Laser Sounder for Active Remote Sensing Measurements of CO2 Concentrations

We report on progress of our CO₂ laser sounder laboratory breadboard system the goal of which is to measure the integrated column abundance of CO₂ to better than 1 ppm from low Earth orbit globally, measuring at all latitudes and seasons through day and night. The challenge for an orbiting CO₂ instrument is to achieve high precision not high sensitivity. We have made simple yet significant improvements to our active, optical-sensing laser-sounder instrument and real-time data processing that now enables absolute absorption measurements to better than plusmn 0.05% for over 10 hours before re-calibration (equivalent to a 1 ppm precision from orbit). Data from an eight day, 0.8 Km open path comparison test with a LICOR shows excellent agreement.