Extremely Low Frequency (ELF) for Anti-Submarine Warfare (ASW)

The US Navy has a requirement for an affordable A-sized independent sonobuoy with an Extremely Low Frequency (ELF) magnetic field sensor suitable for operation in both deep and shallow water regions. The 0.5 to 30 Hz ELF band presents an opportunity to detect galvanic current from submarines, especially those which are poorly maintained. ELF sensors have been used in fixed mounted applications, however free floating sonobuoy configurations pose complications due to motion induced noise, control of sensor orientation, and miniaturization. To address the technical challenge of motion induced noise we propose to develop our ELF sensor concept teamed with UnderSea Sensor Systems, Inc. which senses horizontal flow and repositions the drogue and ELF sensing element to a stagnation point. Whole field magnetometers will eliminate the need for precise orientation of the sensors. Additionally we will use of multiple ELF sensing elements to correlate and discriminate far-field geomagnetic noise.