Doppler beam sharpened space-borne radar altimeters

Doppler beam sharpened (DBS) radar altimeters use synthetic aperture techniques to improve the spatial resolution in the along track direction beyond the diameter of the pulse limited zone, yielding an instrument which overcomes most of the typical shortcomings that affect conventional satellite altimeters when facing surfaces more irregular than open oceans. In this paper the authors derive a generalized analytic model of the two dimensional (range/doppler) flat surface response of a DBS altimeter. The knowledge of such a function can be of great importance to derive unbiased estimators of the surface elevation at each along track position, capable to extending the multilook averaging over the whole time during which a surface element is illuminated by the antenna beam.