Integrated Measurement of Naval Sonar Operations and Precise Cetacean Locations

David Moretti | Naval Undersea Warfare Center

RC-201304

Objectives of the Demonstration

The objectives of this project were to integrate: (1) a real-time sonar detector into existing passive acoustic Navy range marine mammal monitoring systems and (2) a Fastloc™ Global Positioning System (GPS) into a remotely deployed medium-duration satellite dart tag suitable for attachment to a beaked whale (family Ziphiidae). In combination, the goal was to enable the opportunistic medium-term (weeks to months) monitoring of the reaction of cetaceans including sonar-sensitive Blainville’s (Mesoplodon densirostris) and Cuvier’s (Ziphius cavirostris) beaked whales to Mid-Frequency Active (MFA) sonar operations with a high degree of spatial precision not currently available with medium-term satellite tags. The research sought to enable precise documentation of the extent of animal exposure to anthropogenic sound including MFA sonar. These data, including precise localizations, measured sonar exposure, and the presence or absence of deep foraging dives before, during, and after sonar exposure, are critically needed inputs for the Population Consequences of Acoustic Disturbance (PCAD) model being developed to measure the health of animal populations.

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Technology Description

The Marine Mammal Monitoring on Navy Ranges (M3R) system is being used on the major Navy ranges to detect the presence of animals before, during, and after MFA operations. Time intensive analysis of M3R archives is required to determine the time of occurrence of sonar transmissions. This project demonstrated an integrated sonar detector to enable the automatic detection of sonar transmissions. The technologies were validated in both the laboratory and the field. Receiver Operator Curves (ROC) against white noise were measured to validate basic system performance. The software was validated against in-situ data from the Ranges to provide a realistic measure of performance in real-world environments.

The GPS based tag was tested on land at forces that far exceed those expected in the field to verify impact survivability, ballistic performance, and down range accuracy of the delivery system. Dedicated tests to measure the positional accuracy and update rate were completed. GPS tags were placed as follows: three on Cuvier’s beaked whales (Ziphius cavirostris [Zc]), two on fin whales (Balaenoptera physalus [Bp]), three on short fin pilot whales (Globicephala macrorhynchus), and one on a false killer whale (Pseudorca crassidens). The tag was dart attached to individual animals at-sea using a neumatic rifle, and the average tag attachment duration was 19.49 days.

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Demonstration Results

The tag deployments demonstrated that placement of tags on Cuvier’s beaked whales is possible given reasonable sea-state conditions. During the demonstration, the tags had a 0% impact failure rate and met performance objectives for update rates and positional accuracy.

A generic sonar detector was also developed and tested in-situ at the Southern California Offshore Range (SCORE) with mid-frequency active sonar. The detector was integrated into the Marine Mammal Monitoring on Navy Ranges (M3R signal processor) and was capable of monitoring over 200 hydrophones in realtime. It is being used on the three major Navy ranges including the Atlantic Undersea Test and Evaluation Center (AUTEC) in the Bahamas, SCORE, and the Pacific Missile Range Facility (PMRF) in Hawaii.

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Implementation Issues

Existing court mandated monitoring depends heavily on expensive and dangerous aerial line transect surveys. For deep divers such as beaked whales, such surveys offer little hope of measuring the response of the animals to operations or of providing long-term estimates of the cumulative effect of repeated sonar exposure. The technologies outlined by this project, in concert with existing programs, will provide a means of quantifying the longer-term reaction of beaked whales to MFA operations. The systems and algorithms are fully compatible with existing Navy Range signal processors. The technology provides monitoring on a continual 24 hour basis and is far less weather dependent than traditional visual line transect methods. With the integration and transitioning of such technology into range operations, these technologies could complement or supplant the need for continued aerial surveys at a significantly lower cost point with no safety risk.

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Points of Contact

Principal Investigator

Mr. David Moretti

Naval Undersea Warfare Center

Phone: 401-832-5749

Fax: 401-832-4441

Program Manager

Resource Conservation and Resiliency

SERDP and ESTCP

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