Unexploded Ordnance (UXO) has emerged as one of the Department of Defense's (DoD) most pressing environmental cleanup problems. In the United States alone, current estimates indicate that more than 900 sites (11 million acres) with varying terrain, foliation, and topography (including 50 underwater sites) potentially are contaminated with UXO. New technologies capable of detecting UXO with high detection rates and low false alarm rates are required to reduce the cost of site cleanup drastically.

The objective of this effort is to design, fabricate, and test a third harmonic radar to determine its efficiency in detecting and discriminating surface and buried UXO of all sizes and types. In addition, the radar also will have the capability to produce high resolution images showing buried UXO locations.

The project is divided into two phases, a ground phase and an airborne phase. The final result of this effort will be a prototype third harmonic radar system hosted on an aircraft for the detection and mapping of surface and subsurface UXO. The critical elements of this UXO detection system are 1) the third harmonic returns; 2) the ability to produce usable images for analysis; and 3) the fusion of this information with that from other sensors.

In FY 1998, activities included the completion of continuous wave (CW) chamber measurements and the generation of a task measurements report. The ultra- wideband (UWB) measurements task made significant progress throughout the year. The impulse high-voltage system was calibrated with good overall repeatability and chamber artifacts werereliably suppressed. Additionally the van-mounted measurement activity also made significant progress during FY 1998. The radar was assembled, upgraded, and tested and Installation of a variable elevation angle antenna system was completed and tested. The antenna system consists of a high-voltage transmit horn with a built-in third harmonic suppression filter and two receive horns, one for the fundamental band and one for the third harmonic band. An upgraded fundamental receiver was assembled for side-by-side (fundamental and third harmonic band) Synthetic Aperture Radar (SAR) imaging.

The immediate benefit to be realized from this effort is a prototype system with a demonstrated capability to detect and locate surface and shallow-buried UXO remotely. If successful, this effort will provide the UXO remediation community with a capacity not now available.