Remote measurement of HCl, CH_4, and N_2O using a single-ended chemical-laser lidar system

Abstract

The applicability of the high energy discretely tuned DF laser for remote measurement of HCl, CH₄, and N₂O has been investigated. A single-ended or monostatic lidar system using radiation backscattered from topographical targets was tested. Selective absorption of the backscattered signal was used to infer concentration of gaseous species. Good agreement was obtained between the lidar measurements and the concentrations determined by in situ measurements in the remotely positioned sample chamber. The lowest measurable material concentration for each gas was inferred from random fluctuations in the measured concentration. Sensitivity of the existing system to HCl, CH₄, and N₂O was found to be 0.05 ppm-km, 6.0 ppm-km, and 0.24 ppm-km, respectively. An N₂O plume was also measured in the open atmosphere between the lidar system and a foliage target to demonstrate system capabilities under typical field conditions. Performance predictions indicate that total burden and range-resolved species concentration measurements are feasible to a range of 10 km or more with commercially available components.