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

Megeney1, Lowe2

1Hilary Megeney, BMT, Ottawa, Canada 2Geoff 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

150 countries have a coastline which borders the World Ocean and are susceptible to maritime undetected underwater threats. As maritime tensions mount, these coastal countries are recognizing the need for effective countermeasures to protect and monitor the approach to vulnerable shore side infrastructure, ports, and waterways and to ensure sovereignty in territorial waters and sovereign rights in the exclusive economic zone. Encroachment by submarines and unmanned underwater vehicles goes largely undetected and is becoming more prevalent with technological advancements in air independent propulsion and autonomy. Persistent surveillance in these regions has become essential in successfully countering subsurface threats. The most widely used method of detecting underwater threats is the deployment of sonobuoys. These expendable, waterborne sensors are air-dropped from planes or ejected over the side of surface ships, by the

• hundreds. Sonobuoys were developed in World War II

(WWII) in response to the enemy submarine threats disrupting the Allied shipping routes. The design consists

• f a cannister containing underwater acoustic sensors and

a surface radio transmitter that deploys underwater after being dropped. The aircraft, equipped with a radio receiver, would patrol the area and interpret the information received from the sonobuoys. With technological advancements since WWII, todays sonobuoys are much more sophisticated. They can be equipped with active sonar and process data from multiple sonobuoys before transmitting to the aircraft receiver. However, current sonobuoys are powered by either saltwater activated magnesium or silver chloride, lithium 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 requires a separate channel and each aircraft requires a highly skilled operator to monitor the channels. Exploiting existing sonobuoy technology and enhancing it with satellite communications, independent power generation, and improved autonomy enables the formation of a scalable surveillance network. The persistent Virtual Maritime Border is the solution to

• vercome these challenges and provide continuous

monitoring of subsurface threats over large geographical regions.

2 SYSTEM DESCRIPTION

The persistent Virtual Maritime Border is a network of surveillance buoys equipped with active and passive sonar technology, sonar receivers and processing equipment, satellite communication equipment, rechargeable battery packs and wave energy conversion technology. The success of the system hinges on its ability to quickly detect, process and communicate threats over a large area of coverage with sufficient independent powering to suit autonomous operation for months on station. The system consists of two types of buoys; smaller sonar buoys and larger central processing buoys. The scalable system is deployed with central processing buoys and sonar buoys arranged in a grid. Arrays of hydrophones

• n the sonar buoys will detect and locate potential threats.

The acoustic data collected is transmitted to a receiver on the central buoy for processing and classification according to a preloaded library of acoustic signatures. The receiver utilizes satellite communications to send status updates and full acoustic data once a target in the classification library is detected. The system schematic is shown in figure 1.

UDT 2020 UDT Extended Abstract Template Presentation/Panel

• Fig. 1. System Schematic

3 APPROACH

Persistent surveillance over large geographical regions is achieved through an expandable configuration, sending and receiving data between platforms, on site data processing, and a reliable electrical power supply, storage and management. A robust design is required to ensure

• survivability. It must endure the harsh, unpredictable

forces of winds, waves and currents for many months on station, and little to no maintenance. The system will also be vulnerable to marine traffic and wildlife, biofouling, as well as constant ambient noise. The system is to be deployed in a grid or “trip line”

• configuration. The configuration allows for better

reliability for detecting, locating and tracking potential

• threats. It also offers redundancy as the failure of one unit

has minimal impact on the system. Finally, the configuration allows for flexible coverage and ease of

• expansion. For each central processing buoy deployed an

additional 31 sonar buoys may be deployed to increase the area of surveillance coverage. High speed and high capacity satellite communication is required for relay data between platforms. It will also enable interaction with a human operator in real time and sending and receiving re-tasking commands. To help minimize power consumption, the satellite communication will consist of two systems: a low-bandwidth, low-power consumption transceiver for short status updates and a high-bandwidth, high-power consumption transceiver for relaying acoustic data when a target is detected. 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 house processing equipment and offers multistatic processing of 32 passive or active sonar signals, tracking algorithms, target classification, and data recording. The central buoy

• perates

remotely via a satellite communications link with a ground station operator. The processor analyses the data locally, forwarding only the relevant data when a target is detected. This processing minimizes the frequency of data throughput and reduces the bandwidth requirement. The reduction in bandwidth enables the employment of a much smaller satellite antenna which consumes less power. 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

• f 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 the average power consumption. The cycle schedule is such that the system is active for long enough periods to ensure that potential targets are detected before they leave the detection area. The power management system is designed for three primary operating modes:

• Normal Mode – This mode includes all sonar buoys

passively listening full time with the sonar receiver

• perating continuously. The low-bandwidth, low-

power consumption satellite system sends periodic status updates and the active sonar buoys can ping

• ccasionally if requested.
• Low Power Mode – The sonar buoys and sonar

receiver operate on a 20% duty cycle to reduce power

• draw. The low-bandwidth, low-power consumption

satellite system sends periodic status updates, but it is assumed that no ping requests will be sent to conserve power. This mode is expected to be used when it is necessary to conserve energy and prolong battery life.

• Target Detected Mode – This mode assumes all sonar

buoys are passively listening full time with the sonar buoy receiver operating continuously. The high- bandwidth, high power consumption satellite dish is

• perational to transmit sonar buoy data to a remote
• perator. Frequent pings from the active sonar buoys

are anticipated. This mode is expected to be utilized infrequently for minutes or hours when a target is detected in the area. The battery will be able to supply this relatively short surge even though the wave energy converter may not be able to produce this level of electrical output on a continuous basis.

4 CONCLUSION

Continuous underwater surveillance is achievable through the virtual maritime border. It is a scalable, autonomous, readily deployable and self-powered system. Current underwater surveillance is reliant on a disposable solution with a usable life measured in hours. The new system exploits existing sonobuoy technology and wave energy to create a persistent and maintainable solution. The expandable network of buoys is designed to detect, track and classify subsurface threats.

UDT 2020 UDT Extended Abstract Template Presentation/Panel

Author/Speaker Biographies

Hilary Megeney is a Naval Architect with BMT. She has completed an array of engineering work on the Royal Canadian Navy fleet including the auxiliary fleet, Kingston Class coastal defence vessels, Halifax Class frigates and the Victoria Class submarines. She also has experience working with autonomous underwater vehicles and in offshore wind energy. Hilary holds a bachelor's degree in Ocean and Naval Architectural Engineering from Memorial University of Newfoundland. Geoff Lowe is an Electrical Engineer with over 8 years of professional experience and over 4 years of experience working within the field of marine electrical engineering. He obtained his Bachelor of Engineering from Concordia University in Electrical Engineering (Power and Energy Option) in 2011 and has been a Professional Engineer since 2016. Geoff has completed an array of electrical engineering work on the Royal Canadian Navy fleet including the Kingston Class coastal defence vessels and the Victoria Class submarines.