L3 Technologies
Hydroacoustic Monitoring

Hydroacoustic Monitoring ConceptThese systems are designed for monitoring of nuclear events. A nuclear explosion generates a very strong source of underwater sound, also known as hydro acoustic waves. The physical characteristics of the oceans form a sound axis channel known acoustically as the Sound Fixing and Ranging (SOFAR) Channel which allows these waves to travel for extremely long distances with little energy loss. For this reason it is possible to monitor the broad ocean areas of the world with only a small number of hydroacoustic stations. A hydroacoustic monitoring system can detect these hydroacoustic waves from remote locations.

Hydroacoustic monitoring systems utilize omni-directional low-frequency hydrophones at the center of the low-loss ocean SOFAR channel. The hydrophone stations monitor at the low frequencies suitable for recording explosions at large distances. The hydroacoustic monitoring system is particularly effective at discriminating between explosions in the ocean and earthquakes, which are the prime source of detected events. Fiber optic cables bring the signal back to a shore station and transmit this information in near-real-time to a centralized data processing center.

These long-life systems utilize design elements common to our undersea defense and ocean science cabled sensor systems. Highly reliable sensors, riser cables, electronics modules, fiber optic transmission modules, pressure vessels, backbone cables, cable sealing and termination technology and deployment packaging are integrated for worldwide complex in-water installations.

The hydroacoustic monitoring systems are deployed in groups of three sensor nodes for redundancy and to measure the direction of the event. System installation is performed at remote sites around the globe, requiring careful attention to logistical planning for successful implementations.

Hydroacoustic System Ready for Deployment. Shown Adjacent to Sister Vessel. Hydroacoustic Node