Harry A. Schenck
[Code 702S), RDT&E Div., Naval Command Control and Ocean Surveillance Ctr., San Diego, CA 92152-7520]
Characterizing bistatic scattering from a target for many angles of incidence is expensive and time consuming even in ideal laboratory conditions, and essentially infeasible in an operational environment. Consequently, extending the value of monostatic data by using it to estimate the bistatic target strength is extremely desirable. Previous efforts to do this have severe limitations or restrictions in their applicability. A new technique that combines numerical modeling and experiment will be described. The crux of this method is to rely on modeling to supply the far-field propagator function that predicts the scattering in any direction when the surface values are known, and to determine the surface values by least-squares approximation from knowledge of the monostatic scattering and the principle of reciprocity which requires the scattering matrix to be symmetric). An example will be shown in which the complete three-dimensional scattering field was estimated for a rigid axisymmetric body given only the monostatic target strength at angles in one plane from 0 to 180 deg. Rules that relate the number of monostatic observations needed to the frequency and the complexity of the target will be described. The extension of this technique to nonrigid scatterers will be discussed.