Target shape and material composition from resonance echoes of submerged elongated elastic targets
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Abstract
Back-scattered echoes yield interesting information when scattering from elastic targets, particularly in the resonance region. Generally source and receiver are at the same location for a fixed orientation. If adjustments of the orientation are made over a suitable angular region then it is possible to ascertain symmetries of the target if they exist, particularly if the frequencies are varied over a suitable range of resonances. If observations of axial symmetry are made then it is possible to obtain both the dimensions of the object and the aspect ratio of the object (ratio of length to width). Once this information is obtained it is also possible to obtain information on whether the target is a solid or a shell, and in some cases what the shell thickness is as well as the material properties of the target. This is assuming that the target is in a 'free' environment; that is, the boundaries of the target are not a factor in calculation. Time domain responses for specific pulse types also yield information, and it is easy to see how a series of questions can form the basis of a scenario that can rule out certain targets or lead to a probability (confidence level) that specific targets are present.
