Potential for Absolute Ionosphere and Clock Correction in Noncooperative Bistatic SAR

A method is presented to estimate and compensate the ionospheric and clock-drift perturbations that affect bistatic synthetic aperture radar (SAR) images acquired under a quasi-monostatic acquisition geometry. This is accomplished through multisquint-based processing of the interferometric phase, which allows separating the ionospheric component from the rest of the phase perturbations by processing small azimuth subapertures. It is demonstrated how the absolute, i.e., nondifferential, ionospheric phase can be estimated by exploiting the baseline of the acquisition geometry, which further allows an individual correction of each image of the bistatic pair. A mathematical model of the bistatic SAR phase perturbations, as well as an algorithm for performing their estimation and compensation, is presented. The performance of the method is assessed with end-to-end simulations of bistatic acquisitions over synthetic distributed targets.