Theory of the double-edge molecular technique for Doppler lidar wind measurement

The theory of the double-edge lidar technique for measuring the wind with m olecular backscatter is described. Two high-spectral-resolution edge filter s are located in the wings of the Rayleigh-Brillouin profile. This doubles the signal change per unit Doppler shift, the sensitivity, and improves mea surement accuracy relative to the single-edge technique by nearly a factor of 2. The use of a crossover region where the sensitivity of a molecular- a nd an aerosol-based measurement is equal is described. Use of this region d esensitizes the molecular measurement to the effects of aerosol scattering over a velocity range of +/-100 m/s. We give methods for correcting short-t erm, shot-to-shot, frequency jitter and drift with a laser reference freque ncy measurement and methods for long-term frequency correction with a servo control system. The effects of Rayleigh-Brillouin scattering on the measur ement are shown to be significant and are included in the analysis. Simulat ions for a conical scanning satellite-based lidar at 355 nm show an accurac y of 2-3 m/s for altitudes of 2-15 km for a 1-km vertical resolution, a sat ellite altitude of 400 km, and a 200 km x 200 km spatial resolution. (C) 19 99 Optical Society of America.