Wide Area Detection and Identification of Underwater UXO Using Structural Acoustic Sensors

Abstract

Standard Form 298 (Rev. 8-98)Prescribed by ANSI Std. Z39.18Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information This new project is exploring the potential for developing a structural acoustics (SA) based sonar methodology for wide area search and identification of underwater unexploded ordnance (UXO). This new approach may have significant advantages over more conventional acoustic approaches, which rely on the formation of high resolution images. These advantages include: diverse set of "fingerprints" leading to low false alarm rates; longer range operation leading to wide area coverage; and low frequency sediment penetration leading to buried target prosecution. A core element of the current project is a comprehensive examination of the scattering levels and features exhibited by typical UXO targets in the SA regime using NRL's state-of-the-art underwater scattering facilities, both laboratory-based and at-sea. We have recently completed the first phase of this data collection using the laboratory-based facility, and these results are reported here. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) SPONSOR / MONITOR'S ACRONYM(S) 9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) SPONSOR / MONITOR'S REPORT NUMBER(S) PROJECT BACKGROUNDMany active and former military installations have ordnance ranges and training areas with adjacent water environments in which unexploded ordnance (UXO) now exists due to wartime activities, dumping, and accidents. These contaminated areas include coastal and inland waters both in the United States and abroad. SERDP goals require the development of innovative technologies able to separate UXO from false targets and to discriminate amongst individual UXO targets themselves. Over time, such geographic areas are becoming less and less remote as the adjacent lands become further developed, and the potential hazard to the public from encounters with such UXO has begun to rise. Presently there exists no sufficiently effective capability to survey such underwater areas and map UXO locations.This new project (SERDP Project MM-1513) is exploring the potential for developing a structural acoustics (SA) based sonar methodology for wide area search and identification of underwater unexploded ordnance (UXO). This new approach may have significant advantages over more conventional acoustic approaches which rely on the formation of high resolution images.Conventional sonar approaches which form images (see Fig. 1 in Project Accomplishments Section) must operate at relatively high frequencies since the image resolution is dire...

Wide Area Detection and Identification of Underwater UXO Using Structural Acoustic Senors: 4th Annual Report to SERDP MM-1513

“…In the first year 7 , a representative UXO target set (target set 1) was identified, and the specific targets obtained from the Aberdeen Proving Grounds. This four target set included a 155 mm artillery shell, a 5 inch rocket warhead, an 80 mm mortar round, and a 120 mm mortar round.…”

“…Also in the third year, targets were seeded in the maritime environment off the coast of Panama City, and acoustic scattering data were collected using an existing rail-based measurement system. In order to allow the structural acoustic identification algorithms to adapt to new site-specific details such as target type/orientation and environmental conditions, the development of a concept drift active learning identification algorithm suitable for UXO was initiated in the second year, and the plan was to test it in the third year off-line using all the data collected in the previous tasks 13 . Research in the fourth year, focuses on the collection of laboratory-grade data sets regarding target burial and vertical orientation, the analysis of these data bases employing advanced multi-path, sediment-based numerical structural acoustic models, and the determination of the impact of these effects on scattering and on the associated structural acoustic features.…”

“…In the previous year 13 , scattering measurements were carried out on several proud UXO targets in St. Andrew's Bay where the water depths were on the order of 30 feet. This past year, the data associated with one of the targets, the 155mm shell, was analyzed with reference to measurements made in the sediment pool facility at much shorter ranges.…”

Detection and Classification of Buried UXO and Determination of Seafloor Parameters in Littoral Environments using Resonance Scattering Sonar

“…In contrast, resonance scattering (also referred to as structural acoustics) sonar applications are currently developed to help detect and characterize proud and partially buried objects (Bucaro et al, 2007a(Bucaro et al, , 2007bHouston et al, 2002, Houston et al, 2009. The frequency range is lower than in the aforementioned application with wavelengths on the same order or somewhat longer than the dimensions of the object (Figure 1b).…”

“…b) Low frequency resonance scattering of waves by a spherical object. The wavelengths of the incidence and scattered waves are comparable to the dimensions of the spherical object (afterBucaro, 2007a).…”