Sensitivity analysis and correction algorithms for atmospheric CO2measurements with 157-µm airborne double-pulse IPDA LIDAR

. Moreover, the systematic errors caused by the laser pulse energy, linewidth, spectral purity, and frequency drift, as well as the atmospheric parameters related to the flight experiments are also investigated. The relative system error (RSE) was 0.214% as determined based on an analysis of the systematic errors, which are primarily caused by the frequency drift. Two methods are proposed to reduce the RSE caused by the frequency drift. The first is the averaging of 148 shots, which can reduce the RSE to 0.096%. The other method involves calculating the integral weight function (IWF) using real-time frequency. However, this is a time-consuming and computationally intensive process. Hence, look-up tables for the absorption cross-section were created to overcome this issue, resulting in a decrease in the RSE to 0.096%. Using actual aircraft attitude angles, velocity, and position data from flight experiments, the relative errors (REs) in the IWF caused by the uncorrected integral path and Doppler shift were determined to be 0.273% and 0.479%, respectively. However, it was found that corrections to the integral path and Doppler shift based on accurate calculations of the IWF cause the airborne platform to turn in such a way that the REs are eliminated. Hence, this study confirms the validity of system parameters and provides a reference for other researchers who study similar IPDA LIDAR systems. Further, the sensitivity analysis of the airborne IPDA LIDAR system can provide a reference to future data inversions. Moreover, the proposed correction algorithms for the integral path and Doppler shift contribute to more accurate inversion results.