Remote Sensing of Ocean Waves and Currents Using AIRSAR Along-Track Interferometry (ATI)

The phase information in along-track interferometry (ATI) SAR images is a measure of the Doppler shift of the backscattered signal and thus of the line-of-sight velocity of the scatterers. This interferometric velocity is the sum of the orbital motion of water particles from the swell, phase velocities of the Bragg waves, and ocean surface currents. While the advent of ATI SAR provided us with a potentially powerful technique for ocean current mapping, the surface currents cannot yet measured exactly from interferometric velocity measurements. In this paper, we will apply a new method of extracting the surface current velocity from multiple-frequency (L& Cband) ATI SAR data. We have tested ATI SAR data that were collected during the PACRIM-II AIRSAR experiment over the Ulsan coast on the southeastern part of the Korean peninsula. Two lines of ATI data were collected at right angle on September 30th, 2000. We have investigated the ocean waves and current features and have retrieved dominant ocean wave spectrum. The dominant wavelength of swell stays constant over most parts of the study area, but the variation of bottom topography refracts the propagation direction of ocean waves. Furthermore, we could differentiate the ocean current and the Bragg wave phase velocities using multiple-frequency (C & Lband) ATI data.