A fast-response near-infrared tunable diode laser absorption spectrometer for in situ measurements of CH4 in the upper troposphere and lower stratosphere

We describe a near-infrared in situ tunable diode laser spectrometer developed for atmospheric measurements of CH4 in the upper troposphere and lower stratosphere (UT/LS). The instrument is designed to provide fast-response (0.5--1 Hz) measurements and operate autonomously on the NASA WB-57F high-al...

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Bibliographic Details
Published in:Applied physics. B, Lasers and optics Lasers and optics, 2002-09, Vol.75 (2-3), p.183-194
Main Authors: Richard, E C, Kelly, K K, Winkler, R H, Wilson, R, Thompson, T L, McLaughlin, R J, Schmeltekopf, A L, Tuck, A F
Format: Article
Language:English
Subjects:
Absorption spectroscopy
Diode lasers
Diodes
In situ measurement
Lasers
NASA
Stratosphere
Troposphere
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Summary:We describe a near-infrared in situ tunable diode laser spectrometer developed for atmospheric measurements of CH4 in the upper troposphere and lower stratosphere (UT/LS). The instrument is designed to provide fast-response (0.5--1 Hz) measurements and operate autonomously on the NASA WB-57F high-altitude aircraft. A single-mode InGaAsP distributed feedback laser diode operating at 1.6537 *mm scans continuously over the R(3) rotation--vibration transition in the 2*n3 band. We use a direct absorption technique incorporating a custom-designed long path length (252 m) low-volume (3.6 L) astigmatic Herriott cell. The present detection sensitivity is 5X10 molecules cm, corresponding to ~20 ppbv in the UT/LS, with the main limit to instrument precision being background optical interference fringes. In-flight performance is demonstrated by presentation of recent data.
ISSN:0946-2171
1432-0649
DOI:10.1007/s00340-002-0935-3