UDT 2020 Designing a Persistent Virtual Maritime Border Megeney 1 , - PDF document

UDT 2020 Designing a Persistent Virtual Maritime Border Presentation/Panel UDT 2020 – Designing a Persistent Virtual Maritime Border Megeney 1 , Lowe 2 1 Hilary Megeney, BMT, Ottawa, Canada 2 Geoff Lowe, BMT, Ottawa, Canada Abstract — In order to ensure sovereignty in territorial waters and sovereign rights in the exclusive economic zone, the proposed persistent virtual maritime border is capable of continuous underwater surveillance over large geographical regions. The system exploits existing sonobuoy technology and enhances it with two-way communications, independent power generation, and improved autonomy, enabling the formation of a scalable surveillance network. The Virtual Maritime Border has the capability to persistently detect, track and classify underwater threats. 1 INTRODUCTION requires a separate channel and each aircraft requires a highly skilled operator to monitor the channels. 150 countries have a coastline which borders the World Exploiting existing sonobuoy technology and Ocean and are susceptible to maritime undetected enhancing it with satellite communications, independent underwater threats. As maritime tensions mount, these power generation, and improved autonomy enables the coastal countries are recognizing the need for effective formation of a scalable surveillance network. The countermeasures to protect and monitor the approach to persistent Virtual Maritime Border is the solution to vulnerable shore side infrastructure, ports, and waterways overcome these challenges and provide continuous and to ensure sovereignty in territorial waters and monitoring of subsurface threats over large geographical sovereign rights in the exclusive economic zone. regions. Encroachment by submarines and unmanned underwater vehicles goes largely undetected and is becoming more 2 SYSTEM DESCRIPTION prevalent with technological advancements in air independent propulsion and autonomy. Persistent The persistent Virtual Maritime Border is a network of surveillance in these regions has become essential in surveillance buoys equipped with active and passive sonar successfully countering subsurface threats. technology, sonar receivers and processing equipment, The most widely used method of detecting satellite communication equipment, rechargeable battery underwater threats is the deployment of sonobuoys. These packs and wave energy conversion technology. The expendable, waterborne sensors are air-dropped from success of the system hinges on its ability to quickly detect, planes or ejected over the side of surface ships, by the process and communicate threats over a large area of hundreds. Sonobuoys were developed in World War II coverage with sufficient independent powering to suit (WWII) in response to the enemy submarine threats autonomous operation for months on station. disrupting the Allied shipping routes. The design consists The system consists of two types of buoys; smaller of a cannister containing underwater acoustic sensors and sonar buoys and larger central processing buoys. The a surface radio transmitter that deploys underwater after scalable system is deployed with central processing buoys being dropped. The aircraft, equipped with a radio and sonar buoys arranged in a grid. Arrays of hydrophones receiver, would patrol the area and interpret the on the sonar buoys will detect and locate potential threats. information received from the sonobuoys. With The acoustic data collected is transmitted to a receiver on technological advancements since WWII, todays the central buoy for processing and classification sonobuoys are much more sophisticated. They can be according to a preloaded library of acoustic signatures. equipped with active sonar and process data from multiple The receiver utilizes satellite communications to send sonobuoys before transmitting to the aircraft receiver. status updates and full acoustic data once a target in the However, current sonobuoys are powered by either classification library is detected. The system schematic is saltwater activated magnesium or silver chloride, lithium shown in figure 1. chemistry, or thermal batteries, are designed to scuttle after usable or selected life expires. With a typical usable life of up to 8 hours, this technology is not capable of providing a persistent surveillance solution. The area of surveillance coverage is also limited by the number of radio channels available onboard the aircraft. It can only be scaled with additional aircraft and personnel, as each sonobuoy

UDT 2020 Presentation/Panel UDT Extended Abstract Template The satellite communication and continuous monitoring requires a constant power supply. The introduction of independent power generation eliminates the usable or selected life expiration faced by the systems utilized today. A wave energy converter (WEC) is integrated into each buoy to provide this power. The WEC is utilized to charge battery packs which in turn power the buoys. The battery banks store energy to reliably supply equipment despite the intermittent nature of wave energy. Two converter types are required for the system. A smaller converter is utilized to meet the lower power requirements of the sonar buoys while a much higher output converter is employed to meet the power demands of the processing buoy. When required to conserve energy due to reduced wave activity, the system cycles power to components to reduce Fig. 1. System Schematic the average power consumption. The cycle schedule is such that the system is active for long enough periods to 3 APPROACH ensure that potential targets are detected before they leave the detection area. Persistent surveillance over large geographical regions is The power management system is designed for three achieved through an expandable configuration, sending primary operating modes: and receiving data between platforms, on site data - Normal Mode – This mode includes all sonar buoys processing, and a reliable electrical power supply, storage passively listening full time with the sonar receiver and management. A robust design is required to ensure operating continuously. The low-bandwidth, low- survivability. It must endure the harsh, unpredictable power consumption satellite system sends periodic forces of winds, waves and currents for many months on status updates and the active sonar buoys can ping station, and little to no maintenance. The system will also occasionally if requested. be vulnerable to marine traffic and wildlife, biofouling, as - Low Power Mode – The sonar buoys and sonar well as constant ambient noise. receiver operate on a 20% duty cycle to reduce power The system is to be deployed in a grid or “trip line” draw. The low-bandwidth, low-power consumption configuration. The configuration allows for better satellite system sends periodic status updates, but it reliability for detecting, locating and tracking potential is assumed that no ping requests will be sent to threats. It also offers redundancy as the failure of one unit conserve power. This mode is expected to be used has minimal impact on the system. Finally, the when it is necessary to conserve energy and prolong configuration allows for flexible coverage and ease of battery life. expansion. For each central processing buoy deployed an - Target Detected Mode – This mode assumes all sonar additional 31 sonar buoys may be deployed to increase the buoys are passively listening full time with the sonar area of surveillance coverage. buoy receiver operating continuously. The high- High speed and high capacity satellite communication bandwidth, high power consumption satellite dish is is required for relay data between platforms. It will also operational to transmit sonar buoy data to a remote enable interaction with a human operator in real time and operator. Frequent pings from the active sonar buoys sending and receiving re-tasking commands. To help are anticipated. This mode is expected to be utilized minimize power consumption, the satellite communication infrequently for minutes or hours when a target is will consist of two systems: a low-bandwidth, low-power detected in the area. The battery will be able to supply consumption transceiver for short status updates and a this relatively short surge even though the wave high-bandwidth, high-power consumption transceiver for energy converter may not be able to produce this relaying acoustic data when a target is detected. level of electrical output on a continuous basis. The acoustic data collected by the sonar buoys is transmitted to a sonar receiver on the central buoy. In addition to the lightweight receiver, the central buoys 4 CONCLUSION house processing equipment and offers multistatic processing of 32 passive or active sonar signals, tracking Continuous underwater surveillance is achievable through algorithms, target classification, and data recording. The the virtual maritime border. It is a scalable, autonomous, central buoy operates remotely via a satellite readily deployable and self-powered system. Current communications link with a ground station operator. The underwater surveillance is reliant on a disposable solution processor analyses the data locally, forwarding only the with a usable life measured in hours. The new system relevant data when a target is detected. This processing exploits existing sonobuoy technology and wave energy to minimizes the frequency of data throughput and reduces create a persistent and maintainable solution. The the bandwidth requirement. The reduction in bandwidth expandable network of buoys is designed to detect, track enables the employment of a much smaller satellite and classify subsurface threats. antenna which consumes less power.