Effects of Polynomial Plus Power-Law Errors on SAR Refraction Autofocus

Radar pulses are subject to delay and bending as a result of refraction through the earth's atmosphere. Such effects can yield overall scene defocus in synthetic aperture radar (SAR) images, since the amount of delay and bending can vary from one radar pulse to the next along the synthetic aperture due to spatially varying atmospheric conditions. A recent investigation has resulted in SAR autofocus techniques for estimating and compensating for these atmospheric delay and bending effects. The current analysis examines the performance of this autofocus algorithm for cases in which the atmospheric delay and bending are obtained from error profiles along the synthetic aperture which include both polynomial modeling and power-law contributions. Refocus results from the subject atmospheric-based autofocus methods are quite positive when applied to measured Ku-band radar imagery in which known delay and bending errors have been applied.