System Error Analysis of an Airborne Along-Track Interferometric Fmcw SAR for Surface Velocity Estimate

A comprehensive system error source analysis and calibration of an airborne along-track interferometric FMCW SAR for ocean surface currents velocity retrieval is presented. Starting with the observed phase errors from a stationary test site, three major error sources are analyzed and possible calibration approaches are derived. The range-dependent phase offsets are demonstrated to be introduced by the phase imbalance between receive channels and receive antennas of the transceiver. The phase undulations in the along-track direction are likely due to the uncompensated motion errors caused by inaccurate aircraft attitude and velocity measurements. After calibration, most of the system phase errors are removed which greatly improves the accuracy for surface velocity retrieval by ATI-SAR.