Research On High Resolution Radiation Calibration Method

The radiation calibration of the satellite sensor is to ensure the accuracy of the remote sensing image data acquired by the sensor,and its calibration accuracy determines the product quality of the quantitative remote sensing satellite.In order to be able to track the changes of the sensor's radiation characteristics in time,site calibration has been carried out at home and abroad.Site calibration requires measuring real-time data of the calibration site during satellite transit.The manpower,material and financial resources consumed cannot meet the highfrequency calibration requirements of domestic high-resolution satellites.The thesis uses the characteristics of high-resolution satellite camera to study the high-resolution satellite radiation calibration method.The specific research content includes the following aspects:(1)For the imaging characteristics of Gaofen-6(GF6)satellite,this paper analyzes the surface characteristics of multiple domestic calibration sites and solves the defect of using the Dunhuang radiation calibration site as a single calibration site.After data preprocessing and calculation Get the gain and offset of GF6.Taking the site calibration data published by China Resources Satellite Application Center as the evaluation basis,the calculated absolute radiation calibration uncertainty is within 4.5%,which meets the accuracy requirements for the production of remote sensing radiance products and the calibration accuracy of multi-site radiation calibration can be improved as a reference for the subsequent time series calibration method.(2)For the image formed by the intersection of the instantaneous position of the satellite camera and the line of the center of the earth at the surface of the earth,the atmospheric correction radiation transmission model MODTRAN4 and the satellite side-swing angle correction method are used,and the cross radiation calibration method is used to calculate the gain coefficient.The results show that the uncertainty of radiation calibration after atmospheric correction method has been reduced.In order to eliminate the chance of single calibration,31 sets of images of Gaofen1(GF1)multi-spectral wide-field imager(WFV4)are selected to carry out radiation calibration in sequence.The radiation calibration method after atmospheric correction and satellite side-swing angle correction can reduce the errors caused by different observation angles.(3)Utilizing three domestic radiation calibration fields,combined with data products of medium resolution spectral imager(MODIS),data products,select 2013-2019 GF1/WFV4 146 effective matching images,using the solar altitude angle correction technology and batch processing algorithm to complete the time series calibration of the GF1/WFV4 camera,the results show that the time series calibration coefficient of the GF1/WFV4 camera is in good agreement with the official calibration coefficient The radiation performance of the GF1/WFV4 camera was stable in 2013-2017.During 2017-2019,the 1,2,and 3 bands showed an upward trend,and the 4 band showed a downward trend.The time series calibration results are used to achieve continuous monitoring of the satellite load on-orbit radiation characteristics,and provide a reference for scientific researchers to correct the satellite load calibration coefficients in time.