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DARPA PALS seeking living sensors , employing marine organisms as Naval surveillance sensors

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 advances in underwater sensor technology, spatial and temporal coverage remains limited, particularly in contested environments. Barriers to persistent, wide-spread sensing include sensitivity/specificity, high sensor/platform costs, limited access to regions of interest, and routine maintenance robustness associated with corrosion prevention, biofouling removal and battery exchange. By reimagining organisms as sensing elements, these obstacles can be largely circumvented, writes DARPA.


Sea life, however, offers a potential new advantage. Marine organisms are highly attuned to their surroundings—their survival depends on it—and a new program out of DARPA’s Biological Technologies Office aims to tap into their natural sensing capabilities to detect and signal when activities of interest occur in strategic waters such as straits and littoral regions. Goliath groupers, for example, make booming barking sounds that can be felt as well as heard. If a passing submarine disturbs a grouper, causing it to bark, that vocalization could be picked up by an underwater listening post no matter how quiet the submarine is.


DARPA introduced in February 2018 the Persistent Aquatic Living Sensors program in an effort to integrate biology into new platforms meant to monitor adversaries’ movements in underwater environments. The Persistent Aquatic Living Sensors (PALS) program, led by program manager Lori Adornato, will study natural and modified organisms to determine which ones could best support sensor systems that detect the movement of manned and unmanned underwater vehicles. PALS will investigate marine organisms’ responses to the presence of such vehicles, and characterize the resulting signals or behaviors so they can be captured, interpreted, and relayed by a network of hardware devices.


“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.


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.


Persistent Aquatic Living Sensors (PALS) program

The Biological Technologies Office (BTO) of the Defense Advanced Research Projects Agency (DARPA) has requested innovative ideas and approaches to support development of new sensing capabilities in the surface and subsurface marine environment through observation and interpretation of organismal behavior. 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.


However, evaluating the sensing capabilities of sea life is only one of the challenges for PALS researchers. Performer teams supporting DARPA will also have to develop hardware, software, and algorithms to translate organism behavior into actionable information and then communicate it to end users. Deployed hardware systems operating at a standoff distance of up to 500 meters must collect signals of interest from relevant species, process and distill them, and then relay them to remote end users. The complete sensing systems must also discriminate between target vehicles and other sources of stimuli, such as debris and other marine organisms, to limit the number of false positives.


Adornato is aiming to demonstrate the approach and its advantages in realistic environments to convey military utility. “Our ideal scenario for PALS is to leverage a wide range of native marine organisms, with no need to train, house, or modify them in any way, which would open up this type of sensing to many locations,” Adornato said.


DARPA seeks novel concepts to form living sensor elements based on organismal function, behavior, and response to environmental stimulus. Output signals from the organisms should provide actionable information for surveillance operations. The addition of remotely accessible living sensors will greatly increase maritime awareness while reducing risk to US assets.


DARPA wants response in one or more of the followings topics related to potential approaches:

1) Sensor and sensor network conceptual design.

2) Concept of operation.

3) Methods to use energy emitted from an organism or groups of organisms as the input signals to new sensing or imaging modalities.

4) Techniques to understand and utilize avian olfaction and/or marine chemoreception to detect compounds or phenomena of interest.

5) Means to convert marine species migration patterns, settlement strategies, or other life cycle travel including magnetic field orientation, into tactically useful information for naval operations. Strategies to collect and transmit these data should be considered.

6) Algorithms for translating complex biological sensor data into actionable information while minimizing uncertainty.

7) Methods to transmit data to remote observers using biological means.

8) Techniques to interpret changes in the natural underwater soundscape relative to human activities. Information regarding locating the source of anthropogenic disturbance is particularly of interest.

9) Suggestions for completely novel applications of marine species behavior to defense applications.


Responses shall also identify high-impact, real-world applications for the approaches to change the marine sensing paradigm.

Technical Areas

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.


PALS Awards

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.


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.



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