Impact of platform motion on wide angle synthetic aperture radar (SAR) image quality

In synthetic aperture radar (SAR), the deviations of the platform motion away from a straight line degrades the achievable SAR image quality. This problem is particularly acute for foliage penetration radars (FOPEN) which need to operate in the VHF-UHF band to penetrate the foliage. Achieving high resolution in the VHF-UHF band requires long coherent integration times, over which platforms typically experience significant deviations from a straight line. Techniques exist that can produce good focusing at the center of the output scene, but focusing degrades for points away from the focus point. The output scene size for which one can achieve acceptable image quality is a function of platform motion and system parameters (integration angle, range, wavelength, etc.). We quantify how the achievable output image scene size depends on platform motion and SAR parameters, using motion data from an existing SAR testbed. We also quantify the extent to which autofocus can be used to correct for the residual motion compensation errors, using results obtained on actual VHF-UHF SAR imagery.