Multiwavelength Raman lidar - RALI

The Multiwavelength Raman Lidar detects the Raman backscattering radiation from atmospheric water vapor, nitrogen, and Mie / Rayleigh backscattering radiation from atmospheric molecules and aerosol particles.

The laser emission wavelengths are 1064 nm (90mJ), 532 nm (50mJ) and 355 nm (60mJ) and the detection channels are 1064, 532 cross, 532 parallel, 355 nm (elastic wavelengths), and 607, 387 and 408 nm (Raman channels). The laser pulse duration is 7-9 ns, repetition rate 10Hz, and the beam diameter between 5.5-7 mm at fwhm. The dynamic range cover 2-15 km depending on atmosphere transmission, with a 3.75 m spatial resolution. The reception has a 400mm Cassegrain telescope with 1.73 mrad field of view, and the system acquisition is both analog and photon counting, with a 20 MS/s analog sampling rate and 250 Mhz photon counting count rate.

The output parameters are the backscatter coefficient, the extinction coefficient, water vapor mixing ratio (for 407 nm), particle depolarization ratio (for 532 nm).