Unexploded ordnance (UXO) contamination is a high priority problem for the Department of Defense (DoD). Recent DoD estimates of UXO contamination across approximately 1400 DoD sites indicate that 10 million acres are suspected of containing UXO. Because many sites are large in size (greater than 10,000 acres), the investigation and remediation of these sites could cost billions of dollars. However, on many of these sites only a small percentage of the site may in fact contain UXO contamination. Therefore, a number of wide area assessment (WAA) technologies, including helicopter Multi-sensor Towed Array Detection System (MTADS) magnetometry (HeliMag) technology, have been demonstrated and validated, both as individual technologies and as a comprehensive approach to WAA.
HeliMag technology provides efficient low-altitude digital geophysical mapping (DGM) capabilities for metal detection and feature discrimination at a resolution approaching that of ground survey methods, limited primarily by terrain, vegetation, and structural inhibitions to safe low-altitude flight. The magnetometer data can be analyzed to extract either distributions of magnetic anomalies (which can be further used to locate and bound targets, aim points, and open burn/open detonation [OB/OD] sites), or individual anomaly parameters such as location, depth, and size estimate. The individual parameters can be used in conjunction with target remediation to validate the results of the magnetometer survey.
Developed by the Naval Research Laboratory (NRL), HeliMag technology was transferred to Sky Research (SKY) via a Cooperative Research and Development Agreement (CRADA) in 2005. Since then, SKY has used the technology to characterize more than 100,000 acres at more than 20 sites, including the ESTCP WAA Pilot Program demonstration sites. During this technology transition process, several technical innovations were identified as having the potential to provide greater efficiency, broader applicability, and greater UXO detection capabilities. These innovations were completed, integrated with the HeliMag technology, and demonstrated at the former KPBR, in Albuquerque, New Mexico, as part of this project.
The objectives of this demonstration were to:
A demonstration study was conducted over 586 acres at the Former Kirtland Precision Bombing Range (KPBR) in New Mexico. The area covered overlapped a previous survey with the original system along with a number of ground-based surveys. Two areas were blind seeded with a number of ordnance with calibers ranging from 60 to 155 mm.
The telemetry system worked extremely well, with connectivity maintained for between 70 to 100 percent (%) of the time during each survey event. With this type of performance, removing the sensor operator from the helicopter is a viable option, with associated reduction in the risk and cost of the technology.
Detection performance was evaluated on two seeded sites. The first in the central north area consisted of 40 60 mm mortars and 40 81 mm mortars. With a halo of 1 m, 23% of the 60 mm mortars and 100% of the 81 mm mortars were detected. The poor detection performance on the 60 mm mortars occurred because the sensor ground clearance was too high (approximately 1.8 m) compared to the intended ground clearance (1.0 m).
In the western seed area, the Program Office emplaced 110 seeds in a geologically “challenging” environment. These consisted of a mix of 81 mm and 4.2-inch mortars, 105 mm high explosive anti-tank (HEAT)-rounds, and 105 mm and 155 mm projectiles. With a detection halo of 1.0 m, all items except 3 of 12 81 mm mortars were detected. Each detected anomaly was fit with a dipole model, and an apparent remanence metric was calculated and used to rank the anomalies by UXO likelihood. When using this ranking scheme 99% of the detected seed items occurred in the top 50% of the target declarations.
SNR was improved by a factor of about 18% compared to the previous generation system. The improvement occurred because of increased signal from the denser sampling of the magnetic field and reduced distortion in the signal and superior noise rejection from the new rotor-suppression algorithm.
Poor detection performance on the 60 mm mortars in this demonstration occurred because the sensor ground clearance was too high. Previous operational experience with the precursor system had revealed considerable variability in the flying heights achieved by different pilots. In addition, it is more difficult to get the MD530 helicopter close to the ground than the Bell-206. For future surveys, the modified sensor boom will be mounted on the Bell-206.
As a WAA technology, the Next Generation HeliMag system is subject to the same issues of regulatory acceptance of the methodology as investigated in the WAA Pilot Program. A main challenge of the Pilot Program was to collect sufficient data and perform sufficient evaluation such that the applicability of these technologies to uncontaminated land and their limitations were well understood and documented. Similarly, demonstrating that WAA data can be used to provide information on target areas regarding boundaries, density and types of munitions to be used for prioritization, cost estimation, and planning requires that the error and uncertainties in these parameters are well documented.
Therefore, following successful technology demonstration of the modified HeliMag technology, regulatory acceptance will piggyback on the success of the ESTCP WAA Pilot Program and the overall WAA methodology. This technology will be one more tool in the WAA “toolbox” that provides flexibility for WAA technology selection that can reduce cost of characterization.