Absolute Calibration of a Laser System for Atmospheric Probing

Abstract

In order to obtain quantitative data on the backscatter function from laser irradiance backscattered from the atmosphere, the ratio of power transmitted to power received must be accurately known. No absolute measurements of power, optical system transmittance, detector quantum efficiency, or electronic gain are necessarily required. The technique of measuring the power ratio by irradiating a smoked or painted target of known diffuse reflectance at a fixed range is used to calibrate a complete lidar system. The relative area of the output power pulse is monitored by a fast response photodiode, and the relative area of the returned pulse is also recorded after passing through a filter of known high optical density. It is essential to control the temperatures of the laser rod and receiver interference prefilter to ensure proper spectral matching. Field experience gained using this technique is described, and examples of calibration measurements and backscatter functions for smog and cirrus clouds are presented.

Application of Elastic Lidar to PM10 Emissions from Agricultural Nonpoint Sources

“…Because the lidar signal depends on the optical scattering properties of the PM and these optical properties vary with particle shape, composition, and particle size distribution as well as PM concentration, the lidar signal must be calibrated to PM 10 mass in order to obtain emission factors directly. Calibration procedures used in the past ( − ) have used hard targets of known reflectivity at close range; but using targets requires attenuation in order to protect the lidar detector. We are developing a new calibration procedure that allows calibration under actual instrument field condi tions.…”

Ocean Backscatter Profiling Using High-Spectral-Resolution Lidar and a Perturbation Retrieval

“…This analysis does not consider the fact that radiometric calibration of the lidar is required if the HSRL technique is not used. Calibration of atmospheric lidar has been an issue for some time [23][24][25], and is an area of ongoing research. For airborne or space-based oceanographic lidar, the use of known targets like homogeneous land surfaces [26] or the sea surface [27] has been suggested, but these approaches add additional constraints on the lidar system to be used in practice.…”

A new lidar inversion method using a surface reference target. Application to the backcattering coefficient and lidar ratio retrievals of a fog-oil plume at short-range

“…For the single-scattering lidar equation, for which light has undergone only one scattering event, the measured backscattered power, at range r, can be written in a general way, viz. by considering both a surface target (Bufton, 1989;Hall and Ageno, 1970) and a volumetric target (Collis and Russell, 1976), as:…”