These days there is an increasing interest in underwater surveillance systems both for military and non-military applications. There seems to be an increasing fear of saboteurs and terrorists going underwater to reach their vicious goals. Locations to be protected may be naval bases, sensitive installations connected with offshore oil-and gas production and transport, nuclear power plants etc.
Also concern about the pollution status of the subsea environment is creating a demand for monitoring of this environment. Monitoring of water quality and detection of pollutants will be required in sensitive areas and also in larger basins. Both the industry and the authorities will need technology and equipment to monitor the subsea environment.
Underwater acoustic methods lend themselves well to surveillance of the subsea environment. Any object from the largest submarine to the smallest aggregation of living organisms and liquids of acoustic impedance different from that of sea water can be detected. Operating frequency, bandwidth and signal processing must be matched to the type and size distribution of the objects looked for.
In the face of piracy, illegal trafficking and immigration, countries put in place the appropriate means of actions to defend their maritime territory.
Autonomous underwater vehicles (AUVs) have gained more interest in recent years for military as well as civilian applications. One potential application of AUVs is for the purpose of undersea surveillance. But sonar systems still remain the primary surveillance technique for ships and submarines in naval warfare In the case of submarines, Sonars are the eyes and ears underwater. Ocean going platforms being relatively slow moving, airborne surveillance they play a key role in early warning.
Sonar technology
Sonar systems have undergone evolutionary changes from unitary systems to composite systems where fusion of data from multiple sensors makes sonar displays highly user-friendly.
The SONAR systems being the only sensor system that has the capability to overcome the limitations of the underwater environment it provides the capability for surveillance of undersea situation by naval platforms and ultimately provides inputs for launch of weapons to neutralize opposing forces It also enables safe navigation obstacle avoidance and underwater communication Considering its strategic utility for the underwater vessels availability of modern sonar system is critical for navies.
India has come a long way when it comes to the development of indigenous sonar systems.
For an emerging economic power like India with 7600 km long coastline having 90 per cent of its international trade through sea routes, the importance of defending its coastline against threats through superior underwater surveillance capability needs no emphasis. Over the last three decades, DRDO has designed, developed and inducted several sonar systems for the warships and submarines of the Indian Navy to enhance this capability. Surface ship sonars like APSOH, HUMSA, and HUMSA NG, submarine sonars like PANCHENDRIYA and USHUS, TADPOLE sonobuoys for airborne applications are some of the major systems delivered by DRDO and exploited by Navy. Several technologies for the towed array sonar and airborne dunking sonar have also been developed by DRDO.
DRDO has been working very closely with PSUs, private sector industries, and academic institutions for the design, development, production, and induction of sonar systems. With the increasing requirement for sonar systems for the new platforms being acquired by the Indian Navy, the industry has evinced keen interest in absorbing the complex sonar technologies. Riding on the revolutionary changes offered by the computation and communication technologies, and the indigenously developed models for prediction and interpretation of sonar performance in Indian waters, user has gained more confidence in exploitation of these sonar systems.
With the advent of submarine warfare and its impact on Allied forces and supply lines in WWII, the need for timely detection of undersea threats was made a high priority in Anti-Submarine Warfare (ASW). As technology of the time progressed, it was recognized that shore-based monitoring stations were the answer to the problem since they could be made basically impervious to destruction, foul weather, and ambient self-generated noise. With the development of quieter submarines and counter-tactics, newer technologies have been implemented over the years to keep up with the threat. Faster processors, higher capacity storage devices, and “cleaner code” have enabled the advancement of the art of locating undersea threats.
Initially, the US Navy’s Marine Mammal Program which began in 1960 had two goals. First, the Navy wanted to study the underwater sonar capabilities of dolphins and beluga whales to learn how to design more efficient methods of detecting objects underwater, and to improve the speed of their boats and submarines by researching how dolphins are able to swim so fast and dive so deep.
In addition to this research component, the Navy also trained dolphins, beluga whales, sea lions and other marine mammals to perform various underwater tasks, including delivering equipment to divers underwater, locating and retrieving lost objects, guarding boats and submarines, and doing underwater surveillance using a camera held in their mouths.
Dolphins were also used for some of these tasks in the Vietnam War and in the Persian Gulf. The Marine Mammal Program was originally classified, and was at its peak during the Cold War. The Soviet Union’s military was conducting similar research and training programs in the race to dominate the underwater front. At one point during the 1980’s, the US program had over 100 dolphins, as well as numerous sea lions and beluga whales, and an operating budget of $8 million dollars. In 1992, the program became declassified.
