Remote sensing of vegetation stress and soil contamination using CO2 laserreflectance ratios

A tunable CO2 laser reflectance sensor operating in the 9-11 mu m wavelengt h region of the electromagnetic spectrum was used to measure the mid-infrar ed active reflectance characteristics of stressed vegetation and contaminat ed soil. Measurements were performed at various wavelengths, incidence angl es, and polarization combinations. The vegetation study was conducted by in ducing freezing, chilling, drought, flooding, and heat stress on four diffe rent plant species showing varying leaf cover characteristics, The soil stu dy was conducted by adding chemical contaminants, viz., antifreeze, used mo tor oil (containing gasoline), and unused motor oil to bare soil. Reflectan ce ratios, i.e., ratios of reflectance at different wavelengths, were inves tigated as to their relationships with different stresses and contamination s. It was determined that judiciously selected reflectance ratios could be used to identify stressed plants (although the type of stress could not alw ays be identified), as well as the presence and the type of contamination i n bare soil. This indicates the potential for CO2 laser sensors to monitor vegetation stress and soil contamination from standoff platforms.