Bistatic ISAR distortion mitigation of a space target via exploiting the orbital prior information

The linear-geometry distortion and image defocus are induced by the time-varying bistatic angle in a bistatic inverse synthetic aperture radar (Bi-ISAR) system. Here, a distortion mitigation algorithm of a space target is proposed via exploiting the orbital prior information. First, the linear/quadratic distortions are analysed in the Range-Doppler (RD) image formation mathematics. The coefficients of the time-varying bistatic angle are estimated by means of the orbit information of the target and the imaging geometry. Second, the equivalent rotation centre (RC) is estimated iteratively based on the maximum image contrast criterion. Third, the linear-geometry distortion and quadratic distortion related with the range position are restored by the compensation of the spatial-varying phase terms. Finally, the well-focused image is achieved by applying the matching Fourier transform (MFT) along the cross-range direction. Experimental results based on both the ideal point scatterers model and numerical electromagnetic (EM) data are provided to support the algorithm.