Measurement of the magnetic signature of a moving surface vessel with multiple magnetometer-equipped AUVs

Abstract Measurement of the magnetic signature of naval vessels allows one to determine their vulnerability to mines, and thus whether the signatures must be reduced. Hypothetically, a formation of magnetometer-equipped AUVs could be used to perform a magnetic signature measurement. In this work, a formation of three magnetometer-equipped AUVs was used to assess the feasibility of performing a magnetic signature measurement on a moving surface vessel. The AUVs used localization from acoustic transponders fixed to the bottom, data contained in acoustic communications, an inertial measurement unit, and other onboard sensors to navigate during the experiments. A surface vessel with a fiberglass hull was outfitted with a permanent magnet at the bow, and directed to travel on a straight course. The AUVs navigated in the opposite direction, passing underneath the surface vessel. Position estimates for individual magnetic field measurements using AUV-acquired navigation data were found to be accurate to within an average of 1.2 m. Magnetic fields of 100–300 nT were clearly measured, consistent with the 5–10 nT noise floor of the AUV/magnetometer unit. In the measurements that were performed, total uncertainty in signature measurement was estimated to be ∼250 nT in the presence of a magnetic field gradient of ∼200 nT/m.