Geomagnetic Reference Sensor System (GRSS) for Air Anti-Submarine Warfare (ASW)

A principal limiter of airborne MAD systems is geomagnetic noise. The long coherence length of geomagnetic noise recommends the use of correlation processing against a reference sensor outside the search area for noise mitigation, and an air-deployed buoy-mounted geomagnetic reference sensor system (GRSS) is a convenient operational configuration. This requires small, light, expendable vector magnetometers with sensitivity comparable to the larger, more expensive intrinsic scalar magnetometers used in airborne MAD detection. Sensitivity will be primarily limited by vertical surface motion noise and rotations of the vector magnetometer. Areté Associates and Ultra USSI propose to develop an air-deployable GRSS employing a fluxgate vector magnetometer that will meet or exceed the desired sensitivity of 10 pT per root-Hz over the MAD signal band. Surface motion noise will be minimized by isolating the magnetometer from surface wave motion with a mid-water drogue designed to attenuate mid-frequency surface wave motion, and further mitigated by correlation analysis referenced to surface and sub-surface motion sensors. Rotation noise will be mitigated by configuring the vector instrument as a virtual scalar magnetometer (VSM), employing a coordinated combination of motion compensation, advanced processing, and real-time in-sensor calibration compensation.