Protecting us from evil

The threat of attacks against ships and harbours has led to the development of Cerberus – a new diver detection sonar, by UK based QinetiQ. The attack on the destroyer USS Cole in Yemen in October 2000 revealed a range of threats, not only from small explosives-laden speedboats, but also from divers or small underwater vehicles. More recently, in March this year, Hamas frogmen attacked an Israeli beachfront guard post from the sea and in April oil rigs off the Iraqi coast were targeted by a number of small boats.

The Cerberus unit provides diver detection at a range of around 700 metres and can be deployed as a single unit to provide 360° cover for ship protection by being slung from the side of the vessel. Alternatively, a number of units can be attached to the seabed in a cordon to provide harbour security and channel protection, effectively extending the detection range to one kilometre and beyond.

The US Navy is currently evaluating two Cerberus360 systems. Like many other military and civilian authorities, it is concerned about the threat posed to their ships and ports by small boats or terrorist divers and swimmers armed with explosives. Jon Riddle, QinetiQ’s marine and acoustics sales manager, explains: “Today, a single terrorist diver equipped with a low-cost and low-tech payload could cause huge loss of life and significant military or economic disruption. Cerberus, which is based on leading edge military sonar technology, works automatically, unobtrusively and, vitally, provides the range necessary to allow time to deal with any potential threat.”

The US military are taking quite a pragmatic approach testing the system says Chris Minto, senior sales manager in the business area that looks after Cerberus and all the underwater security products. “They?ve spent the first stage essentially doing a range of technical tests to assess the system?s technical performance and the range it reaches in a controlled scientific environment, as well as looking at the ease of deployment, reliability and ease of maintenance.”

He told The Motor Ship: “The second stage [of testing] involves transferring the system from a fairly sanitary lake side test environment to actually hanging it off an aircraft carrier or similar sized asset and seeing how it works in practice.”

The main technical challenge in safeguarding ships and harbours from such threats has been the difficulty in locating a human diver because of the lack of a strong sonar target return. Extremely limited underwater visibility greatly reduces the effect of underwater surveillance techniques relying on cameras operating in the visible band.

The units carry sonar arrays and signal processing electronics that are linked by cable to a shore station. The systems provide alerts, location confirmation and multiple target tracking and are tuned to deal with the complex environmental conditions that may arise in individual harbours. Cerberus utilises high definition sonar imaging techniques together with a high-resolution 100kHz wideband active search sonar. Optional 300kHz active imaging sonar and a 2-8kHz passive capability to allow threat detection at sufficient range to allow an effective counter-threat response can complement this.

Swimmers have been successfully detected at ranges of 700 metres by a single Cerberus unit during open, shallow water trials. This range can be extended to one kilometre and beyond with carefully placement of a cordon of units. Target classification is also provided, enabling operators to decide on an appropriate response. The sonar return provided by the target when using Cerberus is detailed enough to allow the identification of the distinctive human chest cavity at distances approaching 500 metres. The operator can therefore distinguish between the potential terrorist human diver and similar sized mammals, such as sea lions or dolphins, further reducing false alarms. The Cerberus360 sonar unit currently provides diver detection at ranges of around 800m, which allows up to 25 minutes reaction time to a trained diver swimming at between one and two knots.

Diver detection of this sort is difficult in challenging shallow water environments and ambitious detection ranges and tracking requirements in a small low-cost sonar make it even harder. QinetiQ believes that a layered defence is likely to be the most effective option and it is for this reason, Cerberus360 and allied QinetiQ technologies, such as long range underwater passive surveillance arrays incorporating our groundbreaking fibre optic sensors (OptaMarine) and high definition surface radar (Tarsier) can be integrated to provide a systems solution out to beyond 10km.

The number of units required to protect a harbour depends on the size of the harbour, what is in the harbour and on the temperature of the harbour says Minto. The company would generally carry out an environmental survey of a harbour to work out what type of installation was required. “Typically, in UK waters each individual Cerberus offers a range of detection of somewhere between 500 and 700m,” he says, “so physically they can cover a circle of a diameter of nearly a kilometre and a half. You obviously want some overlap between systems and we designed it so that a single surface unit can cope with a number of networked systems.” This means that between one and five sonars would be able to cover most sizes of harbours. However, the specifics of the harbour and how the protection is to be arranged has to be considered ? a normal harbour with a single entrance point or whether it is an open harbour with a long breakwater.

The system has been designed to be cost-effective. Minto says: “Our work is based on many years of funded research and projects for the Ministry of Defense and the Royal Navy. With the core research being well established, we then use existing technology to produce it at a cost-effective level.” QinetiQ?s current customers are naval customers who are protecting multimillion-dollar assets and people who might want to protect a harbour where these assets might sit.

“Right now it comes down to the balance of perceived threat and the cost of the asset you?re trying to protect,” explains Minto. For commercial interests, this depends on the scale of operations and perception of threat, which is part of the ISPS Code. “Take somewhere like Rotterdam, for example, what would be the effect of a terrorist threat against a single vessel blocking the mouth for a number of weeks?” Minto told The Motor Ship: “There must be ramifications, so at some stage an analyst would be able to tell you at what point it is worth protecting. Certainly for the larger harbours around the world, it is a cost-effective means of delivering protection to a harbour, especially in the case of a harbour mouth area that could be easily covered with a single system.”

He adds: “Though in the early stages, as the system has only just been completed, we hope to declare the first sale ? and make a big fanfare of it ? rather soon.” Most of the interest currently revolves around particular sensitive terrorist threats or naval requirements. n