Along-track resolution enhancement for bistatic imaging in burst-mode operation

Wide-swath synthetic aperture radar (SAR) imaging modes, such as ScanSAR or Terrain Observation by Progressive Scan SAR, share the synthetic aperture length between beam positions. This leads to a degraded along-track resolution compared to the conventional Stripmap mode.We show that this degraded resolution can be enhanced in the case of a bistatic configuration by exploiting the sidelobe emissions of the elevation beams illuminating the adjacent subswaths. If the SNR of the backscattered signals is sufficient, the performance of the Stripmap mode can even be restored. This concept becomes particularly useful when spaceborne illuminators of opportunity are considered. Indeed, the imaging mode of spaceborne SAR instruments is most often a wide-swath mode. Making it possible to exploit those modes to produce images with high azimuthal resolution dramatically increases the number of useful images that can be produced using emitters of opportunity. Signals from any radar satellite in the receiving band of the receiver can be used, thus further decreasing the revisit time of the area of interest. This paper proposes a cross-range resolution-enhancement method that provides an enhanced cross-range resolution compared to the one obtained by the classical burst-mode SAR processing. This method is experimentally validated using measurements acquired in a space-ground bistatic configuration.