SIMULATION OF OCEAN WAVES IMAGING BY AN ALONG-TRACK INTERFEROMETRIC SYNTHETIC-APERTURE RADAR

A two-dimensional (2-D) model for describing the imaging of ocean wave s by an along-track interferometric synthetic aperture radar (AT-INSAR ) is derived, It includes the modulation of the normalized radar cross section by the long waves, velocity bunching, and azimuthal image sme ar due to orbital acceleration associated with long waves and due to t he orbital velocity spread within the AT-INSAR resolution cell (parame terized by the scene coherence time), By applying the Monte-Carlo meth od, AT-INSAR amplitude and phase image spectra are calculated for diff erent sea states and radar configurations, The Monte-Carlo simulations show that velocity bunching affects the AT-INSAR imaging mechanism of ocean waves, and that a unimodal ocean wave spectrum may be mapped in to a bimodal AT-INSAR phase image spectrum due to an interference betw een the velocity term and the velocity bunching term in the AT-INSAR i maging model, It is shown that the AT-INSAR imaging mechanism of ocean waves depends on the ratio of the scene coherence time and the time s eparation between the observations by the two antennas, If this ratio is larger than one, the AT-INSAR phase image spectra are distorted, Fu rthermore, the simulations show that the AT-INSAR phase image spectrum is quite insensitive to the ocean wave-radar modulation transfer func tion, Comparing AT-INSAR with conventional SAR imaging of ocean waves, we find that the azimuthal cut-off in AT-INSAR phase image spectra is shifted toward higher wavenumbers than in conventional SAR image spec tra. This implies that AT-INSAR can resolve shorter azimuthal wavenumb ers than conventional SAR, Thus we conclude that AT-INSAR phase images are better suited for measuring ocean waves spectra than conventional SAR images.