A spectral method of calculating the baselines of bistatic sar interferometers

We present a method that uses the spectral wavenumber domain to estimate the temporal lag of synthetic-aperture radar (SAR) interferometers. The method uses the surface-projected region of support of a given resolution cell of each of the two SAR images that forms the interferogram. Despite the spectral method agreeing with the conventional geometric method for the monostatic interferometer case with an along-track separation, the two methods diverge in bistatic cases of formation flying interferometers. We show that the geometric approximation overestimates the temporal lag when the two SARs fly in a close-formation or have a squinted line of sight with respect to the zero-Doppler direction.