Development and Demonstration of ALARM (Airborne Lidar Agent Remote Monitor)

摘要

An airborne wavelength-tunable CO2 differential absorption lidar (DIAL) capable of making simultaneous measurements of atmosphe4ric backscatter and surface-reflected energy has been developed and tested in a series of experiments. A data base of surface returns for a flight track that passed over ocean, farmland, urban, forest and grassland surfaces was collected for various lidar wavelengths and wavelength separations. The data show that highest correlation between two-wavelength surface returns occurs over land surfaces and the highest decorrelation over ocean surfaces-the DIAL sensitivity for detection of chemical agents based on surface returns is significantly better over land than ocean areas. The data also show that the highest decorrelation is associated with the highest reflectivity surfaces of ocean and urban areas, probably a result of specular reflection. The correlation of surface returns decreases with increasing wavelength separation over land areas but is nearly independent of wavelength separation over ocean areas. The airborne DIAL system was demonstrated for mapping the cross-plume gas concentration distribution resulting from a near-surface release of SF6. A new Fourier analysis method was used to improve single pulse-pair signal-to-noise ratios.