In the vast expanse of the world’s oceans, monitoring adversaries’ movements has always posed a significant challenge. Recognizing the need for innovative solutions, the Defense Advanced Research Projects Agency (DARPA) introduced the Persistent Aquatic Living Sensors (PALS) program in February 2018. This groundbreaking initiative aims to integrate the power of biology with cutting-edge technology to develop platforms capable of monitoring underwater environments. Led by program manager Lori Adornato, the PALS program holds the potential to revolutionize underwater surveillance, offering unprecedented insights into the activities of both manned and unmanned underwater vehicles.
Challenges to Underwater Surveillance
The Persistent Aquatic Living Sensors program emerged as a response to the limitations of existing surveillance technologies in underwater environments. The world’s vast oceans and seas offer seemingly endless spaces in which adversaries of the United States can maneuver undetected. The U.S. military deploys networks of manned and unmanned platforms and sensors to monitor adversary activity, but the scale of the task is daunting and hardware alone cannot meet every need in the dynamic marine environment.
Despite the progress made in underwater sensor technology, there are persistent limitations in achieving comprehensive spatial and temporal coverage, especially within contested underwater environments. Challenges such as sensitivity, specificity, high costs of sensors and platforms, restricted access to critical areas, and the need for consistent maintenance due to concerns like corrosion prevention, biofouling mitigation, and battery replacement, have hindered the development of sustained and widespread sensing capabilities.
The Vision of PALS
However, DARPA proposes a transformative approach by envisioning organisms themselves as integral sensing elements, potentially offering a groundbreaking solution to overcome these hurdles.
The realm of marine life presents a promising avenue for innovation. With their acute sensitivity to their environment driven by the imperative of survival, marine organisms hold the potential to revolutionize underwater sensing capabilities. Under the aegis of DARPA’s Biological Technologies Office, an ingenious program is underway to harness the innate sensing abilities of these organisms for strategic surveillance in critical water bodies like straits and littoral regions.
The program envisions harnessing the natural capabilities of marine organisms to create sensor systems that can effectively detect the movements of submerged vehicles. By studying the responses of these organisms to the presence of underwater vehicles, the program seeks to capture and interpret the resulting signals or behaviors. These insights can then be relayed through a network of hardware devices, providing invaluable real-time data for surveillance operations.
Exploring Marine Organisms
At the heart of the PALS program lies the exploration of marine organisms, both in their natural state and through modifications. Researchers are working to identify specific organisms that can serve as ideal hosts for sensor systems.
For instance, the remarkable Goliath groupers emit resonating barks that possess tactile as well as auditory dimensions. This distinctive trait becomes invaluable in scenarios where passing submarines might disturb a grouper, prompting it to emit its distinctive vocalization. This signal, even when the submarine’s presence is exceedingly subtle, could be intercepted by underwater listening posts, charting new horizons for unparalleled situational awareness.
By understanding the unique abilities of various marine life forms, scientists can determine which organisms are best suited to interact with and respond to the presence of underwater vehicles. This intersection of biology and technology opens up new possibilities for creating a symbiotic relationship between nature and innovation.
“The U.S. Navy’s current approach to detecting and monitoring underwater vehicles is hardware-centric and resource intensive. As a result, the capability is mostly used at the tactical level to protect high-value assets like aircraft carriers, and less so at the broader strategic level,” Adornato said. “If we can tap into the innate sensing capabilities of living organisms that are ubiquitous in the oceans, we can extend our ability to track adversary activity and do so discreetly, on a persistent basis, and with enough precision to characterize the size and type of adversary vehicles.” This new, bio-centric PALS technology will augment the Department of Defense’s existing, hardware-based maritime monitoring systems and greatly extend the range, sensitivity, and lifetime of the military’s undersea surveillance capabilities.
Unveiling Signals and Behaviors
The essence of the PALS program lies in deciphering the signals and behaviors exhibited by marine organisms in response to underwater vehicles. These signals could include changes in movement patterns, biofluorescence, or alterations in biochemical markers. The challenge is to understand the language of these organisms and translate it into actionable insights. This intricate process involves advanced data analysis and the development of sophisticated hardware capable of capturing and relaying these signals accurately.
