Midfrequency "Through-the-Sensor" scattering measurements: a new approach

In this paper, a new paradigm for "through-the-sensor" remote sensing of the seafloor is presented. The methodology has been tailored for use with the AN/SQS-53C sonar found on many U.S. Navy destroyers. Sonar beamformer outputs are processed, and a point georeferenced database of signal attributes is constructed. Corresponding sonar settings and ship navigation information are also included for each database point. Database entries are then fused with environmental characteristics, such as bathymetry and sound speed information. These data may be derived from historical databases, on-site measurements, or a combination of the two. The database is then completed by ambiguity resolution and matching of modeled eigenray paths with database entries in order to associate signal attributes with specific propagation paths. Model inputs are derived from a customized version of the Comprehensive Acoustic System Simulation/Gaussian Ray Bundle eigenray propagation model (CASS/GRAB), which performs propagation estimates over incremental range/depth steps. Illustrations of how the point database may be filtered/constrained, gridded, and displayed are presented. An example of how bottom scattering strength can be derived from the database is presented, followed by an example of a technique for monostatic bottom loss estimation. Results indicate that the approach presented in this paper represents a viable method for conducting "through-the-sensor" measurements of seafloor scattering properties