Born of a three-way marriage of early Cold War strategic necessity, World War II progress in underwater acoustics, and an extraordinary engineering effort, the Navy’s pioneering Sound Surveillance System-SOSUS-became a key, long-range early-warning asset for protecting the United States against the threat of Soviet ballistic missile submarines and in providing vital cueing information for tactical, deep-ocean, anti-submarine warfare. And although subsequent events-most notably the end of the Cold War-robbed SOSUS of much of its mission, its history remains an object lesson in how inspired, science-based engineering development can lead to extraordinary operational effectiveness.
Later, during the most dangerous phases of that simmering conflict, IUSS gave the United States an unprecedented capability for long-range submarine detection and strategic early warning that we can only envy today in this new era of asymmetric threats.
Advanced surveillance vehicles
These days the US is investing in modern underwater drones to perform various surveillance and detection tasks. Even US is extending its help through an unmanned underwater drone to find out the missing Malaysian airline which is suspected to be crashed somewhere in Indian Ocean.
For that purpose the US is sending a 17-foot-long drone submarine that can descend to 14,700 feet and scour the ocean floor with high-tech sonar equipment and cameras to help search the Indian Ocean for wreckage from the doomed flight. In the past the US Naval Office of Salvage and Diving has used “various types of remotely operated or autonomous vehicles” to help recover black boxes and other key components from downed commercial aircraft.
But the drone, which looks like a yellow torpedo and is known as the Bluefin-21, is far from the Pentagon’s only option for the search. The US military has a growing array of robots, drones and other gadgetry that could help if called upon, and the Pentagon is investing even more money undersea in the future.
The current fleet includes a 6,400-pound underwater craft that allows the Navy to dissect undersea wreckage. It is known as CURV-21, short for cable-controlled undersea recovery vehicle. The eight-foot long, five-foot wide craft is equipped with sonar, and uses seven hand-like manipulators to pick through salvage while recording images on a high-resolution digital still camera and several television cameras. It can operate up to 20,000 feet under water.
There are smaller drones like the Deep Drone 8000 and the Magnum Remotely Operated Vehicle. The Deep Drone weighs 4,100 pounds, and can descend up to 8,000 feet deep. Like the CURV, it is equipped with sonar technology and has manipulators that can lift and move pieces of wreckage. It also is equipped with sonar sensors and cameras, and operated remotely. The Magnum is even smaller, weighing about 3,500 pounds. It is encased by a cage that protects it from debris when operating in strong currents, and deployed using an armored cable from the side of a ship. Once the vehicle is close to its target, it is released from the cage with a 600-foot cable made of Kevlar, the same material used in bullet-proof vests and many combat helmets.
A new generation of underwater vehicles is under development too. In one novel example, the Office of Naval Research is examining “GhostSwimmer” technology developed by Boston Engineering in Massachusetts. The program envisions a fleet of underwater drones that resemble fish, mimicking the motion of a tuna and cutting down on drag. It isn’t clear when aspects of the design could be incorporated into the Navy’s fleet of underwater surveillance drones, but the Pentagon awarded the company a $1.5 million grant in 2008.
Researchers at the Defense Advanced Research Projects Agency, DARPA, are also busy developing new drones, including a “Hydra” program that will include an underwater truck capable of carrying both drone submarines and unmanned aircraft. The vehicles would be used for a variety of missions, including surveillance and countering enemy mines at sea, and small enough for the Navy to drop them off using existing ships, aircraft or submarines. DARPA plans to spend about $29.9 million on Hydra in fiscal 2015, up from $14.9 million this fiscal year.
DARPA also is developing a small underwater vehicle designed to operate in the shallow waters off coastlines as both a drone and with a small crew of sailors on board. It’s known as the Unmanned/Minimally-manned Underwater Vehicle, or UMUV.
The US Navy is interested in new technology under development by DARPA that can help detect enemy diesel-electric submarines using a series of underwater surveillance. The program would rely on a network of underwater satellites, known as subullites, and use sonar and other forms of detection. The program is known as Distributed Agile Submarine Hunting (DASH).
Further, the GTRI (Georgia Tech Research Institute), a recognized leader in innovative and advanced research for unmanned systems, is working on a project called Homogeneous Collaborative Control of Unmanned Underwater Vehicles with Acoustic Communication which is aimed at developing robotic devices that could work cooperatively on a variety of subsurface missions.
