Simulation And Inversion Of Spatial Heterodyne Interferometric Hyperspectral Temperature Detection From O₂ A-Band Night Glow In Mesosphere And Lower Thermosphere

The Mesosphere and Lower Thermosphere（MLT）refers to the atmospheric region with altitudes ranging between 80 and 120 km.As Earth’s climate models expand to higher altitudes,the MLT plays an increasingly important role in the establishment of climate models,prediction,and forecasting.Within the MLT,temperature stands as a crucial state parameter that exerts substantial influence on atmospheric photochemical processes,energy balance and momentum balance.Therefore,the study of temperature distribution aids in human comprehension of intricate atmospheric phenomena.By utilizing hyperspectral remote sensing data of O₂ A-band night glow（b¹∑_g⁺-X³∑_g^-,762 nm）,it is possible to retrieve MLT temperature,and spatial heterodyne interferometric spectroscopy offers a potential approach for hyperspectral spaceborne detection of the tracer.To retrieve the temperature and ensure inversion accuracy,it becomes necessary to construct a detection simulation system based on spatial heterodyne interferometric spectroscopy for enhancing and optimizing inversion models using the obtained hyperspectral data.Consequently,this article focuses on simulating high-resolution,temporally capable,and hyperspectral detection systems based on spaceborne spatial heterodyne technology along with corresponding inversion algorithms.This paper supplements existing photochemical models based on the O₂ A-band night glow emission mechanism,optimizes O2 related molecular spectral data.By incorporating atmospheric radiative transfer theory in limb mode,a forward model is developed to simulate the radiative spectra within the MLT region of the target airglow.Leveraging Odin-OSIRIS’ in-orbit observation conditions as input parameters,the simulated spectra are convolved with OSIRIS Instrument Line Shapes（ILS）and subsequently compared to actual observational data to analyze discrepancies and provide an initial validation of the accuracy of forward model.Furthermore,utilizing the simulation results of the forward,we optimize main performance parameters of a spaceborne spatial heterodyne interferometric system,including detection band and spectral resolution,and generate simulated observation data of the target emissions.The MLT temperature inversion algorithm was conducted using recovering spectra.The optimal estimation,least squares,and peak relative intensity ratio method were studied and compared,resulting in the acquisition of MLT temperature profiles.A nonlinear iterative inversion method based on optimization theory was optimized with the constraints of Tikhonov regularization matrices.This optimization was incorporated into the optimal estimation,resulting in an improvement of approximately 0.4 K in temperature inversion accuracy.Furthermore,the study investigated the impact of a priori constraints on inversion accuracy.The results demonstrated that by controlling a priori profile accuracy within ±5 K,the average accuracy of temperature profiles could surpass 1.4 K within the MLT region with a vertical resolution better than 2 km.This paper quantitatively assesses the factors that influence the uncertainty of inversion results.The primary emphasis is on investigating the impact of SHS parameters,such as detector bad pixels,spectral resolution,spectral and radiometric calibration accuracy,and detection timeliness on temperature sensing accuracy.The results are as follows:（1）The selected detector bad pixels with rate of 1‰ only result in an accuracy loss of less than 0.1 K in temperature inversion.（2）Decreasing the spectral resolution from 0.8 cm^-1 to 12.5 cm^-1,with coarser a priori constraints,leads to an average decrease of approximately 1.2 K in temperature retrieval accuracy.With optimized a priori constraints and a spectral resolution of 0.8 cm^-1,the average inversion accuracy reache1 ±2 K.（3）When the spectral calibration uncertainty is 0.1 cm^-1,the temperature inversion accuracy decreases by approximately 1.0 K.When the radiative calibration uncertainty is at 1%,the temperature inversion accuracy decreases by around 0.6 K.The combination of atmospheric profile simultaneous split-field-ofview imaging technology and spatial heterodyne spectroscopy enhances timeliness in temperature detection,enabling capturing of gravity wave-induced temperature perturbations and ultimately reducing detection errors.Lastly,the paper conducted global-scale MLT temperature inversions to obtain spatiotemporal distribution characteristics of temperature and inversion accuracy.The average global inversion accuracy is approximately ±2 K,with an even better average accuracy at the Mesopause being less than 1.5 K.