Angular dependence of SAR modulation transfer function for near range travelling ocean waves

Abstract

An attempt has been made to derive a transfer function that relates two-dimensional spectra from SAR and WMR (Wave Monitoring Radar) obtained ocean wave images for a particular case of an almost ideal wind sea and near range direction of propagation. For this purpose the authors have used situ wave data taken at position T10 within the ERS-1 CAL/VAL area south of Haltenbanken, Norway as well as SAR images contained in the ERS-1 SAR.UI16 product. The situ measurements provide calibrated two-dimensional ocean wave spectra in absolute units. The analysis has been done by using appropriate parametrization of the WMR and SAR spectra in the wavenumber-direction space and subsequent least squares regression. The resulting transfer function gives a quantitative estimate of the effect of the SAR azimuthal cut-off on the spectra and appears to be useful for improving the SAR performance with respect to ocean wave measurements. >