According to GTRI officials current unmanned air and ground surveillance vehicles are rarely autonomous. Instead, they’re guided by human operators using joystick-type controls. By contrast, today’s underwater surveillance vehicles have a small amount of autonomy built in - but only because water changes the behavior of radio-frequency (RF) communication, making joystick guidance difficult.
Underwater vehicle autonomy today consists mostly of throwing a vehicle off the back of a boat, having it swim around, gather information and then return. But the GTRI program is aimed at using many vehicles that operate both autonomously and collaboratively.
Such underwater technology could offer both military and scientific applications. For instance, collaborative underwater vehicles might scrutinize a much larger area for enemy mines than current technology can, or might be able to perform highly complex anti-submarine warfare missions.
In oceanographic research, collaborative vehicles could study underwater movement and phenomena over a broader area and with more detail than current tools.
The research team has developed a prototype of the homogeneous collaborative unmanned underwater vehicle. Its shape is similar to a sonobuoy, a sonar device used for decades for submarine detection. Using the dimensions of a sonobuoy - 4 7/8 inches by 36 inches - allows GTRI’s new underwater vehicles to fit existing launchers on aircraft and surface vessels. Ultimately, underwater vehicles could communicate with unmanned air vehicles. In this way, airborne sensors could collaborate with underwater sensors to track a given target.
However there are some challenges which lie ahead for GTRI’s underwater-vehicle team. The project is currently using acoustic communication to link its underwater units. Acoustic energy - the same sound energy used in sonar-is often employed for underwater communication because it travels well in water.
But acoustic communication has a number of drawbacks. For one thing, this technology transmits information at fairly slow data rates. Transmissions requiring high data rates, such as video, are not feasible. In addition, the transmission of acoustic information may be heard through the water channel, eliminating the stealth needed for many military missions.
Consequently, the team at GTRI is also researching the use of radio frequencies for underwater communications.
The drawbacks of RF energy include a tendency for RF signals to weaken rapidly in water. But RF also has many advantages, including high data rates and high propagation speed. Finding the right techniques could allow RF to become the best communications technology for linking an underwater-vehicle swarm together.
RF provides an additional advantage-it crosses the water-to-air boundary. That capability would allow underwater vehicles to collaborate with air vehicles without having to use surface buoys.
New technologies
Many companies around the world have given emphasis on developing modern underwater surveillance systems which are now being deployed by many navies.
South Korean company LIG Nex1 has developed Harbor Underwater Surveillance System (HUSS) is a surveillance system-consisting of a sound locator and other sensors-installed at major ports to detect, identify and track hostile targets infiltrating underwater. A submersible passive sonar system is installed in the open sea to enable early detection of enemy submarines, surface ships and semi-submarine boat while a magneto-acoustic detection device is installed in the inland waterways to detect and track surface ships, submarines, transfer ships and other underwater infiltration. In the inner harbor, high- frequency active sonar, radar and electro-optical detection equipment are used to detect and track special operations forces as well as submarines.
Norway’s Kongsberg has been an international supplier of integrated combat systems for submarines and surface navy vessels, with lengthy experience as a supplier of active and passive sonar systems, including underwater vehicle technology.
Kongsberg Mesotech traces its roots back to 1973 and the development of high-resolution single-beam scanning sonar, prior to its acquisition by SIMRAD and then subsequently by the Kongsberg Group. The earliest and most successful developer of multibeam sonar for diver detection, Kongsberg has a large installed customer base that includes the US Navy, the US Coast Guard Service, and other NATO navies and customers around the world.
Kongsberg Maritime Camera Group is a world leader in providing innovative underwater imaging and CCTV surveillance technology that is built to support the most demanding military, offshore, scientific and maritime applications with more than 25 years’ involvement.
Its Diver detection sonar (DDS) has evolved to accomplish a variety of missions. These systems have multi-mission capability and are easily interchangeable from one type of deployment to another. The DDS9000 series meets the requirements for multi-mission capability. The system can be lowered by a winch cable, tripod-mounted for either fixed-position or mobile deployments. The DDS 9000 series’ sonar head’s weight of less than 200 pounds (90 kg) allows for easy deployment by a small crew. Most importantly, this deployment flexibility is achieved without sacrificing detection performance. DDS systems can be integrated easily into larger C2/C4ISR systems to provide greater situational awareness.
Swedish company Saab’s offering includes solutions for mine hunting, direct engagement, maritime security, underwater surveillance and unmanned missions. All of its underwater security systems are prepared for integration into a network centric environment.
Saab’s contribution to safety and security below the surface comprises a wide range of solutions that cover every contingency in countering these threats.
