Analysis Of The Influence Of Parameter Uncertainty On Calibration Accuracy Of Infrared Hyperspectral Interferometer

Infrared hyperspectral interferometer has become an important instrument for space borne atmosphere detection because of its advantages of multi-channel and large flux.Because of the complex structure,the calibration accuracy of the infrared hyperspectral interferometer is affected by the uncertainty of many calibration parameters,and some calibration parameters change slowly with time,so it needs to be updated irregularly.However,there are many kinds of uncertainties in on-orbit observation.At the same time,the uncertainty of some calibration parameters has similar influence on the calibration accuracy.Therefore,how to calculate the reasonable calibration parameters from on-orbit observation has always been the key and difficult problem in the field of on-orbit instrument calibration.In this paper,a method is developed which can simultaneously and quantitatively separate the offset of calibration parameters from the coupling calibration error.It can optimize the calibration parameters and improve the calibration accuracy.In this paper,taking the infrared hyperspectral atmospheric detector of FY-3D HIRAS as an example,the observation and calibration simulation model of the infrared hyperspectral interferometer is established.In order to accurately and quantitatively analyze the influence of the changes of instrument parameters on calibration results,based on the simulation model,the differential evolution model of calibration radiation on various calibration parameters is theoretically derived,and the sensitivity analysis of probe parameters,nonlinear coefficients and calibration source parameters is carried out respectively.The forward modeling and Jacobian matrix model of variational optimization are established.Finally,according to the deviation between the observed calibration radiation and the ideal(reference)radiation,the Variational-based Calibration Parameters Optimization Algorithm for Hyperspectral Infrared Sounder(Var Cal POA-HIS)is developed innovatively,and verified by the ground vacuum test and on-orbit data of FY-3D HIRAS.The main conclusions of this paper are as follows:1)Sensitivity analysis:for spectral calibration,the spectral wavenumber offset caused by 3?uncertainty of probe off-axis distance(444?rad)is about10ppm,while the spectral wavenumber offset caused by 3?uncertainty of probe radius(194?rad)is 1.8ppm,that is to say,the uncertainty of probe off-axis distance is the main factor affecting the spectral calibration accuracy;for radiometric calibration,the main parameter that affects the long wave band is inner blackbody temperature.The calibration brightness temperature deviation caused by its 3?uncertainty(0.06K)is 0.06K;The main parameter that affects the middle wave band is nonlinear coefficient.The calibration brightness temperature deviation caused by its 3?uncertainty(0.0384V^-1)is about 0.2-0.5K;The main parameter that affects the short wave band is cold screen emissivity,the calibration brightness temperature deviation caused by its 3?uncertainty(0.0009)shows very strong spectral characteristics,that is,in the strong absorption band,the deviation is as high as 0.6K,while in the window region,the deviation is within 0.02K.2)The application of Var Cal POA-HIS in coupled instrument error analysis on the simulation data:the optimal values of three sensitive calibration parameters(inner blackbody temperature,nonlinear coefficient and cold screen emissivity)are obtained by Var Cal POA-HIS,which are consistent with the given ideal values,and the accuracy can reach about 10^-4.For the target with the temperature of 290K,in the long wave,medium wave and short wave band,the calibration accuracy corresponding to the optimal calibration parameters is improved by about 0.1K,0.2-0.5K and 0.05-0.5K respectively.3)The application of Var Cal POA-HIS in coupled instrument error analysis on vacuum data and on-orbit data of HIRAS:for the vacuum test data,the test blackbody radiation with known temperature is taken as the reference radiation,for the on-orbit data,the on-orbit observation of Cr IS near the coincident orbit is taken as the reference radiation.The optimal value of calibration parameters is obtained by Var Cal POA-HIS,and the optimal value of calibration parameters is tested by independent samples.The verification results of vacuum test data show that for the targets with temperatures of 260.15-325.15K,the calibration accuracy of the optimal calibration parameters is improved averagely by about 0.3K,0.3K and 0.4K in the long wave,medium wave and short wave band,respectively,compared with the corresponding calibration accuracy of vacuum test values.The verification results of on-orbit data show that for the targets with different temperatures,the calibration accuracy of the optimal calibration parameters is improved averagely by about 1.4K,0.8K and 2.6K in long wave,medium wave and short wave,respectively,compared with that of the vacuum test values.The verification of on-orbit data in different seasons shows that the calibration accuracy corresponding to the optimal calibration parameters is stable,which proves the multi season applicability of the optimal calibration parameters and the stability of on-orbit performance of FY-3D HIRAS.In this paper,the feasibility of Var Cal POA-HIS in separating coupling instrument error is discussed from three aspects of simulation data,vacuumon data and on-orbit data.A feasible method of on-orbit monitoring of infrared hyperspectral instrument performance is provided,so as to improve the radiometric calibration accuracy of infrared hyperspectral data and better serve for numerical weather prediction.This work can further expand the research on the influence of calibration parameter uncertainty on the accuracy of inversion products,establish the demonstration relationship between satellite product accuracy and instrument parameters,and lay a good theoretical foundation for the demonstration of satellite and instrument indicators in the future.The research results in the simulation model,sensitivity analysis of calibration parameters and precise derivation of calibration parameters can also be applied to the engineering construction and instrument development process of infrared benchmark load in the future.It also has a very valuable reference for the error analysis and data accuracy improvement of other space borne instruments.