Magnetic tensor gradiometry in the marine environment

We are developing a sensitive magnetic tensor gradiometer for detection of underwater unexploded ordnance (UXO) using high temperature superconducting quantum interference devices (SQUIDs). In parallel with the instrument development, we are looking at the challenges of making electromagnetic field and gradient measurements in electrically conductive seawater. We have been carrying out a theoretical analysis of how the measurements are distorted by the instrument package and developing methods to correct the measurements for this effect. We are also looking at the identification and removal of electromagnetic signals induced by motion of the seawater in the Earth´s magnetic field. This paper will present the progress to date of the theoretical analysis and also look at dipole tracking methods using tensor gradient measurements.