Feasibility of airborne detection of laser-induced fluorescence emissions from green terrestrial plants

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Abstract
Recent experiments conducted with the NASA airborne oceanographic lidar (AOL) have shown that laser-induced fluorescence (LIF) spectral emissions from green terrestrial plants are detectable from a remote platform. A 3-MW peak power frequency-doubled Nd:YAG laser at 532 nm was used from an altitude of 150 m to induce fluorescence from trees, bushes, and grasses growing on a barrier island. A companion 422-nm XeCl excimer pumped dye laser with a controlled maximum output power of 100 kW was used separately on additional passes in order to compare its effectiveness over the same test area. Slant range measurements obtained simultaneously from each laser on-wavelength return pulse provided valuable, comparative elevational information on the heights of plants and variations in terrain along the flight lines. Samples of airborne LIF color spectra obtained with 532-nm excitation and cross sectional profiles are given together with supporting spectral measurements performed on selected plant types with a laboratory laser system. While the results to date are very encouraging, additional laboratory and field tests are required to establish the utility of the airborne LIF technique for measuring the distribution of plant pigments and biomass remotely from an airborne platform.