currently used as the basis for explosives detection and to determine whether other techniques might provide promising research avenues with possible pathways to new detection protocols. This report addresses the following tasks:

• Describe the characteristics of explosives, bombs, and their components that are or might be used to provide a signature for exploitation in detection technology.

• Consider scientific techniques for exploiting these characteristics to detect explosives and explosive devices. Particular consideration must be given to discriminating possible signals from the background and interferents that can be anticipated in real applications.

• Discuss the potential for integrating such techniques into detection systems that would have sufficient sensitivity without an unacceptable false-positive rate. In proposing possible detection protocols, give consideration to trade-offs between desirable system characteristics, including relative ease of implementation.

• Propose areas for research that might be expected to yield significant advances in practical explosives and bomb detection technology in the near, mid, and long term.

Successful standoff explosives technology involves detection of a weak signal in a noisy environment. This background is also often dynamic, so that exemplary performance in controlled laboratory settings may be quite poor performance in the field. The speed with which the detection is performed is a crucial factor when a potential threat is rapidly approaching. Finally, all explosives detection methods both generate alarms in the absence of threat, and do not alarm in the presence of a true threat.

Detection of explosives involves receiving a signal, processing the signal, assessing the results, and ultimately deciding whether explosives are present or not. To assess the performance of a given detection methodology, concepts such as sensitivity (a measure of when a detector alarms if the substance of interest is present) and the receiver operating characteristic (ROC) curves are considered. ROC curves, which plot the probability of detection against the probability of false alarm (and thus combine sensitivity and specificity performance), are of particular interest because they provide a means of comparing two competing detection techniques.

Front Matter (R1-R10)

Executive Summary (1-11)

1 Introduction (12-17)

2 Elements of Detection: Concepts, Threats, and Devices (18-34)

3 Systems of Detection (35-55)

4 Chemical Characteristics of Bombs (56-70)

5 Existing Detection Techniques and Potential Applications to Standoff Detection (71-96)

6 Biological Markers (97-103)

7 Unexploited Potential Bases of Detection (104-116)

8 Summary of Committee Recommendations (117-122)

Appendix A Statement of Task (123-125)

Appendix B Glossary (126-128)

Appendix C Presentations to the Committee (129-138)