DON26BZ01-NV006 — High-Gain Directional Low-Frequency Sonobuoy Array

Award Maximum: $140,000 (Base) / $100,000 (Option) Period of Performance: 6 months (Base) + 6 months (Option) Phase Type: Phase I

OBJECTIVE: Develop a high-gain, low-frequency vertical line array of vector sensors capable of long-range passive detection and enhanced signal processing, deployable in an A-size form factor.

DESCRIPTION: To enhance anti-submarine warfare (ASW) detection and directional sensitivity in deep waters, the U.S. Navy requires a high-gain directional, low-frequency (< 500Hz) sonobuoy array, housed in an A-size form factor. It is expected that array gain will be achieved by using modelled and measured vertical noise profiles. The system must leverage novel sensor configurations and array geometries to maximize low-frequency Signal-to-Noise Ratio (SNR) while remaining compatible with existing sonobuoy communication and processing platforms. Advanced beamforming, signal processing, and robust hardware integration are crucial for extended detection ranges and minimized false alarms. Environmental factors like multipath interference, ambient noise, self-noise, and sensor stability must be addressed to ensure reliable performance in contested environments. This sonobuoy will bolster fleet ASW capabilities by delivering superior signal clarity, longer-range detection, and a decisive operational advantage through improved sensor capabilities and operational durations.

The objective is to develop a high-gain, low-frequency vertical line array of vector sensors capable of long-range passive detection and enhanced signal processing, deployable in an A-size form factor.

The system will be deployed from Navy Maritime Patrol and Reconnaissance Aircraft, have capability across multiple operational environments, and will utilize the necessarily varied hardware configurations, passive processing, and frequency characteristics to consistently achieve critical ASW metrics.

The sonobuoy must support deep-water tactical operations. Deployment depths up to 1000' and 8 hours of life is required. The array design will provide 17 dB of gain at the design frequency in a three-dimensional isotropic ambient noise field as a minimum. The maximum saturation level will be 128 dB/µPa at 100 Hz with a total dynamic range of 96 dB. The sensor solution must be low power and fit within an "A" size sonobuoy (4.875-inch diameter x 36-inch length, weight under 40 pounds). Acoustic data sent to the aircraft from each vector sensor shall consist of Omni, Sine, and Cosine data. The communications link must comply with NATO's STANAG 4718. Long term plans include using the array in a persistent sonobuoy.

Work produced in Phase II may become classified.

PHASE I: Establish the baseline sensor requirements working in conjunction with the Navy Technical Point of Contact (TPOC). Perform comprehensive analytical and numerical modeling to define the optimal design of the sensing element and array for achieving the necessary gain using low frequency vertical noise profiles. Conduct trade studies on various sensor technologies, including velocity sensors, to select the most effective array configuration. Environmental noise factors will also be evaluated to determine their impact on overall system performance. Conduct trade studies on passive processing enhancements and adaptive beamforming to maximize detection range at these low frequencies. A proof-of-concept simulation of the acoustal array will be developed to demonstrate the feasibility of the proposed approach, guiding both design decisions and risk mitigation. The Phase I effort will conclude with the generation of a high-level prototype design to be implemented during Phase II, ensuring a clear path from concept to operational capability. Demonstrate materials/software/hardware required for prototype development can be sourced, produced, or obtained within a reasonable timeframe. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Develop and test prototype(s) of the low frequency sensing element and/or acoustical array to verify Phase I performance predictions. Conduct trade studies on passive processing enhancements and adaptive beamforming to maximize detection range at these low frequencies. Quantify key performance metrics through a combination of laboratory and open water testing. Extrapolate the expected performance for the intended mission(s). Work in Phase II may become classified.

PHASE II OPTION OR CATAPULT PHASE II: Identify and develop deployment mechanisms and communication protocols. Design and fabricate an over-the-side deployable sonobuoy prototype rooted in Phase II findings and conduct over-the-side testing in both controlled facilities and actual aquatic environments to validate performance. Integrate beamforming and signal processing algorithms optimized for the low-frequency range. Finalize the design concept by detailing a comprehensive roadmap for Phase III transition. Conduct a study to determine the feasibility of extending the concept to a persistent capability with an operational life of 24 hours or greater.

PHASE III DUAL USE APPLICATIONS: Develop a production-ready design and specification for the Phase II solution and its accompanying algorithms, then proceed with integrated engineering and operational testing of the air-deployed system to verify full operational functionality in Navy-supported scenarios. Demonstrate the system's adaptability and resilience in diverse maritime environments. Upon successful qualification, transition to the Fleet and refine operational parameters through at-sea trials. Explore commercial applications, including marine mammal detection, underwater resource exploration, and environmental monitoring.

KEYWORDS: Anti-Submarine Warfare; ASW; Sonobuoy; Low-Frequency Acoustics; Directional Arrays; Passive Detection; Beamforming; Underwater Sensing