Current methods for detecting and characterizing underwater ordnance rely heavily on explosive ordnance disposal (EOD)-trained divers for visual inspection and handheld metal detector surveys. These dive teams are highly constrained in duration, depth, cost, and activity by health and safety regulations. While autonomous underwater vehicles (AUVs) provide an alternative, those currently available for marine munitions response operations require well-trained operators and do not allow for real-time awareness of the benthic environment. Additionally, the hydrodynamics and propulsion configurations of commercial AUVs preclude hovering for cued interrogation and very slow or adaptive operation at or very near the sea floor.

The objective of this project is to evaluate innovative technologies required for deploying underwater electromagnetic induction (EMI) sensors from remotely operated vehicles (ROVs). The integration of these platforms, highly accurate navigation and control systems, and a high-resolution electromagnetic array can overcome limitations of current diver-deployed, towed, and unmanned integrated underwater ordnance systems. Specifically, ROV-based sensing enables the positioning of array-based sensors directly over targets of interest.

The multisensor frequency-domain digital EMI array utilizes three differential (quadrupole) receivers and is mounted directly aft of the mini-ROV. This EM system will be mounted directly to a 25 kg mid-size hybrid ROV/AUV system containing an advanced inertial navigation and control system. This hybrid ROV provides a stable operating platform for deployment of the marine EM array and is capable of highly accurate positioning and close and well-controlled standoff from the sea floor. A nonmetallic body and integrated inertial fiber-optic gyro and navigation software control system allow for accurate sensor positioning in deep water (>30m), bottom following, station keeping, and detection of small munitions (<60mm diameter) under varied conditions.

This project will demonstrate the ability to collect high quality EMI data from a commercial mid-size class ROV. Although the performance of the system will depend on the type of environment, bathymetry and bottom conditions, currents, and target type and distribution, the project team anticipates that this system will provide critical capabilities of precise data positioning, terrain following, and high probabilities of detection for underwater munitions.

Demonstration of ROV-based EM array sensing may provide several direct benefits for future marine munitions operations. Effective, practical, and defensible methods for detecting and characterizing underwater ordnance are recognized as one the key advances required to reduce the cost and time required for cleanup of contaminated marine and lacustrine sites. At many sites, ROV-based EM sensing may reduce the cost and health and safety burden currently placed on diver surveys while enhancing the overall awareness of the benthic environment from high quality EM data collected in conjunction with supporting visual and acoustic sensor modalities. Successful deployment of ROV-based EM sensing will demonstrate 1) close and well-controlled standoff from the seafloor, 2) real-time operator situational awareness and dynamic repositioning of sensor arrays, and 3) implementation of EM sensor arrays capable of detecting and discriminating small munitions to greater depths than manned, surface towed, or fully autonomous sensing systems. (Anticipated Project Completion - 2014)