Because of the technical challenges created by the water medium, detection technologies and, therefore, the cleanup of underwater unexploded ordnance (UXO) sites have lagged behind technologies and cleanup on land. Munitions of interest can take many forms and may be buried to varying depths beneath the seabed. Underwater UXO sites may consist of various water salinity, depths, and bottom compositions and be littered with buried and unburied UXO as well as debris fields from the long-term use of the training sites. In deeper water, most underwater UXO will be found on the bottom or buried just below the seabed. Where the bottom is composed of deep layers of mud or fine silt, gravitational burial may be expected. Typically, burial can be modeled and predicted with some accuracy.

This project’s objective was to adapt and exploit the capability of a synoptic sensor system, developed under the auspices of a land mine detection program, to detect underwater UXO, including ordnance buried beneath the seabed. This system is termed “synoptic” because it synergistically integrates three simultaneous distinct modes of passive and active sensing with knowledge-based information to create a detection system.

This project tested advanced technologies, originally developed for mine detection under the Synoptic Airborne Multi-Sensor System (SAMSS) program, for underwater UXO detection. Multiple technologies were investigated during the project, including multispectral imaging (MSI), REVEAL (Rapid Efficient Volumetrically-EnAbled Lidar), and lidar shearography.

The synoptic sensor suite was comprised of three main components, tested separately and characterized as to their capabilities to detect buried ordnance, unburied ordnance, bottom features, and environmental parameters. Each sensor exploited a distinct aspect of the physics of light propagation in marine environments. While results from each of the three technologies were promising, additional work is needed to ensure a fused “synoptic” solution can be achieved.

By combining multiple independent methods of detecting proud and buried underwater ordnance, a suite of sensors can achieve detection performance superior to any one sensor alone. Operated together, they may provide enhanced detection probabilities and orders of magnitude reduction of false alarms.