Preliminary Evaluation of LIDAR Techniques for Advance Warning of Biological Threats.

摘要

Equations have been developed to predict the capabilities of laser radar techniques for detection of airborne microorganisms. In order to discriminate threat microorganisms from normal atmospheric contents,optical interactions such as fluorescence and Raman scatter must be utilized. Selected optical properties of microorganisms,mostly bacteria,have been explored. Preliminary experimental results of the ultraviolet and visible optical density,the spectral fluorescence characteristics,and the fluorescence quantum efficiency of microorganisms are reported. The results are corrected for instrument biases and,in general,show characteristic nucleic acid and protein absorption in the ultraviolet while tryptophan and chlorophyll fluorescence are predominant. A preliminary value of 12percent was obtained for the tryptophan quantum efficiency of Escherichia coli. The results are used in the LIDAR equations to predict that the fluorescence technique does have promise of detecting bacteria concentrations of 3 x 10to the 8th power organisms/cubic meters at remote ranges of 1km at night and 500 m in the day. Predictions of Raman scatter capbailities are indicated but not performed pending a contractor's report of Raman cross sections of microorganisms. (Author)