This is an overview of the work carried out in the UK on the stand-off detection of liquid contamination. The UK uses a two-stage concept employing LWIR (long wave infrared) reflectance imaging for location followed by Laser Induced Vapour Emission (LIVE) (patent pending) for identification of the material.
Research has been conducted into IR reflectance imaging, using a HgCdTe starring array and broad band source. 2-5mm diameter contaminant droplets were resolved at distances of 5.5 m on both painted plates and asphalt.
Short distances LIVE experiments using CW agents produced characteristic LWIR emission spectra. These spectra show clear differences between VX, GD and HD as well as backgrounds such as oil and water. Droplets were found to vaporise more efficiently from less absorbent surfaces such as metal and asphalt. A pyroprobe (a rapidly heating probe) was used to flash heat 20 μl droplets of HD, which was detected at 1 metre in a previous version of the experiment.
Longer distance experiments were successfully carried out using smaller amounts of simulant at distances of 18 m. This suggests identification of agent at 20 metres should be trivial providing the rapid heating and generation of hot vapour by remote means is successful. Further, the method is rapid: time resolved studies using a spectroradiometer capable of producing 20 spectra/second shows that 1 second data acquisition is sufficient.