Marine species have developed a wide variety of strategies to successfully compete in their natural habitats. The ability to utilize natural biological activity to provide distributed, persistent sensing could greatly expand ocean monitoring capabilities.
Inorganic sensors or sensor nodes contain certain common elements including sensors/actuators, a processor, memory, power and communications. Replacement of electromechanical devices in whole or in part with living sensors proves attractive since the organisms provide data through their natural behaviors. In some cases, signal processing and storage can be performed remotely thereby reducing the need for local infrastructure and maintenance.
Beyond sheer ubiquity, sensor systems built around living organisms would offer a number of advantages over hardware alone. Sea life adapts and responds to its environment, and it self-replicates and self-sustains. Evolution has given marine organisms the ability to sense stimuli across domains—tactile, electrical, acoustic, magnetic, chemical, and optical. Even extreme low light is not an obstacle to organisms that have evolved to hunt and evade in the dark.
Under the DARPA PALS (Persistent Aquatic Living Sensors) program, several innovative technologies are being developed that leverage biology and technology to create living sensors for underwater surveillance. These technologies aim to tap into the natural capabilities of marine organisms and combine them with advanced hardware and data analysis techniques to monitor underwater environments effectively. Here are some key technologies being developed under the DARPA PALS program:
- Organism Selection and Modification: Researchers are studying a variety of marine organisms to identify those that can effectively detect the presence of underwater vehicles. This involves understanding the organisms’ responses to changes in their surroundings caused by the movement of these vehicles. Additionally, there is an exploration of potential modifications to enhance the organisms’ sensitivity to specific signals associated with underwater vehicles.
- Signal Capture and Interpretation: The heart of the PALS program lies in capturing the signals or behaviors exhibited by marine organisms when they encounter underwater vehicles. This could involve changes in their movement patterns, bioluminescence, or alterations in their biochemical markers. Advanced sensor technologies are being developed to accurately capture these signals, which are then interpreted using data analysis techniques to provide meaningful insights.
- Sensor Integration: The program involves the integration of biological sensors with hardware devices. These devices could include underwater platforms, drones, or autonomous vehicles that are equipped to host and communicate with the living sensors. The challenge lies in creating a seamless interface between the living organisms and the technological components to ensure reliable data transmission.
- Data Transmission and Network: The data collected by the living sensors need to be relayed to central command centers or other monitoring platforms. A network of hardware devices and communication protocols is being developed to facilitate real-time data transmission from the underwater sensors to operational units, enabling timely decision-making.
- Interdisciplinary Collaboration: The development of technologies under the PALS program requires collaboration across multiple disciplines. Biologists, engineers, data scientists, and marine researchers are working together to design and refine the living sensors, ensuring that they are effective, ethical, and environmentally responsible.
- Environmental Considerations: As part of the program, there is a focus on understanding the potential impact of deploying living sensors on marine ecosystems. Researchers are considering ethical and ecological aspects to ensure that the technologies developed do not harm the natural environment.
- Hardware Resilience: The underwater environment poses unique challenges for hardware devices due to factors such as pressure, temperature, and corrosion. As a result, technologies are being developed to ensure the durability and resilience of the hardware components hosting the living sensors.
In essence, the technologies developed under the DARPA PALS program aim to create a symbiotic relationship between nature and innovation. By combining the unique sensing abilities of marine organisms with advanced sensor technologies and data analysis techniques, these technologies have the potential to revolutionize underwater surveillance, offering new insights into the movements and activities of underwater vehicles in real-time.
The PALS program aims to leverage the biological maritime ecosystem across a wide array of marine environments, particularly in the shallow-coastal and littoral regions, to find M/UUV targets. It aims to transform existing biology, historically characterized as background noise, into highly content-rich biological signals that can be interpreted to track, classify, and report on the presence of M/UUVs.
The DARPA-funded PALS teams must develop or apply technologies to record stimulus responses from observed organisms, and develop combined hardware and software systems that interpret those responses, screen out false positives, and transmit analyzed results to remote end users. The teams’ solutions will incorporate technologies such as hydrophones, sonar, cameras, and magnetic, acoustic, and kinetic sensors.
