Marine Survey System for Detection of Unexploded Ordnance

With support from the Strategic Environmental Research and Development Program (SERDP) and Environment Security Technology and Certification Program (ESTCP), SAIC has developed and demonstrated a marine unexploded ordnance (UXO) survey system designed for use in shallow water (<9.1m). The air foil shaped sensor platform has two actuatorcontrolled elevators to control depth, altitude and attitude. The sensor platform incorporates eight cesium vapor magnetometers (0.6-m horizontal spacing) and a time-domain EMI system with a single large transmitter coil and an array of four receiver coils. The sensor platform is towed by a 9.1-m pontoon boat (with a 22-m cable), which houses the data acquisition system and auxiliary electronics required for controlling and monitoring the sensor platform. The sensor platform has two operating modes: altitude mode for maintaining a constant altitude above the bottom; and depth mode for maintaining a constant depth below the water surface. The attitude and depth of the sensor platform is controlled by an autopilot, which feeds output commands to the starboard and port actuators. The autopilot uses attitude information (pitch, roll, and yaw) from a tactical grade inertial measurement unit (IMU) on the sensor platform, velocity data from a real-time-kinematic (RTK) GPS system, heading from the sensor platform magnetic compass, altitude above the bottom from the platform sonar altimeter and water depth from the platform pressure sensor. The data acquisition system uses a separate GPS unit for synchronization of the system PC clock to GPS UTC time. The system’s first demonstration was at the former Duck Naval Target Range. Approximately 121.4 hectares were surveyed in water depths of 1-4 meters using the magnetometer and EMI sensor arrays. An overall target location accuracy of +/30 cm was achieved. A total of 100 targets from the 500 target dig list were reacquired and recovered by UXOqualified divers. Approximately 50% of the recovered targets were UXO items associated with the former range. Additional surveys have been completed in Ostrich Bay (Puget Sound), Lake Erie(Ohio), bays around Vieques and Culebra islands,( Puerto Rico) and in the Potomac River (off Blossom Point, MD).