Share Email Print

Optical Engineering

Laser Polar Nephelometer for Airborne Measurements of Aerosol Optical Properties
Author(s): G. W. Grams; A. J. Dascher; C. M. Wyman
Format Member Price Non-Member Price
PDF $20.00 $25.00

Paper Abstract

A nephelometer has been developed for airborne measurement of polar scattering diagrams of atmospheric aerosols. The nephelometer light source is a modulated heliumneon laser; a digital synchronous photon counter is utilized to measure scattered-light intensity. The system has been designed for airborne measurements on a pressurized aircraft using outside air ducted through a 5-cm diameter airflow tube; the sample volume is that which is common to the intersection of the collimated source beam and the detector field of view within the airflow tube. The instrument has been flown on the NASA Convair 990 airborne laboratory to obtain data on the complex index of refraction of atmospheric aerosols. Particle sizing devices were operated simultaneously to determine the aerosol size-number distribution. Calculated values of the angular variation of scattered-light intensity were obtained by applying Mie scattering theory to the observed size distribution function and assuming different values of the complex index of refraction of the particles. The calculated values were then compared with data on the actual variation of the scattered-light intensity obtained with the polar nephelometer. The most probable value of the complex refractive index was taken to be that which provided the best fit between the experimental light-scattering data and the polar scattering diagrams calculated from the observed size distribution function.

Paper Details

Date Published: 1 February 1975
PDF: 6 pages
Opt. Eng. 14(1) 140185 doi: 10.1117/12.7971772
Published in: Optical Engineering Volume 14, Issue 1
Show Author Affiliations
G. W. Grams, National Center for Atmospheric Research (United States)
A. J. Dascher, National Center for Atmospheric Research (United States)
C. M. Wyman, National Center for Atmospheric Research (United States)

© SPIE. Terms of Use
Back to Top