Research On Automatic Calibration Of Meteorological Remote Sensing Satellite Payload

At present,meteorological satellites play a more and more important role in daily life.People have higher and higher requirements for the accuracy of satellite observation.With the increasing number of meteorological satellites launched in recent years,the simpleness and sustainability of radiation stamps of satellite venue have also proposed higher requirements.The traditional manual observation and single or several observation can not meet the needs of satellite remote sensor in orbit calibration and remote sensing data quantitative application,so it is urgent to push the observation of ground surface and atmospheric optical band radiation characteristics to the stage of automatic and continuous observation.Under this background,this paper takes the Dunhuang satellite radiometric calibration field as the experimental site,and studies the automatic observation equipment and calibration process in detail.The main research contents include the following aspects:(1)In this paper,the surface radiation characteristics of Dunhuang satellite radiometric calibration site are analyzed in detail from the aspects of time stability and spatial homogeneity by using the surface measured data obtained during the two Fengyun satellite authenticity verification experiments in spring and summer and autumn of 2018.It further verifies the advantages of Dunhuang site calibration,and provides a theoretical basis for the conversion of multispectral surface reflectance observed by site radiometer to hyperspectral surface reflectance in automatic calibration.The BRDF reflectivity correction which affects the calibration results is studied.The calibration error is effectively reduced by using the corrected nuclear coefficient for radiometric calibration calculation.(2)The automatic observation equipment was used to calibrate the Fengyun meteorological satellite for many times,and the deviation of the calibration results was compared and analyzed in the same period.The comparison results show that: in spring,except for the bands greatly affected by water vapor,the overall relative deviation of manual calibration is less than that of automatic calibration,but in individual bands(such as band 14,15),the automatic calibration is better than the manual data.In summer and autumn,the results of manual calibration and automatic calibration are almost the same.In a word,compared with manual calibration,automatic calibration can ensure the high frequency of calibration while the accuracy is equivalent.In addition,it is found that the fluctuation of the results of manual calibration is greater than that of automatic calibration in the stability of observation data.From the water vapor influence band,it can be seen that due to the automatic judgment of sky cloud cover and weather by automatic instruments,the fluctuation of the data obtained by automatic calibration is significantly improved compared with that of manual data.(3)The radiometric calibration system software of Dunhuang site automatic observation is developed to generate the surface and atmospheric data products of site automatic observation,and realize the satellite radiometric calibration processing based on site automatic observation data.The software interface of Dunhuang site automatic observation radiometric calibration system is simple and easy to use.The user can select the satellite to be calibrated and input the required atmospheric parameters and geometric parameters to obtain the observed DN value of the calibration satellite and the surface retrieved apparent reflectance,thus completing the whole calibration process.(4)Based on the internationally recognized cross calibration standard instrument MODIS,the automatic calibration accuracy is verified,and the factors causing calibration error in the process of automatic calibration are analyzed in detail.The sources of measurement errors of surface reflectance,aerosol optical thickness,BRDF and radiative transfer model and the variation of final inversion uncertainty caused by each calculation process are discussed.The results show that the average overall deviation of manual calibration is less than 2%,and the average deviation of automatic calibration based on reflectance based method is slightly larger than 3.23%.In addition,several main factors causing the uncertainty of calibration,such as surface reflectance,atmospheric parameters,radiative transfer model,are analyzed in detail,and the overall uncertainty of automatic calibration in this paper is determined to be between5.17% and 6.47%.Based on the instruments and equipment with automatic and long-term field work ability deployed in the field observation base of Dunhuang station of China National Satellite radiometric calibration field,this paper introduces the automatic operational observation ability of surface measurement equipment and atmospheric parameters of the automatic observation base in detail,studies the automatic calibration process,analyzes the calibration accuracy and uncertainty,and provides reference for Fengyun meteorological station It lays a theoretical foundation for operational radiometric calibration of satellites and related transit satellites at home and abroad.