LIDAR SYSTEM USING POLARIZATION DISCRIMINATION TECHNIQUES FOR MOLECULAR AIR POLLUTION MONITORING.
Item
-
Title
-
LIDAR SYSTEM USING POLARIZATION DISCRIMINATION TECHNIQUES FOR MOLECULAR AIR POLLUTION MONITORING.
-
Identifier
-
AAI8501149
-
identifier
-
8501149
-
Creator
-
KOKKINOS, DIMITRIOS S.
-
Contributor
-
Samir Ahmed
-
Date
-
1984
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Engineering, Electronics and Electrical | Physics, Atmospheric Science | Environmental Sciences
-
Abstract
-
A differential absorption of scattered energy (DASE) Lidar scheme which used polarization discrimination to distinguish between simultaneously backscattered Lidar return signals at two close lying wavelengths was conceived, analysed, designed and built into a complete Lidar system. The system was then successfully used to first test out critical basic design premises related to atmospheric backscatter processes, and then to demonstrate its practical viability in field measurements of atmospheric Nitrogen Dixoide.;Lidar outputs are emitted simultaneously at two close-lying wavelengths, orthogonally polarized. The output wavelengths correspond to a peak and trough in the absorption spectrum of the pollutant being monitored. The concentration of pollutant is determined by using polarization discrimination techniques to separate and measure the relative attenuations of the Lidar backscattered signals at each of the wavelengths as they traverse the sample region.;The polarization discrimination system was built producing orthogonally polarized laser outputs at two close-lying wavelengths. A similar arrangement was designed for the Lidar receiver, where the separated signals were detected by separate photomultipliers. Measurements on backscatter depolarization, a factor of key importance in the approach used, were then carried out both in laboratory tests and field tests. Atmospheric field tests confirmed theoretical prediction and laboratory tests, and showed depolarization consistent with a picture of 180(DEGREES) backscatter depolarization plus depolarization due to multiple scatter. The latter effect was the predominant one, and could be largely eliminated by reducing the optical receiver aperture to match the 1 miliradian divergence of the outoing Lidar beam.;Under these conditions, the depolarizations measured in backscattered signals were of the order of 1 percent. Because of the relative nature of measurements used in the scheme, it is found that undesirable backscatter depolarization effects can be neglected as a practical source of error in a polarization discrimination DASE Lida system.;Finally field experiments were carried out, to measure, from the laboratory window, concentrations of Nitrogen Dioxide at kilometer ranges over the upper East Side of Manhattan. The results of these experiments, which measured pollution concentrations of low ppm demonstrated the viability of the polarization discrimination DASE Lidar system.
-
Type
-
dissertation
-
Source
-
PQT Legacy CUNY.xlsx
-
degree
-
Ph.D.
-
Program
-
Engineering
