Enhanced Sensing for Detailed Surveys in Very Shallow Water
Daniel Brown | Applied Research Laboratory at the Pennsylvania State University
This project addresses the development and demonstration of a detailed survey sensor capable of detection and localization of munitions in shallow water environments. The munitions response problem spans an extremely broad range of targets (bullets to bombs), water depths (swash zone to 35 meters), and aquatic environments (freshwater ponds to open ocean). Additionally, the conditions of the munitions can vary widely depending on factors such as impact damage, corrosion, and biofouling. The wide variability of the problem has been detailed by SERDP across a number of workshops. Addressing the problem of detailed survey across all of these environments requires understanding the complex interactions between the sensor employed, the remediation site’s environment, and the munition’s properties. This project presents a set of objectives, building upon the work in MR-2545, Sediment Volume Search Sonar (SVSS), intended to move SERDP closer to a solution to the problem of detailed survey in water depths less than five meters. This effort aims to enhance the performance and robustness of SVSS by improving the performance of the sonar hardware and the signal processing of the sensor’s data.
This program will continue the development of the SVSS sensor hardware and signal processing algorithms used for image reconstruction to augment and improve its current performance. A new receive array, designed for the purpose of three-dimensional sub-bottom imaging, will be fabricated, integrated, and tested. This receive array will be mated to purpose built analog electronics and high dynamic range digital electronics. This receiving sub-system, combined with the projector system developed under MR-2545, will allow the SVSS to achieve along-track resolution as fine as 3 cm. In addition to the hardware development and integration, this effort will focus on improving the signal processing used for image reconstruction to increase target detectability. The strength of the near normal incidence scattered field can dominate returns from near-surface buried ordnance. In this program, particular attention will be paid to algorithms that can mitigate the influence of specular and diffuse scattering near normal incidence. Additionally, algorithms will be developed to exploit focusing the late time elastic target returns. The focusing of these returns will improve the detectability of manmade targets especially in cases where the target itself may be obscured by elevated interface scattering. The sensor will be tested in a field demonstration at the Sequim Bay test bed developed by the Pacific Northwest National Laboratory. This will provide an assessment of the performance of the SVSS at a site developed independently of this program.
This project addresses the needs for the development of detailed survey sensors for acoustic detection and localization of surficial and buried ordnance. The improved sensor hardware supports detection of munitions in cluttered background by providing finer image resolution. Increased resolution will improve both human and automated image interpretation. The approaches that will be developed for rejecting the near-normal sediment interface response and for late-time elasticreturn focusing will improve target detectability in complex conditions.