Estimating the RAR modulation transfer function directly from SAR ocean wave image spectra

A new method for estimating the phase and amplitude of the real aperture radar (RAR) modulation transfer function (MTF) is proposed. Conventionally, in situ measurements of the seastate have been used in connection with SAR estimation of the RAR MTF. However, investigations using synthetic data reveal that the SAR image spectrum for realistic seastates is shaped by the unknown transfer function to an extent that the underlying wave spectral form is not critical. The authors propose a new method using three range going profiles for estimating the RAR MTF directly from SAR ocean wave image spectra. Experimentally, the phase and amplitude of the RAR modulation are computed using ERS-1 data. The phase is typically from 60° to 120° with an amplitude of 12 to 18