Extended scintillation phase gradient autofocus in future spaceborne P-band SAR mission

A future spaceborne P-band synthetic aperture radar (SAR) working system will be inevitably influenced by ionospheric scintillation, which tends to cause azimuth decorrelation and azimuth-imaging degradation. The scintillation phase error (SPE) history spatially varies by 2D scenes, and this leads to the complexity of SPE estimation and compensation. In this paper, to address this problem, an approach based on the extended scintillation phase gradient autofocus (ESPGA) technique has been proposed. ESPGA is composed of three modules: local estimation, overall estimation, and correction. First, it employs the block PGA (BPGA) to estimate SPE associated with the local block. Second, by taking advantage of information redundancy of SPE estimates, azimuth splicing and range interpolation are applied to estimate the overall SPE distribution across the whole scene. Then, the estimation result corresponding to the overall SPE is considered to compensate the spatial-variant SPE and mitigate scintillation impacts on the spaceborne SAR images. Finally, a processing experiment based on a simulated image derived from an airborne P-band SAR real scene is conducted to demonstrate the effectiveness of the proposed methodology.