Calculation of optimal parameters of an NH3-CO2 lidar

The basic parameters (range, signal-to-noise ratio, and sensitivity) of a lidar using NH₃ and CO₂ lasers are calculated. The principle of lidar operation is based on the differential absorption recording. Absorption spectra of all known Freons are considered in the spectral range 9—13.5 μm and optimal wavelengths suitable for sensing them are determined. It is shown that the NH₃-CO₂ lidar can sense Freons at distances up to 10 km at a signal-to-noise ratio exceeding 10. Sensitivities of the lidar for sensing Freon-11 using various lines of the ammonia laser are calculated. It is shown that remote sensing of Freon-11 at concentrations of the order of 5×10^-6% is possible at distances up to 8.5 km.