25 October 1999 Development of a tunable diode laser instrument for airborne in-situ measurements of carbon monoxide (CO) and nitrous oxide (N2O)
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Abstract
We have developed an instrument to fly on the NASA WB-57F aircraft which measures simultaneously two atmospheric tracers, CO and N2O. These gases have lifetimes which make them appropriate dynamical tracers in the upper troposphere and lower stratosphere. To measure these species for studies of current interest we need a continuous record with a sensitivity of about 1 ppbv, and an absolute accuracy of about 1 percent. To trace the effect of small scale features requires a response time around 1 second. We describe the details of a tunable diode laser-based instrument designed for automatic operation aboard the WB- 57F aircraft at altitudes between the surface and 65,000 feet. A single diode laser, cooled by liquid nitrogen, is used to provide radiation at absorption lines of CO (2190.018 cm-1) and N2O (2190.350 cm-1). Fully reflective optics directs the infrared beam through a long pass cell (36 m path length) of small volume (0.3 l) operated at relatively low pressure (40 mb). The instrument operates autonomously for up to 8 hours. Calibration is achieved by the introduction of standard, calibrated mixtures into the inlet sample flow.
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James W. Hannigan, James W. Hannigan, M. T. Coffey, M. T. Coffey, William G. Mankin, William G. Mankin, } "Development of a tunable diode laser instrument for airborne in-situ measurements of carbon monoxide (CO) and nitrous oxide (N2O)", Proc. SPIE 3758, Application of Tunable Diode and Other Infrared Sources for Atmospheric Studies and Industrial Processing Monitoring II, (25 October 1999); doi: 10.1117/12.366443; https://doi.org/10.1117/12.366443
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