Application of a Winch-type Towed Acoustic Sensor to a Wave-powered Unmanned Surface Vehicle

Abstract

Although many countries have focused on anti-submarine warfare for several decades, underwater submarines can hardly be detected by current assets such as patrol aircraft, surface ships and fixed underwater surveillance systems. Due to the difficult conditions of the oceanic environment and the relative quietness of submarines, existing acoustic surveillance platforms are not able to fully cover their mission areas. To fill in the gaps, a winch-type towed acoustic sensor system was developed and integrated into a wave-powered unmanned surface vehicle by the Korea Institute of Ocean Science and Technology. Sea trial tests were conducted to verify manoeuvering, acoustic signal detection, and communication capabilities. During the manoeuvering test, the wave-powered glider successfully moved along programmed waypoints. Despite towing the acoustic sensor system, only 20 per cent of initial electricity was consumed in 20 days. The acoustic sensor was lowered to depths of 100 m -150 m by the winch system, and received signals from an acoustic simulator lowered to depths of 50 m -100 m by RV Jangmok. The continuously simulated tonal signals as submarine noises that were refracted downward could be clearly received and identified by the hydrophone system, from distances of 2 km - 8 km, while it was being towed silently and deeply. In addition, an optical camera provided high-resolution images of surface vessels, allowing integration with acoustic detection of underwater objects. In conclusion, this new platform using a deeply towed hydrophone system is worthy of consideration as an underwater surveillance asset. Future work is required to strengthen inter-asset communication and obstacle avoidance, and to overcome strong currents to make this technology a reliable part of the underwater surveillance network.