Atmospheric extinction from Raman lidar and a bi-static remote receiver

The scattering of optical radiation in the visible, ultraviolet and infrared regions of the spectrum has a major impact on commercial air traffic and on many military systems. It has become critically important, with modern systems, that the electro-optical environment be properly characterized. Lidar techniques show great promise for describing the electro-optical scattering environment. Most of the past applications of lidar have failed to provide satisfactory results because the techniques have generally focused on measurements of the backscattered radiation at the laser fundamental wavelength. The authors have been able to demonstrate that the rotational and vibrational Raman backscatter can be used to determine the extinction profile through optical scattering regions containing aerosols and cloud layers. They have developed a secondary bi-static remote receiver designed to collect scattering angle and polarization information from a laser remote sensing system. This instrument collects an image of the radiation scattered from the first few kilometers of the atmospheric path to help determine atmospheric particle size distributions. By collecting data at different angles from the laser transmitter, additional information contained in the scattering angle phase function can be obtained. The Raman lidar extinction together with the backscatter phase function and polarization provide information on the particle size distribution that should allow extension of the extinction and transmission calculations to a wider range of wavelengths.<>