Advancements in the 2-μm Triple-Pulse Integrated Path Differential Absorption Airborne Lidar for Simultaneous CO2 and H2O measurements

Water vapor (H2O) and carbon dioxide (CO2) are the most dominant greenhouse gases directly contributing to the Earth's radiation budget and global warming. A new 2-mm triple-pulse Integrated Path Differential Absorption (IPDA) lidar for simultaneously measuring lower tropospheric weighted-column average dry-air volume-mixing ratios of H2O and CO2 is currently under development at NASA Langley Research Center (LaRC). The IPDA transmitter generates three consecutive pulses at three different wavelengths separated by approximately 200 ms, for each pump pulse at 50 Hz pulse repetition rate. Wavelength tuning and locking for each of the generated pulses are optimized to achieve independent H2O and CO2 measurements with minimum interference from either of the two gases. The IPDA receiver includes two direct detection systems based on different detection technologies. The first detection system is based on InGaAs pin detector, previously demonstrated in the 2-mm double-pulse IPDA lidar. The second detection system is based on HgCdTe (MCT) electron initiated avalanche photodiode (e-APD) that was demonstrated in 1.6-mm lidar. Advancements of the triple-pulse IPDA lidar component development and testing and system integration will be presented. These components include laser transmitter and timing control electronics, wavelength center-line locking and side wavelength generation, MCT detection system and digitizers. Ground-based testing of these components is being conducted using the 2-mm double-pulse IPDA lidar instrument in a lidar mobile laboratory located at NASA LaRC. This setup allows evaluation of technology developments, system operation and testing of software and data retrieval algorithms. The facility at LaRC includes calibrated hard targets for horizontal ranging up to 1 km, ground-based meteorological observation site (CAPABLE) and a CO2 and H2O in-situ sensor (LiCor). The development and testing of the new lidar technologies are critical for aircraft deployment and enabling for future space-based CO2 column measurement systems.