Estimating ocean surface velocity and coherence time using multichannel ATI-SAR systems

Conventional along-track interferometric synthetic aperture radars (ATI-SAR s) derive the ocean surface velocity from an estimate of the phase differen ce between the SAR echoes received from two displaced phase centres with a single time-lag. The authors propose an efficient asymptotic maximum likeli hood (ML) algorithm for jointly estimating the ocean surface velocity and o cean coherence time by using multichannel SAR data collected front an array of phase centres with multiple rime-lags. The method combines a covariance matching algorithm with the use of the extended invariance principle (EXIP ). Simulated results show that the proposed technique provides better estim ation accuracy than the conventional two-channel system. Moreover, it provi des unambiguous velocity retrieval and flexibility to varying ocean coheren ce time.