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 approximately 3,000 sites (encompassing tens of million acres) with varying terrain, foliation, and topography (including 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. Advances in detecting UXO must be pursued to enable the DoD to continue to conduct training operations in a safe and environmentally friendly manner.

The objective of this project was to advance current radio frequency (RF) tag capabilities to survive the operating conditions associated with munitions, provide information on the munitions location, and minimize the false alarm rate.

The tag must be secured to the candidate ordnance item and be capable of surviving the delivery system and impact. The buried tag must respond to and then signal the interrogation module when the detection system is brought nearby. Several candidate Tag/Interrogator Systems were explored and tested. This project investigated various delivery modes, effects on lethality, implementation costs, modes for safety and security, and tactical deployment issues. Parametric analysis was used to guide the implementation of technologies required to successfully accomplish the overall objective of providing a unique solution to future UXO remediation efforts.

The Electromagnetic (EM) UXO Tag System required significant advancement of the current technology. The DoD requires a custom tag that can be interrogated through several feet of soil using an aboveground mobile interrogator. The two primary issues of concern are the ability to detect a buried tag and the survivability of the tag. The first step in the system design was to establish the performance and operational requirements of both the Tag and the Interrogator. Next, a design was performed to include key factors such as RF frequency selection, tag and interrogator antenna design, and tag size, location, and packaging. Detectability is driven primarily by RF frequency and antenna design along with supporting Tag and Interrogator modulation electronics. Tag survivability was addressed by use of established and documented approaches of electronic component design and packaging techniques. Both laboratory and field-testing were key factors in design verification.

The project team concluded that the testing at the Aberdeen Test Center, Maryland in 2005 and 2006 demonstrated that properly-embedded tags on UXO items can be detected to the needed depth of 3 feet. Fully-developed above-ground interrogators could scan munition ranges at reasonable rates, with a one-meter-wide swath and an estimated speed of 2 to 3 miles per hour. This type of search would provide a high probability of detection. The project team made no attempt to estimate the false alarm rate, but a false alarm would occur only when a munition exploded but did not damage the radio frequency identification (RFID) tag, or when a tag separated from its munition. Ground clutter and munition scrap would not influence the detection probability or the false alarm rate. The major factor in the cost of remediation may be the high false alarm rate of current UXO search methodologies.

Proof of principle for successful detection and location of UXO and munitions that have pre-embedded RF tags was demonstrated in this project. The resulting long-term benefit could be significantly decreased costs of range remediation due to the higher probability of detecting UXO with fewer false alarms. The project team believes a detailed analysis would show the tagged-munition methodology to yield a large overall savings in the future, even though cost would be incurred mounting commercial-off-the-shelf RFID tags on munitions.