The advent of quiet diesel-electric submarines operating in shallow waters poses a challenge for antisubmarine warfare. These shallow waters, known as the littoral zone, are a particularly difficult area for sonar surveillance, because of the amount of noise and reverberation found close to land. Current work at CMRE focuses largely on multistatic active sonar, a solution to finding and tracking the new generation of silent submarines.

Today, sonar surveillance typically involves a ship towing an active sonar array that includes a transmitter and receiver. This approach, known as monostatic sonar, has limitations in tracking quiet submarines in shallow waters. A promising alternative to monostatic active sonar is multistatic active sonar, which involves multiple entities, or nodes, transmitting signals and receiving echoes in a coordinated effort to gain a more accurate view of the target. The nodes communicate with each other, and sophisticated signal processing software (data fusion) is used to merge the data from all of the different nodes, which can include arrays towed by ships, fixed buoys, and floating buoys.

Above: Monostatic results (left) versus multistatic results (right) show the improvements in sonar data that can be gained through data fusion.

CMRE research has shown excellent results using multistatic sonar systems, and work is underway on including autonomous underwater vehicles (AUVs) in multistatic systems. The Centre’s program takes a three-pronged approach to research: 

• The development of a multistatic system that uses both fixed sonar buoys and mobile sonar devices, including AUVs.
• The communications architecture that allows these devices to communicate among each other.
• A strategy for deploying a multistatic system in a variety of ASW scenarios