Ultra Low Frequency (ULF) Sonobuoy

The US Navy has a requirement for an affordable A-sized sonobuoy with an Ultra Low Frequency (ULF) acoustic sensor. The ULF acoustic band presents an opportunity to detect emissions from submarines, assuming they exist, would be particularly hard for the target platforms to suppress. ULF detection in a free floating sonobuoy configuration poses complications due to motion and flow induced noise. To address the technical challenge of flow induced noise we will develop our ULF sensor concept teamed with UnderSea Sensor Systems, Inc. based on a neutrally buoyant swallow float design. The feasibility study will evaluate two development paths using varying levels of automation. The operator-in-the-loop option would deploy a drifting neutrally buoyant sensor subassembly at the desired sensing depth and employ an acoustic or wired datalink to a floating sonobuoy RF transmitter. The second automated option would package the entire sonobuoy payload as a neutrally buoyant float which will stabilize at the desired sensing depth, and given a target detection of sufficient confidence would employ a pop-up RF transmitter to pass the detection and data report. We will determine the optimum frequency band to exploit target signatures with minimal noise interference, and then determine the appropriate acoustic sensor design.