Performers on the PALS program may consider organisms from bacteria through macro-organisms as well as multi-organism interactions, and must both:
Technical Area 1 :
Characterize the biological signal: engineer and/or reproducibly observe, understand, and model behavioral response of biological organisms to M/UUVs and confounder objects, including discriminations of like-sized objects at multiple scales
Technical Area 2:
Interpret the biological signal: detect observed unique biological signals and translate these into actionable alert information The PALS effort requires two stages of sensing. In the first, the biological organisms sense the intrusion of an M/UUV or confounder into their environment and respond with an output signal or observable behavior.
In the second stage, a man-made detector system captures and interprets the unique biological signal or behavior generated by the organism(s), making an analyzed result available in the form of distilled alerts. These components will be integrated by the performers into demonstrator systems able to be deployed in a maritime environment, and capable of end-to end system performance through delivery of alerts via commercial satellite link. Ultimately, PALS systems will offer long-endurance, widespread sensory coverage in multiple maritime environments, augmenting and enhancing current detection capabilities.
DARPA favors proposals that employ natural organisms, but proposers are able to suggest modifications. To the extent researchers do propose solutions that would tune organisms’ reporting mechanisms, the proposers will be responsible for developing appropriate environmental safeguards to support future deployment. However, at no point in the PALS program will DARPA test modified organisms outside of contained, biosecure facilities.
DARPA anticipates that PALS will be a four-year, fundamental research program requiring contributions in the areas of biology, chemistry, physics, machine learning, analytics, oceanography, mechanical and electrical engineering, and weak signals detection.
The Power of Collaboration
DARPA’s PALS program thrives on collaboration, bringing together experts from diverse fields to create a holistic approach to underwater surveillance. Biologists, engineers, data scientists, and marine researchers are pooling their expertise to ensure the success of the program. This interdisciplinary collaboration ensures that the development of sensor systems is not only effective but also environmentally responsible, safeguarding marine ecosystems in the process.
The PALS program has been through three phases so far:
- Phase 1 (2020-2021): This phase focused on developing the basic concepts and technologies for the PALS system. The team worked on developing new methods for attaching sensors to marine organisms, and for extracting data from those sensors. They also conducted experiments to test the feasibility of the PALS system in a variety of environments.
- Phase 2 (2021-2022): This phase focused on developing and testing a prototype PALS system. The team worked on improving the performance of the sensors and the data extraction algorithms. They also conducted field trials to test the prototype system in the ocean.
- Phase 3D (2022-2024): This phase is focused on developing and testing a more advanced PALS system. The team is working on improving the performance of the system in terms of range, accuracy, and reliability. They are also working on developing new methods for controlling and deploying the system.
The Phase 3D of the project is focused on developing and testing a prototype PALS system.
The $15.2 million modification to the contract will be used to support the development and testing of the PALS prototype system. The work will be performed by Applied Physical Sciences Corp. (APS) in Groton, Connecticut, and several other locations. The work is expected to be completed in October 2024.
The progress of the PALS program has been very promising. The team has made significant advances in developing new methods for detecting and tracking underwater vehicles using marine organisms. The prototype PALS system has been shown to be capable of detecting and tracking underwater vehicles in a variety of environments.
The next phase of the PALS program is critical to the success of the program. The team needs to continue to improve the performance of the system and make it more robust and reliable. They also need to develop new methods for controlling and deploying the system. If the team is successful, the PALS program could have a significant impact on undersea surveillance.
Five research teams will study the behavior of marine organisms to develop sensors designed to detect and track manned underwater vehicles and drones in strategic waters under a Defense Advanced Research Projects Agency program. The DARPA-funded PALS teams must develop or apply technologies to record stimulus responses from observed organisms, and develop combined hardware and software systems that interpret those responses, screen out false positives, and transmit analyzed results to remote end users.
As part of the PALS program, Northrop Grumman will develop biological sensing hardware that has increased sensitivity for certain sensor modalities, achieving greater range. Artificial intelligence will be applied to observe patterns in the marine environment to help classify targets. Northrop Grumman is partnered with Coda Octopus (Nasdaq: CODA), Duke University, University of Maryland, Baltimore County and the University of Memphis.
A Northrop Grumman-led team under principal investigator Robert Siegel will study snapping shrimps’ acoustics and bioluminescent organisms’ optical activity, while a group under principal investigator Alison Laferriere and led by Raytheon’s BBN Technologies subsidiary will analyze the potential of snapping shrimp for long-range detection and monitoring of underwater vehicles.