Saab’s sensor solutions for underwater security are designed for easy adaptation to specific customer needs and requirements, and provides sensor, intercept and command & control capabilities, as stand-alone or integrated solutions.
Their solutions can also integrate Autonomous Underwater Vehicles (AUV) and Remotely Operated Vehicles (ROV) to perform area reconnaissance, surveillance, interceptive actions and inspection missions.
Saab Seaeye UK Ltd manufactures electric powered Remotely Operated Vehicle (ROV) systems for a wide range of professional applications. The range currently extends from the portable and versatile Seaeye Falcon to the revolutionary electric work class Seaeye Jaguar.
All Saab Seaeye ROVs can accommodate a standard range of tools and accessories. Moreover custom design service for special tools and ROVs for any unique application can be provided.
Saab Seaeye also design and manufacture a range of ROV handling systems as well as a choice of Tether Management Systems (TMS), cameras, lights and subsea metal shell connectors.
Saab offers AUV systems designed to operate autonomously and perform long-term missions with great speed of advance and advanced information gathering capability. The vehicles are independent of dedicated platforms and can be launched from a submarine, ship or from shore.
S A de Electronica Submarina (SAES) develops leading underwater battle space electronic equipment to meet the challenges posed in maritime-security, coastal-surveillance and anti- submarine warfare. SAES specialises in the study, design and manufacture of electronics and sonar systems for both military and commercial markets. Its Sonobuoy processing acoustic systems (SPAS) provides the tactical mission system and the acoustic sensor operators with the means to detect, classify, localise, and track submarines and surface ships. This is based on the analysis of acoustic signals acquired by deployed sonobuoys.
SPAS has been qualified for installation on ships, maritime patrol aircraft’s and helicopters. The system is fully integrated with other equipment as sonobuoy receivers, UHF radio, audio recorders and data link to conform a complete ASW subsystem. SPAS works in stand-alone mode or integrated with the platform mission tactical system.
Even Indian labs and companies are putting efforts to produce indigenous underwater surveillance capabilities.
Earlier India had floated a tender and invited proposals from both state-owned and private companies to acquire at least 10 AUVs (autonomous underwater vehicles), which are non- tethered robotic devices driven through water by propulsion systems that are controlled and piloted by onboard computers.
Indian hopes to acquire indigenous manufacturing capability for AUVs and hence had placed conditions for technology transfer under the ‘make‘ category of the Defence Procurement Procedure.
This step will certainly give boost to small companies and some bright engineering students to collaborate on such projects and look toward technical tie-ups with larger firms including DRDO.
Earlier CMERI-the apex R&D institute for mechanical engineering under the Council of Scientific and Industrial Research (CSIR)- developed India’s first indigenous autonomous underwater vehicle. The AUV has been built to operate 150 feet under the sea to map the seafloor and collect sensor-based data. AUV-150 is a cylindrical-shaped carrier with streamlined fairing to reduce hydrodynamic drag. It is embedded with advanced power, propulsion, navigation, and control systems. The final prototype of the 4.8 meter-long AUV-150, with all its on-board subsystems, weighs approximately 490 kg. The vehicle also has positive buoyancy of approximately 30 newton, to facilitate its retrieval in case of a power failure.
AUV-150 is second only to Maya, a small autonomous underwater vehicle developed by the National Institute of Oceanography in 2009.
In recent years, the Visakhapatnam-based Naval Science and Technology Laboratory (NSTL) has fashioned a batch of AUVs from handheld slow-speed ones, to military-class, free-flooded platforms weighing 1.7 tonnes, with the capability to assist in the entire gamut of maritime security, straddling coastal and port defence to deep-sea operations. The 1.7-tonne reconfigurable platform, with an operational depth of 500 metres, can carry payloads of up to 500 kg to accomplish a plethora of operations such as surveillance, sensor deployment, and mine countermeasure, besides delivery of ammunition.
The aim of the AUV is to aid the Indian Navy in surveying waters and help in the deterrence of hostile ships or submarines. The AUV technology will be an essential technology of the future as dependence on ocean resources is increasing. Sabotage or attacks on offshore installations, seaways, ocean-going vessels, seaports, harbors, or nuclear power plants is an ever-increasing threat. The need for autonomous underwater vehicles is already being felt. Autonomous underwater technology and underwater robotics are being vigorously pursued in many technologically advanced countries such as the US, Australia, Germany, Russia, Korea, and Japan. However, India has a long way to go in developing marine robotics and underwater advanced surveillance equipment.
