Room-Temperature Diode Laser Monitors for Spacecraft Air Quality

Room-temperature, tunable diode lasers operating in the visible and near-IR spectral region have been shown to meet detection sensitivity and time response requirements for most major species and rapid-response pyrolysis product measurements identified for spacecraft environmental monitoring applications. Multi-laser sensors with multiplexed fiber-delivery systems appear to be feasible for simultaneous monitoring of several individual contaminants. Work is underway to extend this approach to a number of volatile organic compounds using overtone and combination band absorption in the 1.5 to 2.0 μm wavelength region. The first quantitative measurements of these absorption bands have been obtained in pure vapors using a sensitive, near-IR FTIR spectrometer. These results are being used to guide the selection of custom-fabricated diode lasers for sensitive and rapid detection of trace contaminant levels.