Conventional along-track interferometric (ATI) synthetic aperture radar (SA
R) systems derive the ocean surface Velocity from an estimate of the phase
difference between the SAR echoes received from two displaced phase centres
with a single time-lag. A maximum likelihood algorithm is proposed to proc
ess multichannel SAR data from an array of phase centres with multiple time
-lags. The new technique provides better estimation accuracy than the conve
ntional technique, unambiguous velocity retrieval, and extended operational
capability.