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The progress in the development of a sensor for the detection of trace air constituents to monitor spacecraft air quality is reported. A continuous wave, external-cavity tunable diode laser centered at 1.55 μm is used to pump an optical cavity absorption cell in cw-Cavity Ringdown Spectroscopy (cw-CRDS). This technique exploits the sensitivity enhancements provided by the long effective pathlength from the optical cavity created between two highly reflective mirrors (R>0.9999). Preliminary results are presented that demonstrate the sensitivity, selectivity, and reproducibility of this method. Detection limits of 2.0 ppm for CO, 2.5 ppm for CO2, 1.8 ppm for H2O, 19.4 ppb for NH3, 7.9 ppb for HCN, and 4.0 ppb for C2H2 are calculated.

The progress on the development of a sensor for monitoring spacecraft air quality is reported. A 1.55 μm external-cavity tunable diode laser is used as a light source that can be incorporated in either cw-Integrated Cavity Output Spectroscopy (cw-ICOS) or cw-Cavity Ringdown Spectroscopy (cw-CRDS). Both techniques exploit the sensitivity enhancements provided by the long effective pathlength from the optical cavity created between two mirrors. Initial experiments of cw-ICOS have been performed to determine the sensitivity, selectivity, and reproducibility of this method. Passing the laser beam through a flame supported on an atomic absorption burner produced a dense spectrum of absorption lines in the 1545–1560 nm region. While most of the absorbance peaks observed in the flame were assigned to water, a number of spectral features have been assigned to the OH radical.

An optical sensor for the detection of carbon dioxide concentrations and stable isotope ratios is described. Either a continuous wave, fiber-coupled distributed feedback laser or an external cavity laser is used to pump an optical cavity absorption cell in cw-Cavity Ringdown Spectroscopy (cw-CRDS). This technique exploits the sensitivity enhancements provided by the long effective pathlength from the optical cavity created between two highly reflective mirrors (R>0.9999). The inherently high precision of the technique combined with its rapid data throughput allows for reliable measurements of both concentration and the isotopic composition of the sampled carbon dioxide. Data collected using a prototype of this sensor could be useful for monitoring module occupancy, crew health (through breath tests), and plant growth chambers.