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Proceedings Paper

Argus: a lightweight TDL instrument to measure stratospheric tracers
Author(s): Hansjuerg Jost; Max Loewenstein
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Paper Abstract

Argus is a two channel, tunable diode laser instrument which measures atmospheric methane and nitrous oxide in the upper troposphere and stratosphere up to an altitude of 32 km using second harmonic detection. Investigations of stratospheric transport from mid-latitudes into the tropics is the current focus of our work which requires high precision and high accuracy data. Argus was designed for use on remotely piloted aircraft or light-payload balloons and weighs less than 20 kg. The two channels each have their own laser, optics, detector and signal processing chains. We sample methane at 3.3 micrometers and nitrous oxide at 4.5 micrometers at a rate of 0.1 Hz. The gas is sampled in a Herriott cell which has a total path length of 18.8 m. Each laser is current- and temperature-controlled by a dedicated microprocessor. We sweep the laser at 10 Hz and record direct absorption spectra during the ramping of the laser current. The lasers are modulated with a 40 kHz sine wave; a phase sensitive amplifier and integrator detects the second harmonic data. The analysis is performed offline by applying direct fits to the measured spectra using the non-linear Marquardt- Levenberg algorithm. We have recently flown Argus and ATLAS together on the ER-2 platform for comparison. Precision of Argus is 0.6% and accuracy is estimated to 4 - 17% increasing with altitude.

Paper Details

Date Published: 25 October 1999
PDF: 8 pages
Proc. SPIE 3758, Application of Tunable Diode and Other Infrared Sources for Atmospheric Studies and Industrial Processing Monitoring II, (25 October 1999); doi: 10.1117/12.366444
Show Author Affiliations
Hansjuerg Jost, NASA Ames Research Ctr. (United States)
Max Loewenstein, NASA Ames Research Ctr. (United States)


Published in SPIE Proceedings Vol. 3758:
Application of Tunable Diode and Other Infrared Sources for Atmospheric Studies and Industrial Processing Monitoring II
Alan Fried, Editor(s)

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