Modeling Sonar Responses of Targets Deployed On or In the Seafloor

Abstract

Document Number: N0001411WX20015 LONG-TERM GOALRecent interest in understanding the potential advantages of nonconventional detection configurations, such as bistatic vs monostatic, has driven efforts to initiate the model refinements needed to study these configurations for simple targets deployed proud or buried on the seafloor. A benchmark quality capability for these targets is utilized so that unambiguous results are available for physical interpretation and analysis, both in laboratory sonar measurements as well as in sonar field tests using the Naval Surface Warfare Center Panama City Division's (NSWC PCD) synthetic aperture sonar (SAS) systems. The long term goal of this effort is to investigate and compare how the physics of a target embedded in a given environment and sensed under different detection modes can affect both target signal-to-noise (SNR) and classification. This knowledge can then be used to improve sonar detection and classification of bottom targets. OBJECTIVESOne objective is to generate high fidelity datasets to help understand carefully controlled measurements in the scale-model sonar test bed operated at NSWC PCD [1], which can be configured to collect SAS target data along both linear and circular tracks. Interest in circular tracks has grown recently because circular SAS (CSAS) processing may provide imagery with better shape resolution for classification purposes. The comparisons made were used to gain insight to the fidelity of data that can be collected in the test bed by helping to separate target from noise phenomena and by helping to interpret target phenomena that might be useful for target classification. Furthermore, the datasets created are used to study the effectiveness of processing algorithms for isolating signal from noise.A second objective this year is to test solutions recently proposed by Waterman [2] for stabilizing the spherical-basis T-matrix for nonspherical shapes at high frequencies. This would yield a more practical T-matrix solution than the spheroidal-basis version [3] currently used for elongated shapes, which can still be limited by how accurately high order spheroidal functions can be computed. APPROACHFor simple near-spherical target shapes proud or buried in a flat ocean bottom, scattering predictions are generated from high-fidelity solutions based on the T-matrix method [4]. Last year [5],