MULTIFREQUENCY SAR OBSERVATION OF A SHIP WAKE

The authors have developed a computer simulation to model SAR (synthet ic aperture radar) images of ship wakes for various configurations. Th e model accounts for the surface perturbation produced by a moving shi p and the influence of the sea background. Electromagnetic scattering from the surface is calculated by using a tilted Bragg theoretical mod el in which it is assumed that the small Bragg waves are modulated by the larger scale ambient sea waves and Kelvin wake fluctuations. The s imulation combines the results of hydrodynamic and radar scatter calcu lations to provide SAR images of the backscattering of the ship's wake . It is shown that, in general, a high resolution SAR should perform b etter than a low resolution system. The decreasing resolution is one o f the reasons why so few Kelvin wake observations are made in the Seas at data (1992). So the authors' simulation uses an airborne configurat ion with a spatial resolution achieving a resolution cell of a few squ are metres. Two frequency polarised responses (L- and X-band) to the K elvin wake embedded in the sea clutter are presented. These images sho w that the features are clearly resolved for at least one frequency fo r different polarised channels. Some of these signatures may contribut e to the detection of the ship and help to extract information about i t.