Modelling Sar Scalloping in Burst Mode Products from Radarsat-1 and Envisat

RESUME A model is developed for the quantitative prediction of the azimuth radiometric modulation, commonly known as scalloping, that is occasionally present in burst mode SAR products from RADARSAT-1 and ENVISAT. The model is based on the combined effects of poor Doppler estimation, placement of the burst sequence in the azimuth beam pattern for the target area, and the details involved in performing azimuth compression of the data. The model is applied to both RADARSAT-1 and ENVISAT data and a number of general and sensor specific results emerge. General results include: the ground spacing of the scalloping pattern is equal to the beam azimuth sweep during the burst cycle period; the depth of the scallop depends generally on the size of the Doppler mismatch as well as the configuration of the processor and imaging system. Some residual scalloping is possible however even when there is no Doppler centroid error. Finally, scalloping is not an energy conservative process and the overall power in the image is changed when it is present. Specific cases are modelled for the burst modes of both RADARSAT-1 and ENVISAT where results are reviewed for traditional azimuth look weightings including unity, inverse azimuth, and Bamler.