DARPA has selected Northrop Grumman for the Persistent Aquatic Living Sensors (PALS) programme under which the company will develop biological sensing hardware using underwater biological organisms to detect underwater threats. “The detection, classification and tracking of undersea objects is a critical military capability and we are excited to work with DARPA to develop this next generation approach,” Monch reported quoting Mike Meaney, Northrop Grumman Vice President, Advanced Missions in May 2019.
The company will develop the hardware with increased sensitivity for certain sensor modalities, and greater range. Artificial intelligence will be applied to observe patterns in the marine environment to help classify targets. Northrop Grumman is partnered with Coda Octopus, Duke University, University of Maryland, Baltimore County and the University of Memphis.
DARPA will also fund teams led by Naval Research Laboratory, Florida Atlantic University and the University of Maryland Center for Environmental Science. The agency will offer financial aid to the Naval Undersea Warfare Center, Division Newport to help build a hydrophone array-based seafloor system designed to detect ambient sound in reef environments.
The teams’ solutions will incorporate technologies such as hydrophones, sonar, cameras, and magnetic, acoustic, and kinetic sensors.
- The team led by Northrop Grumman Corporation, under principal investigator Robert Siegel, will record and analyze acoustics from snapping shrimp and optical activity by bioluminescent organisms. Snapping shrimp snap their claws at super-fast speeds, creating a high-pressure cavitation bubble. The collapse of this bubble creates a loud snapping noise powerful enough to stun prey. Snapping shrimp also use the snapping noise to communicate with other shrimp, and large colonies of shrimp can create a cacaphony of snapping noises. During World War II, U.S. Navy submarines used the din of snapping shrimp colonies to avoid detection entering Japanese harbors.
- The team led by the Naval Research Laboratory, under principal investigator Lenny Tender, will integrate microbial organisms into a sensing platform to detect and characterize biological signals from natural microorganisms that respond to the magnetic signatures of underwater vehicles.
- The team led by Florida Atlantic University, under principal investigator Laurent Cherubin, will record and analyze vocalization cues from goliath grouper in tropical and subtropical environments.
- The team led by Raytheon BBN Technologies, under principal investigator Alison Laferriere, will use snapping shrimp as sources of opportunity for long-range detection, classification, and tracking of underwater vehicles. The system will use the loud, impulsive sounds produced by snapping shrimp as sources of opportunity in a multi-static sonar system—detecting reflections of those sounds off of the underwater vehicle. To enhance performance and versatility, the system will also listen to the underwater soundscape (i.e., the sounds produced by all animals in the environment), utilizing machine-learning algorithms to detect changes in these sounds caused by the intrusion of an underwater vehicle.”
- The team led by the University of Maryland Center for Environmental Science, under principal investigator David Secor, will tag black sea bass with sensors to track the depth and acceleration behaviors of schools of fish that are perturbed by underwater vehicles.
DARPA is also funding the Naval Undersea Warfare Center, Division Newport, under principal investigator Lauren Freeman, to develop a seafloor system that uses a hydrophone array and acoustic vector sensor to continuously monitor ambient biological sound in a reef environment for anomalies. The system will analyze changes in the acoustic signals radiated by the natural predator-avoidance response of coral reef ecosystem biota, which could offer an indirect mechanism to detect and classify underwater vehicles in near-real time.
Here are some of the key accomplishments of the earlier phases of the PALS program:
- Developed new methods for attaching sensors to marine organisms.
- Developed new methods for extracting data from sensors attached to marine organisms.
- Conducted experiments to test the feasibility of the PALS system in a variety of environments.
- Developed a prototype PALS system that is capable of detecting and tracking underwater vehicles in a variety of environments.
- Conducted field trials to test the prototype PALS system in the ocean.
The DARPA Persistent Aquatic Living Sensors program stands as a testament to human ingenuity and the limitless potential of combining biology and technology. As this initiative continues to unfold, it holds the promise of transforming how we monitor and understand underwater environments. By harnessing the inherent capabilities of marine organisms and translating them into actionable data, the PALS program could redefine the future of underwater surveillance. As we look ahead, we can anticipate a world where the secrets of the ocean are unveiled with the help of our aquatic counterparts, leading to enhanced security and a deeper appreciation for the natural world.