Reliability Demonstrating Of Space-borne Greenhouse Gases Measurement Using IPDA Lidar

Carbon dioxide(CO2)is a long-time atmospheric component which is considered as one of the most important greenhouse gases sustainably increasing since industrial revolution.The analysis of the trend of carbon dioxide concentration is important for studying the interaction of carbon dioxide source and sink,understanding climate change and controlling carbon dioxide emission.Obtaining high precision carbon dioxide data from global scale is helpful to the analysis of carbon flux in the model study,understanding the source and sink distribution mechanism and promoting the study of the relationship between carbon dioxide and climate.The data of carbon dioxide column with accuracy better than 1 ppm can meet the requirement of most models for carbon dioxide data which is very strict for the actual measurements.Spaceborne integrated path differential absorption lidar(IPDA)which designed as a new generation of global carbon dioxide content detection tool can achieve day and night detection,global-coverage measurement,and the laser pulse weighting on the lower atmosphere and the inversion data expressed as the dry-air column weight of carbon dioxide(XCO2).XCO2 with high precision and high spatial resolution,will meet the precision requirements of carbon dioxide model research.In this paper,the error analysis of various parts of space-borne IPDA lidar detection is carried out,including the optimization of spectral line pulse wavelength,the analysis of the transmitting unit,the receiving unit and the load part of the lidar system,and the influence of the atmosphere profile and the surface reflectance in the transmission process of the pulses.In the papser,the main contents include following aspects:1.Optimizing the laser pulse wavelength of the system.The weighting of pulse is not lonely focus on the lower atmosphere,but also the detection is less affected by the CO2 fluctuation near the ground.The abtained data is closer to the actual atmospheric CO2 concentration.2.The influence of the parameters and load parameters of the lidar system are analyzed.The instability of pulse energy linewidth,pulse energy accuracy and laser pulse frequency in the transmitting unit of the system are analyzed,and the influence of spectral purity and Doppler frequency shift on the detection is discussed.3.In the study of receiving system,the influence of the interference from shot noise,background radiation and speckle noise are studied,and the influence of telescope and APD detector on the detection are analyzed.In the load part,the selection of spatial resolution,orbital height and other auxiliary parameters are analyzed.4.The influence of the parameters on the detection of CO2 in the atmospheric transmission and the surface reflection process are analyzed.An optimal analysis algorithm for airborne IPDA detection is presented.The influence of the atmospheric path length and the gravity constant is discussed,in which the length of the atmospheric path includes the atmospheric delay and the distance from the satellite to the surface using the Digital Elevation Model.This paper expounds the effect of cloud and aerosol on the detection,and puts forward the research ideas of using cloud surface reflection through statistical analysis and scene simulation.The influence of the surface reflectance on the detection is analyzed emphatically,because the difference of the reflectivity of the pulse wavelength in the surface footprint is one of the most important error sources,and the relative surface reflectance method can effectively reduce the error caused by the overlap of the surface footprints.At last,a method for detecting atmospheric CO2 using the IPDA method of satellite-borne retroreflector is presented.Finally,according to the analysis of the detection error of each part,the detection error and the error distribution are given,and the error analysis results meet the requirements of the detection accuracy of CO2 and the requirements of the system.According to the error analysis,the paper analyzes the error distribution scheme,considers the overall requirements of the instrument and provides the theoretical basis for the performance optimization and improvement of the instrument.It provides the basis for the error analysis and product research of the measured data in the future.