TECHNOLOGY AREAS: Ground/Sea Vehicles, Sensors

ACQUISITION PROGRAM: PMA-264 - Air ASW Systems; PMA-290 - Maritime Patrol & Reconnaissance

OBJECTIVE: Develop an innovative Geomagnetic Reference Sensor System (GRSS) for reducing the magnetic anomaly detector (MAD) band geomagnetic noise in an airborne magnetic detection system like the ASQ-208, ASW-508, or the ASW-233.

DESCRIPTION: Previous investigations have shown that geomagnetic noise is highly correlated in space. This suggests the probability of using Adaptive Noise Cancellation (ANC) techniques to improve MAD performance by providing a signal free reference. Previous tests have shown that as much as 20 db of noise cancellation can be achieved in the MAD band by ANC thus providing improved performance. A novel approach to providing a geomagnetic reference is to use an air droppable, magnetic sonobuoy(s) which can relay the geomagnetic noise reference to the aircraft to improve the performance of MAD sensor on board the aircraft.

During use, the GRSS will need to be far enough removed from the magnetic detection system so that the target signature does not appear in both data sets simultaneously. The GRSS must be capable of accurately determining the geomagnetic noise without significant contamination by other noise sources like motion, geologic and wave noise. Ancillary sensors for reducing contaminating noises are permitted. Novel approaches are encouraged. Proposed solutions will involve a unique sonobuoy design i.e., no magnetic components, better suspension system and/or unique algorithms which will process the data properly in the aircraft.

The GRSS is intended for use in conjunction with both current and future MAD ASW systems. The innovation must exhibit sufficient sensitivity and internal noise reduction to determine the geomagnetic noise to within 10 pT per root Hz in frequency band of 0.01 to 1 Hz. The data will need to be accurately timed for the coherent noise cancellation between the GRSS and MAD ASW systems. The GRSS cost, weight, power, and ease of deployment are all considerations. Surface and in-water systems may be considered.

PHASE I: Develop the detailed specifications for the proposed GRSS that will achieve the weight, size, power, cost, and performance requirements for an A-size (*) sonobuoy. Evaluate its applicability to the ASW mission. Develop a detailed design to meet the requirements and establish the feasibility of designing and fabricating the GRSS breadboard in Phase II.

PHASE II: Fabricate a GRSS laboratory breadboard based on the Phase I results. Demonstrate the integration of all of the ancillary sensors into the system. Demonstrate the specified noise floor in a laboratory environment and coherent noise reduction of the geomagnetic noise using the GRSS in at least one at sea field test.

PHASE III: Design, fabricate and demonstrate an air deployable A-size (*) GRSS. Deploy the GRSS in conjunction with an ASW MAD mission and demonstrate geomagnetic noise reduction.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: A magnetic reference station is required for all high-resolution magnetic survey work.

REFERENCES:
1. R. Wertz and W. H. Campbell, "Integrated Power Spectrum of Geomagnetic Field Variations with Periods of 0.3 to 300 s," Journal of Geophysical Research 81, 5131 (1976).

2. W. H. Campbell, "Geomagnetic Pulsations," Physics of Geomagnetic Phenomena, Vol. II, Academic Press, New York, 821 (1967).

3. J. T. Weaver, "Magnetic variations Associated with Ocean Waves and Swell," Journal of Geophysical Research 70, 1921 (1965).

4. B. D�eniel, "Undersea magnetic noise reduction", Proceedings of International Conference on Marine Electromagnetics, June 1997.

5. R. Swyers, et al "Analysis of Electromagnetic Noise Characterization and Reduction Flight Test Data" NAWCADWAR-96-41-TR, Nov. 1996.

6. Joseph Czika (Ed), "Electromagnetic Noise Reduction and Characterization Task Final Report" prepared for Naval Air Warfare Center Aircraft Division, Warminster PA by TASC 1101 Wilson Boulevard, Arlington VA 22209, Jan. 1996

7. John J Holmes, "Modeling a Ship�s Femomagnetic Signature", Morgan & Claypart Puleshire, 2007.

8. Wallace H. Campbell, "Introduction to Geomagnetic Fields Second Edition, Cambridge University Press, 2003.

KEYWORDS: Geomagnetic Noise; Magnetometers; Magnetic Anomaly Detection; Airborne ASW; Sonobuoy; Sensors

TPOC: (301)342-2537
2nd TPOC: (301)342-2074

** TOPIC AUTHOR (TPOC) **

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