Description: Over the past decade, the importance of understanding the sources and sinks of carbon dioxide and othergreenhouse gases has been recognized. A variety of research studies funded by NASA, DOE and NOAA tomeasure the fluxes of CO2 from average conditions have been performed. In particular, flux measurements of CO2 in the boundary layer are critical toward understanding the carbon budget for this important greenhouse gas. The World Meteorological Organization has met its goal of 0.1 ppm CO2 accuracy for land based field sensors with gas chromatography and nondispersive infrared instruments. However, these instruments are poorly suited for small aerial platforms because of their high power requirements, large size and/or weight specifications. This proposal directly addresses NASA's need for high accuracy, small aerial platform, CO2 instrumentation for their Sierra and Dragon Eye UAVs, other unmanned aircraft such as launched and tethered balloons, and remote, unattended ground platforms where low power, compactness and self calibration are important. This instruments fits in with NASA's Technology Roadmap for satellite validation under the ASCENDS program and the OCO2 mission, as well as independent high resolution, nonintegrated CO2 profiles.To address this instrumentation need, Southwest Sciences has developed a compact (< 1 L), low power (< 2 watts), light weight (<1kg) diode laser based instrument to measure dry air corrected CO2 concentrations. Phase I was successfully completed. We achieved the Phase III targets in Phase I with a drift accuracy of <1 ppm at >1 hr and short term precision of 0.2 ppm at 1 second under static conditions. Over a 300 torr pressure range, 12°C temperature range, and 1.6% water addition, the system successfully measured within a standard deviationof 0.7, 0.8 and 0.4 ppm respectively of the actual concentration. The source of deviation was well characterized in Phase I and can be further reduced in Phase II.

Benefits: High accuracy, dry air corrected CO2 instruments for UAVs and manned aircraft would bridge the gap between current land based and satellite platforms. NASA would have new tools for making high accuracy mixing ratio measurements where manned airborne observations are risky (i.e. North Slope of Alaska) or for manned flights to replace current commercial instruments that are not meeting NASA's requirements with respect to speed, precision, and/or accuracy.

A direct commercial application of this project is the sale of research and environmental monitoring instrumentation to academic researchers, government agencies for large research and monitoring programs, and commercial entities for regulatory compliance applications. Although this proposal initially targeted UAVs and can be extended to manned aircraft, it can be further adapted as a rack mount and even as a hand held ultra portable instrument. Broader commercial application areas for this sensor include gas leak sensing for pipeline and carbon sequestration sites, fire detectors for commercial and private aircraft, combustor feedback control sensors, and process control sensors for energy and chemical production industries.