DETECTION OF BURIED OBJECTS IN THE SEABED AT VERY LOW GRAZING ANGLES

摘要

The problem of detecting an object buried in the seabed is studied by means of a simple model. The object is a rigid sphere buried at some depth in the bottom modeled as a fluid half space. The scattered field is determined for all angles, including grazing angles lower than the critical angle when the wave striking the target is an inhomogeneous wave after sub-critical refraction at the water-bottom interface. The analysis shows that the scattered field is considerably changed both in amplitude and in angular distribution when the incoming wave is an inhomogeneous wave. Particularly, there is relative strong scattering in the forward direction and in a broad angle interval near vertical direction. The echo-to-reverberation ratio is discussed using a simple bottom reverberation model based on the small-roughness perturbation approximation.