Submarines have always been designed for stealth. But thanks to ongoing advancements, modern-day vessels can be particularly difficult to detect with common sonar systems. Defence Research and Development Canada (DRDC) is investigating a new technique that could help the Royal Canadian Navy and Royal Canadian Air Force improve their sub-finding capabilities.

Sporting anti-sonar skins and whisper-quiet engines, the latest underwater boats threaten to slip past existing anti-sub warfare (ASW) systems including sonar, which uses sound to detect objects beneath the water’s surface. These days, many defence forces use monostatic or bistatic sonar systems, wherein the transmitters and receivers are located in the same place or in two places (respectively). However, if the equipment isn’t situated in the right location, the sonar network fails to detect the submarine.

DRDC, an agency of National Defence, is looking into a different sort of sonar to help boost the Canadian Forces’ ability to find subs. Known as multistatic active sonar, the technology sees multiple transmitters and receivers working together across a wireless grid. The equipment, situated on naval ships and air force planes, collects data from numerous locations, providing a more complete picture of sub activity than any offered by monostatic and bistatic sonar systems.

DRDC is researching the technology in a multi-year undertaking called the Advancing Multistatic Active Sonar Employment Technology Demonstration Project (AMASE TDP). It intends to demonstrate how multistatic active sonar is better than the stand-alone and passive sonar that has been used in the past. DRDC positions the project as an important evolution in the development of next-generation anti-sub warfare capabilities.

Transmitter-receiver trials
DRDC is conducting the demonstration at its research centre in Dartmouth. Sponsored by the Canadian Forces, the demonstration considers different transmitter-receiver pairings, different ocean environments (shallow or deep water), and new methods for processing and displaying the sonar data.

Multistatic sonar isn’t exactly new. The technology has been available for decades, but forces are only beginning to implement it. The formidable anti-sonar capabilities of the latest subs, plus increased submarine activity, have made forces particularly keen to investigate multistatic systems.

Canada is no exception. According to Adrian Hewitt, the DRDC project manager overseeing the AMASE TDP, the CF needs sonar systems capable of detecting even the quietest vessels.

The project will scrutinize how multistatic sonar can be used with existing and soon-to-be-operational sonar systems employed by the CF. “That’s where the biggest bang for your buck is,” Hewitt said. “Sonar systems are extremely expensive. Whatever we demonstrate, we want to make sure it can be paired with systems that are currently in use or being procured.”

The AMASE TDP received departmental approval this year. Recently, DRDC moved to the next step: planning and engaging the RCN, RCAF and sonar systems manufacturers to ensure the project involves the right mix of experts. The organization is also working with the Forces on a schedule for technology trials. As part of total costs, the AMASE TDP’s $5 million budget includes funding for a trial every year through to 2016.

“You don’t want to spend three years developing something and then try it out just once,” Hewitt explained. “When you experiment early and often, you yield much better results.”

Technology modelling
Once planning is complete, DRDC will move forward with technology modelling, in which the organization uses software to mimic the characteristics of different transmitters and receivers. “Within those various combinations we’ll try to determine a subset that we can scope our demonstrations around,” he said.

Canada’s forces already use a wide array of sonar systems, including hull-mounted and variable depth sonar on Iroquois-class destroyers, Canadian Towed-Array Sonar Systems (CANTASS) on Halifax-class frigates, sonobuoys on major warships (sonobuoys are expendable sonar systems dropped into the water) and tethered sonar on maritime helicopters.

Multistatic sonar may well help the Royal Canadian Navy and the Royal Canadian Air Force augment their current systems for a comprehensive view of submarine activity. With the AMASE TDP, DRDC could play an important part in ensuring that future sonar systems can keep pace with the advanced features of modern subs.

Stefan Dubowski is a freelance writer in Ottawa (