Field trials for standoff bio-aerosol detection

Joint field trials have been arranged by FOI in Umeå with the purpose of measuring fluorescence and backscattering radiation with standoff detection system under well controlled circumstances. Teams with lidar systems from both FOI and Førsvarets Forskningsinstitutt (FFI) from Norway participated in the trials during the time period 15-26 September 2008. Biological agent simulant particles and interferents were released in the air and in a container arrangement allowing for a well defined particle concentration along a 12 meter test path 230 meters away from the lidar systems. The particle concentration was continuously monitored using various particle counters and slit samplers. FOI evaluated both a pulsed 1550 laser system for cloud monitoring by elastic backscattering and a fluorescence lidar with a laser wavelength of 355 nm. The FFI team tested their 355 nm fluorescence lidar. This report summarizes FOI and FFI results from the trials. Some important conclusions were that the infrastructure and the equipment developed for field trials of biological standoff systems worked as planned and that the released aerosol clouds were relatively easily classified by spectral analysis of laser-induced fluorescence. The results so far indicate that a high average output power level is an important system requirement. Laser pulse energies exceeding 100 mJ is desirable. The spectral resolution of detection can however be reduced without loosing the classification capability.