A broad band lidar for precise atmospheric CO2 column absorption measurement from space

Accurate global measurement of carbon dioxide column with the aim of discovering and quantifying unknown sources and sinks has been a high priority for the last decade. In order to uncover the “missing sink” that is responsible for the large discrepancies in the budget the critical precision for a measurement from space needs to be on the order of 1ppm. To better understand the CO₂ budget and to evaluate its impact on global warming the National Research Council (NRC) in its recent decadal survey report (NACP) to NASA recommended a laser based total CO₂ mapping mission in the near future. That´s the goal of Active Sensing of CO₂ Emissions over Nights, Days, and Seasons (ASCENDS) mission-to significantly enhance the understanding of the role of CO₂ in the global carbon cycle. Our current goal is to develop an ultra precise, inexpensive new lidar system for column measurements of CO₂ changes in the lower atmosphere that uses a Fabry-Perot interferometer based system as the detector portion of the instrument and replaces the narrow band laser commonly used in lidars with a high power broadband source. This approach reduces the number of individual lasers used in the system and considerably reduces the risk of failure. It also tremendously reduces the requirement for wavelength stability in the source putting this responsibility instead on the Fabry-Perot subsystem.