The potential UXO contamination of nearly 10 million acres of marine and lacustrine environment has facilitated the need for detection technologies suited for underwater deployment. While ground-based sensing methodologies have generated some success when applied to the underwater environment, the fundamental electromagnetic characteristics of marine media will require an alteration of terrestrial paradigm to fully exploit these conventional methodologies. Specifically, there is much evidence that employing electromagnetic modes that are higher in frequency than those typically used in ground based sensing will yield greater range and sensitivity for underwater surveys. We propose to complete an extensive study of the application of relevant electric and magnetic sensing techniques to the complex underwater environment. By fully characterizing these electromagnetic phenomena in the marine environment, we will reveal sensing modalities that will optimize detection of underwater UXO.
The principal objective of this research is to evaluate the information content in the very low frequency/low frequency (VLF/LF) (10 kHz to 1 MHz) range to exploit both magnetic and electric field information for detection, localization, and discrimination of underwater UXO. We will develop potential design strategies for implementing both magnetic and electric field sensors in the marine environment, and we will determine the best arrangement for a potential combined electric and magnetic field sensing system with the goal of sensing fields at 1-4 m standoff over the frequency range 100 Hz to 1 MHz. Fabrication, testing, and evaluation of a prototype underwater electric and magnetic field sensing system will culminate this effort.
Our approach is founded on the basis that the electromagnetic properties of the underwater environment will enable an extension of the useful magnetic sensing frequency range beyond that typically employed in terrestrial applications. This extended frequency band will provide unique information to enhance detection and discrimination of underwater UXO. Furthermore, we believe that measurement of electric fields generated by induced currents in UWO will prove useful for augmenting standoff sensing and improving object localization.
Success of this approach will significantly improve the ability to detect and characterize underwater munitions due to the higher signal-to-noise ratio in the VLF/LF band relative to current underwater electromagnetic induction systems. Furthermore, application of this concept could provide unique and useful information about targets from the addition of electric field sensing. The inclusion of electric field sensing, if proven successful, may offer new features for target parameterization. We also anticipate significant advantages through the combination of electric and magnetic field information.