An Advanced HRWS Image Processing Method for MEO SAR

In this article, an advanced high-resolution wide-swath (HRWS) imaging method is presented for medium Earth orbit (MEO) synthetic aperture radar (SAR). Due to the curved satellite orbit, large squint angle, scene elevation fluctuation, and other reasons, the echo of HRWS MEO SAR exhibits high spatial dependence. In the proposed method, a high-order perturbation function is employed first to alleviate this phenomenon in the azimuth direction, and coarse focusing for the entire scene is achieved subsequently by progressive partition correlation, which can effectively handle range energy dispersion and achieve accurate focusing with a large squint angle as much as possible. However, the residual spatial dependence, introduced by high-order variation or elevation fluctuation, may still degrade the image quality. In our processing, a refining focusing kernel in the two-dimensional time domain is adopted to further improve the image quality. Benefiting from the coarse focusing step, energy dispersion for the entire scene is minimized, so the size of refining focusing kernel can be very small, and easy to be realized in a parallel form to increase processing efficiency. As demonstrated by simulation experiments, the proposed method can achieve a resolution of 0.5 m at a 20° squint angle for a 40 km swath.