Compact CO2 Instrumentation for Small Aerial Platforms

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. More »