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Proceedings Paper

The Mobile Atmospheric Pollutant Mapping (MAPM) System: A Coherent CO, Dial System
Author(s): William B. Grant
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Paper Abstract

CO2 laser systems are particularly useful for remote measurement of atmospheric trace gases because of several factors: 1. many molecular species have absorption features in the 9-11 micron spectral region; 2. the atmosphere is relatively transparent; 3. CO2 lasers are discretely tunable in this spectral region, and are reasonably powerful or energetic. Indeed, CO2 laser systems have been applied to measuring a number of molecular species: water vapor, ethylene, ozone, ammonia, hydrazines , freons, methanol, and sulfur hexafluoride(SF6). While most of this work has been with direct detection, some work has been reported using heterodyne detection. In direct detection, a receiver acts as a "light bucket," detecting photons in a wide bandwidth, typically tens to hundreds of wavenumbers (cm-1 where 1 cm-1 = 30 GHz). In heterodyne detection, the detection region is narrowed to a few MHz by use of a local oscillator laser and RF-detection electronics so that the thermal background radiation is kept to a minimum. Thus, in direct detection, measurements are typically limited to ranges of 1-3 km, while in heterodyne detection, measurements can be made to ranges of 5-10 km. In the sections that follow, the hardware for the Mobile Atmospheric Pollutant Mapping (MAPM) System is described, along with measurement results using it, the absorption coefficients and measurement sensitivities for a number of molecular species, and the factors that limit measurement accuracy and range.

Paper Details

Date Published: 25 July 1989
PDF: 19 pages
Proc. SPIE 1062, Laser Applications in Meteorology and Earth and Atmospheric Remote Sensing, (25 July 1989); doi: 10.1117/12.951877
Show Author Affiliations
William B. Grant, California Institute of Technology (United States)

Published in SPIE Proceedings Vol. 1062:
Laser Applications in Meteorology and Earth and Atmospheric Remote Sensing
Martin M. Sokoloski, Editor(s)

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