Using Ship Wake Patterns to Evaluate Sar Ocean Wave Imaging Mechanisms

Book excerpt: The Joint Ocean Wave Investigation Project (JOWIP) was conducted to evaluate the detectability of ocean wave structures on imaging synthetic aperture radar (SAR). This project used Kelvin surface ship wake patterns generated under controlled and well documented surface environmental conditions to isolate SAR image parameters. Use of waves of known wavelength and direction provide the opportunity to evaluate the SAR contribution to ocean wave forecasting. SEASAT-like images made with L-band SAR are presented: (1) to suggest how ship-generated surface roughness combines with the velocity-bunching mechanism in calm ocean areas to produce the unusually narrow wakes observed for azimuth-traveling ships on SEASAT images; and (2) to estimate conditions under which SAR image modulation mechanisms can be expected to produce wake images. A method is described for using the Kelvin transverse ship wake wave component to quantitatively evaluate the contributions of various SAR ocean wave imaging mechanisms. It makes use of the narrow sector of surface roughness generated by a ship along its track to produce SAR images of the longest waves in its wake system on flat calm water.