Experimental validation of numerical models of 3-D target scattering and reverberation in very shallow water

Abstract

OASES 3-D, a wave theory model of seabed insonification, three-dimensional target scattering, and rough seabed reverberation, has been developed to investigate characteristics of multistatic scattering and reverberation from rippled shallow-water seabeds with buried targets. The model combines a scattering theory based on the method of small perturbations with a seismoacoustic propagation model, allowing for field simulations in arbitrarily stratified ocean environments. The validation of this new modeling framework was a major objective of the GOATS’98 experiment carried out in 12–15-m deep water at Elba in May 1998. Spherical and cylindrical targets were buried at different depths within a 10×10 m area of sandy bottom and insonified by a parametric source. The unique dataset provided by the experiment has been used for both experimental validation of numerical models and identification of features of the 3-D acoustics which distinguish targets from reverberation. The methodology used for estimating the bistatic scattering strength of the targets and the background seabed reverberation from data collected by a moving AUV platform will be described. The performance of the model for predicting scattering from proud and buried targets will be discussed and illustrated by examples including both isotropic and aspect-dependent targets. [Work supported by ONR and SACLANTCEN.]