Temperature profiling of the atmosphere from an airborne lidar by dispersion of filtered rayleigh scattering in atomic and molecular vapors

The main focus of this paper is aimed at using dispersion caused by atomic or molecular transitions as a measurement technique to resolve the spectral components of the RayleighBrillouin scattering for a look-down lidar configuration. The motivation is to measure the atmospheric temperature and density profiles below a supersonic aircraft to enable prediction of sonic boom signatures. This paper contains comparisons of the backscattered number of photons collected for a laser shot down at different angles and wavelengths from an aircraft. For lidar operating at 532 nm and 780 nm, we derive the normalized Rayleigh-Brillouin scattering lineshapes from 0-15 Km for every 1 Km. We show the formulae to generate transmission and refractive index profiles of an atomic vapor and apply them to the dispersion of the lidar return light imaged through a rubidium vapor cell containing a single prism and a vapor cell containing six prisms at mounted Brewster’s angles. The dispersion allows the imaging of the Raleigh Brillouin spectrum while simultaneously suppressing scattering from particulates and aerosols. The full width at half maximum points from the Rayleigh-Brillouin scattering can be used to measure temperature. It is also possible to measure wind velocities along the direction of the laser propagation by measuring the Doppler frequency shift of the Mie scattering spectral components. Modeling details of a vapor prism cell and six vapor prism cells are shown, while experiments are done as a proof of concept. Atomic rubidium is used with a single prism vapor cell and molecular iodine is used with a six prism vapor cell.