Airborne Calibration Test Of CO₂ Concentration Detection Lidar And Research On Satellite-borne Inversion Algorith

Since the industrial revolution,due to a series of anthropogenic carbon emission activities such as the excessive combustion of fossil fuels and the change of land use type.The original carbon balance in the atmosphere has been broken,resulting in the continuous rise of CO₂ concentration in the atmosphere.Severely affecting the global climate and the environment that humans depend on for survival.Therefore,it is necessary to accurately monitor the column concentration of atmospheric CO₂ around the world,which is of great significance for studying the carbon cycle and predicting future climate change.In recent years,many countries have carried out research on passive remote sensing satellites for global CO₂ column concentration observation.However,passive remote sensing satellites can only be carried out under cloud-free and sunny conditions,and cannot achieve nighttime and high-latitude observation.Therefore,it is necessary to have a spaceborne active remote sensing equipment that can achieve all-day,high-precision and global observation of CO₂ column concentration.The spaceborne Integrated Path Differential Absorption（IPDA）lidar can achieve high-precision detection of global CO₂ column concentrations due to its unique working principle.However,the successful launch of spaceborne IPDA lidar has great technical and engineering challenges.Before the launch of the spaceborne IPDA lidar,the key technology of spaceborne IPDA lidar observation can be verified by carrying out the flight test of the airborne IPDA lidar,which is very similar to its observation method.In addition,a high-precision airborne IPDA lidar data inversion algorithm can be established through the airborne flight calibration test,laying the foundation for the data inversion algorithm of the spaceborne IPDA lidar.This paper focuses on the research of airborne flight calibration test and inversion algorithm based on spaceborne CO₂ column concentration detection lidar.The main research contents of this paper are as follows:1.Simulation analysis of airborne IPDA lidar system.It is necessary to carry out simulation analysis on its working performance before developing the airborne IPDA lidar system.Firstly,based on the working principle and system parameters of the airborne IPDA lidar,the original echo signal and the echo SNR distribution characteristics of the airborne IPDA lidar with different surface reflectivity and different aerosol optical depth are calculated.Secondly,the system error caused by the uncertainty of atmospheric parameter measurement and system parameter uncertainty is simulated,and the performance of the airborne IPDA lidar system is evaluated.2.An airborne IPDA lidar system is developed and ground verification experiments are carried out.After completing the simulation of the airborne IPDA lidar system,the first airborne IPDA lidar system in China was successfully developed.Before the airborne flight calibration test,the lidar system was used to carry out the ground horizontal observation experiment,and the observation results were compared with the measurement results of the ground greenhouse gas in-situ measuring instrument,which verified the working performance of the system.3.The first flight calibration test of airborne IPDA lidar in China was carried out and a high-precision data inversion algorithm for airborne IPDA lidar was established.The flight calibration test passes through a variety of surface types.The ground observation stations are arranged on the flight path,and the distribution characteristics of CO₂ column concentration under different surface types are detected through the air-ground joint observation method.The matching filtering algorithm and pulse integration algorithm are used to optimize the traditional IPDA lidar data inversion algorithm,and a set of high-precision airborne IPDA lidar data inversion algorithm is established.By comparing the observation results of the airborne IPDA lidar with the measurement results of the passive satellite and the calculation results of the CO₂ model,the reliability of the optimized airborne IPDA lidar data retrieval algorithm is verified.4.The inversion algorithm for spaceborne IPDA lidar data is established and the inversion verification is carried out on the observation data of DQ-1 satellite IPDA lidar.Comparing the similarities and differences of the observation methods of the airborne IPDA lidar and the spaceborne IPDA lidar,a set of data inversion algorithms suitable for the spaceborne IPDA lidar is established on the basis of the data inversion algorithm of the airborne IPDA lidar.The data of DQ-1 satellite IPDA lidar in June 2022 were retrieved using the established satellite data retrieval algorithm.The retrieval results were compared with the observation data of OCO-2（Orbiting Carbon Observatory-2）passive satellite and ground TCCON（Total Carbon Column Observing Network）station,which verified the working performance of the satellite IPDA lidar and the reliability of the satellite IPDA lidar data retrieval algorithm.