Standoff detection

Figure 1. US Army s Long Range Standoff Biological Detection System operates off a Black Hawk Helicopter and uses LIDAR to detect changes in particle concentration2.

Quality control on detection equipment presents problems from improvements and modifications to the original instrument to the question of how to check the performance of a deployed instrument. In an airport or seaport environment, screening of cargo remains an unsolved problem. In areas of conflict or terrorism, remote (standoff) detection remains a much sought-after goal [19-20]. 

Existing and Potential Standoff Explosives Detection Techniques , National Research Council, Board on Chemical Sciences and Technology, 2004. 

To our knowledge, this is the first demonstration of a sensor capable of realtime detection of a TNT plume in the marine environment at standoff distances (up to 100 m from the source) while deployed on an autonomous underwater vehicle. The sensor has shown virtually no sensitivity to chemical interferent during testing in the marine environment. While the sensitivity of the detector is excellent, its sensitivity is not adequate at its present state of development to... 

Mine detectors, training, U.S. DoD Handheld Standoff Mine Detection System (HSTAMIDS), Australian Rapid Route and Area Mine Neutralization System. 

The magnetic flux density created by a single transition from lOOg of TNT at a distance of 10 cm is 1.0 fT. Even at only 10 cm distance, the flux density is approaching the detectability limits of the most sensitive magnetometers. The flux density decreases with dr3, severely limiting the detector standoff distance increasing the standoff distance to 1 m decreases the flux density by a factor of 1000. 

Recently, the topic of improvised explosive devices (IEDs) has garnered a lot of attention. IEDs may take the form of roadside bombs, suicide bombers, or vehicle-borne bombs. Roadside bombs share some detection issues with land mines, and in principle, the NQR land mine detectors discussed in the previous section can be used to detect roadside IEDs. However, many IEDs are remotely controlled, and the short standoff distance available with NQR makes IED detection dangerous for the NQR operator. The personnel screening devices already discussed in Section 5.2.3. are applicable to the suicide bomber. 

Simonson et al. [148] demonstrated remote detection of explosives in soil by combining distributed sensor particles with UV/vis fluorescence LIDAR technology. The key to this approach is that the fluorescence emission spectrum of the distributed particles is strongly affected by absorption of nitroaromatic explosives from the surrounding environment. Remote sensing of the fluorescence quenching by TNT or DNT is achieved by fluorescence LIDAR - the emission spectra were excited in field LIDAR measurements by a frequency-tripled Nd YAG laser at 355 nm and the fluorescence collected with a telescope and various detector systems housed in a 10 x 50 trailer. TNT has been detected in the ppm range at a standoff distance of 0.5 km with this system (Fig. 16). An important limitation to this technique is the pre-concentration of the explosives on the sensor particles, which requires the presence of water to facilitate the transport of the explosive from the surface of the soil particles to the sensor particles. 

D. Woolard, T. Globus, E. Brown, L. Werbos, B.Gelmont, and A. Samuels, Proceedings of the 5th Joint Conference on Standoff Detection for Chemical and Biological Defense, Williamsburg, VA (2001). 

Some detection methods, such as a physical search, offer a high probability of identifying the presence of an explosive but suffer from being invasive and time-consuming techniques that can also place personnel in harm s way if the explosive is detonated. Other methods result in a somewhat lower probability of detection but are non-invasive and less time-consuming and offer some standoff protection for personnel. The choice of methods is a decision for the end-user and depends on a variety of considerations. These considerations include ... 

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