An asymptotic formulation for SAR images of the dynamical ocean surface

摘要

An analytical framework to aid in the interpretation and prediction of synthetic aperture radar (SAR) images of the ocean is developed. Using stationary phase integration, explicit results are derived for high-resolution images including the cross-section modulation on the ocean and the weighting by the curvature of the phase distortion introduced by the wave motion into the backscattered fields. The general formulation demonstrates that SAR images of the ocean are a ‘map’ of the stationary points on the surface as interpreted by SAR. The general formulation is applied to predict the SAR image of a simple two-scale ocean model using Bragg scattering. This work suggests that image formation of the ocean is due to the amplitude process for light winds (large modulations) and by the phase distortion process for high wind speeds (small modulations). Numerical results are obtained for the stationary points of our simple ocean model, and for the first time an actual SAR image of the ocean is predicted. Inherent in this formulation also is the wave number distortion of the dominant wave of the ocean if its phase speed is not negligible compared to the radar platform velocity.