A wavelet packet approach for bistatic buried target classification with an AUV-borne synthetic aperture sonar

Buried target detection and classification is of significant interest to the underwater mine countermeasures (MCM) community. In order to penetrate the seafloor, low frequency sources are required. For adequate temporal (cross-range) resolution, a wideband source is necessary. In this low frequency regime, the different scattering mechanisms behave as a strong function of frequency. Buried elastic targets, such as mines, exhibit strong modal behavior, generating responses delayed in time and occupying only a fraction of the full source frequency band. There is also much more sub-bottom interaction by the lower frequencies, and as such the statistics of the reverberation signal vary with frequency. This may impact the platform motion estimation capability in synthetic aperture sonar (SAS) applications. This paper details an algorithm for exploiting the temporal and frequency diversity of the signals for SAS target detection and classification. An example is provided using an at-sea bistatic SAS application with an AUV-borne sonar receiver