Determination of ocean wave propagation direction by split-look processing using JERS-1 SAR data

The purpose of the present article is to show that the JERS-1 synthetic aperture radar (SAR), primarily designed for global land observation, can be applied to deriving ocean wave spectra and determining the wave propagation direction. Split-look (multilook) processing is used to produce a sequence of individual sub-images of ocean waves. This processing technique has an inherent property that the successive sub-images are formed at different discretely delayed times. Wave propagation direction can, therefore, be determined from a pair of wave images in different looks. The L-band JERS-1 SAR, despite its low signal-to-noise ratio, has an advantage over C-band spaceborne SARs for having a longer integration time, suitable for the wave analysis using split-look processing. Several different methods are applied to the wave data collected near the coasts of Japan, including the methods of look sum (taking the standard Fourier spectrum of look-summed image), spectral sum, spectral phase shift, and cross-correlation function of sub-images.