2-um Differential Absorption Lidar for Martian Atmospheric CO2 and atmospheric Pressure measurements

Martian atmosphere consists dominantly of CO₂ gas. Observations of atmospheric CO₂ amount would provide crucial knowledge on Martian CO₂ annual cycles, surface air pressure variations, and atmospheric dynamics including dust storms. This team explores a great potential to use a Martian differential absorption lidar (DIAL) operating at the 2-um CO₂ absorption band for the purpose. For the considered system, closely-spaced wavelengths are selected so that Martian environmental impacts such as surface reflection, atmospheric scattering, and absorption from other trace gases on the lidar return signals are very similar, but the difference in CO₂ absorption is substantial. The Martian CO₂ amount and surface air pressure could be retrieved from the measured CO₂ differential absorption optical depth at the selected wavelengths. Simulation studies found that return signals from the surface for a Martian space-borne CO₂ DIAL system could have sufficient signal strengths that allow column CO₂ amount and surface air pressure measurements with 1% and 1 Pa precision, respectively, after horizontally 5 km averaging under normal weather/dust conditions. These CO₂ and pressure measurements would significantly improve Martian weather and climate modeling and prediction. Current study of the Martian CO₂ DIAL system and laboratory experiments show that a 2-um CO₂ DIAL system for Martian atmospheric applications can be developed with existing fiber laser and lidar technologies. These results indicate that Martian space-borne CO₂ DIAL systems significantly improve next-generation Mars’ weather and climate predictions and greatly benefit future human Mars explorations. We report the latest progress in the lidar development including certain instrumentation and laboratory experimental results.