Title: Test Results for the Broad Band Carbon Dioxide Lidar
Author: William Heaps
Organization: NASA Goddard Space Flight Center
Co-Authors: Elena Georgieva, Wen Huang

There is a great need for measurements of atmospheric carbon dioxide concentration with high spatial and temporal resolution for global and regional studies of the carbon cycle. Such measurements will better resolve the linkage between global warming and anthropogenic CO2 emissions. In the Decadal Survey of Earth Science the National Research Council recommended that NASA develop, build, and fly a laser based system for precision measurement of total carbon dioxide column (the ASCENDS mission). The mission demands measurements of CO2 to a precision of 1 ppm out of the total ~400 ppm column in order to locate sources and sinks. Achieving this 400:1 precision is made more difficult due to the strong dependence on changes in atmospheric pressure and temperature of atmospheric carbon dioxide absorption line position, shape, and strength. Most lidar systems currently under development as candidates for the ASCENDS mission require multiple lasers operating at different, very narrow bandwidth wavelengths in order to resolve these effects. NASA has never flown a narrow band wavelength controlled laser in space. Our team at Goddard Space Flight Center (GSFC) is developing a lidar system for column CO2 measurement based on an innovative new lidar technique employing a spectrally broad laser source and using a Fabry-Perot based detector. Our lidar is capable of mitigating inaccuracy associated with atmospherically induced variations in CO2 absorption line shape and strength while reducing the number of individual different wavelength lasers required from three or more to only one. It also reduces the requirement for source wavelength stability, instead putting this responsibility on the Fabry-Perot based receiver. This system is scheduled to participate in flight testing from NASAís DC-8 aircraft in early April of 2011.This presentation will present results of ground based plus airborne testing of this innovative new system and discuss its potential application as a space borne sensor for the ASCENDS mission.