Computing the Scattering From Slightly Deformed Spherical Shells

A sphere is often used as a target shape for various underwater scattering experiments. The scattering from a sphere is aspect independent (monostatically), and it can be efficiently modeled. Elastic-shelled spheres can have a complicated scattering response due to the various types of waves which can propagate within the shell. In practice, "spherical" targets are rarely perfectly spherical due to the manufacturing process. For example, the shell may be slightly thicker at the top and bottom of the sphere. In this paper, we present a straightforward numerical method to model the scattering from almost-spherical objects. It is assumed that the target is still azimuthally symmetric about the z-axis, but the shell boundary profiles may vary as a function of polar angle. The effect that this angular dependence has on the backscattered spectra is examined for some simple examples.