Room-Temperature Diode Laser Monitors for Spacecraft Air Quality/Air Revitalization Control

Advanced environmental monitoring and control technologies are required for future human exploration of the solar system, where the spacecraft air supply must be recycled for continuous use over a period of months to years. Primary target compounds and 180-day Spacecraft Maximum Acceptable Concentration (SMAC's) limits have been identified for several classes of contaminants. For the identified major species, O₂, CO, CO₂ and CH₄, room-temperature, near-IR tunable diode laser absorption sensors have already been demonstrated with ∼1 ppm-meter detection limits (at or below many of the current SMAC limits) and continuous response band widths on the order of 1 Hz. Additional sensitivity can be achieved using compact long pathlength multipass optical cells. These new generation diode laser sensors use communications-type diode lasers in compact, fiber-coupled packages ideal for remote and autonomous sensor applications. In this paper we will describe extensions of these diode laser sensor concepts for sensitive monitoring of a second class of contaminants, trace volatile hydrocarbons species. We will also describe results from a technology insertion demonstration of selected species detection at the NASA Johnson human habitat simulation.