Study On Cross Calibration Method Of Jilin-1 Spectral Satellite Based On FY-3 Satellite

Due to the influence of on orbit space environment change,component circuit aging and other factors,the radiation performance of satellite sensors will continue to decay,which directly affects the quantitative product accuracy and application effect of satellite remote sensing data.The Jilin-1 Spectral Satellite has launched in January2019.At present,a large number of data have been obtained and widely used.However,due to its short launch time,there is no systematic research of on orbit radiometric calibration.Although other domestic satellite calibration methods have been mature,whether they can be applied to Jilin-1 Spectral Satellite still needs to be studied and discussed.If the traditional site calibration is adopted,the satellite ground synchronous measurement test needs to be carried out,which is greatly affected by the satellite orbit and atmosphere,the number of tests is limited and the cost is high.If the traditional cross calibration method is used for calibration,because the number of visible and near-infrared bands reaches 20,it is impossible to find a sensor that matches its bands one by one,so the traditional cross calibration method is not applicable.In order to explore how to carry out high-precision calibration of Jilin-1 Spectral Satellite,this paper studies the cross calibration method of Jilin-1 Spectral Satellite with FY-3D as the reference.Firstly,the site calibration accuracy of the reference satellite FY-3D is studied by site calibration method.In this paper,the apparent radiance of satellite image is obtained as the relative truth through the official calibration coefficient.Then,the spectrometer carried by the UAV is used to construct the site BRDF model.After correcting the ground synchronous measured reflectivity data by the model mentioned,the apparent radiance is fitted based on the radiative transfer equation as the calculated value.The accuracy of the reference satellite is studied by comparing the relative difference of the apparent radiance between the two methods.Secondly,the cross calibration method of Jilin-1 Spectral Satellite is studied.In this paper,the correlation between sensors is established based on the spectral response and band matching method.For the bands where the spectral response of the two satellite sensors cannot be "one-on-one" matched,two multi-band weighted fitting methods are constructed to calculate the calibrated apparent reflectivity after calibration,then calculate the calibration coefficient,and analyze the experimental results with the coefficient of variation as the relative difference.Finally,after completing the research of cross calibration method,the calibration coefficient is tested.Based on the cross calibration coefficient,this paper uses the historical reflectance calibration method based on stable target and the apparent reflectance obtained from landsat-8 satellite image to compare and test the accuracy.The research of this paper shows that:(1)FY-3D Satellite can be used as the reference satellite for calibration research.The absolute value of the average relative difference of apparent radiance in different bands fitted by site calibration and satellite image is 2.24%,and the band with the largest relative difference is 3.89%.The above results show that FY-3satellite operates stably in orbit without obvious attenuation,and its cross calibration accuracy as a reference satellite is high.At the same time,for such satellites with large zenith angle,the calibration accuracy can be improved after BRDF correction of ground reflectivity.(2)Through the cross calibration method,the high-precision calibration coefficient of Jilin-1 Spectral Satellite can be obtained.In this paper,through the Dunhuang radiometric calibration field and taking Feng Yun-3 satellite as the reference,seven images of Jilin-1 Spectral Satellite from2019 to 2021 are obtained for cross calibration.The results show that the relative difference of calibration coefficients of all bands in different time phases varies from2% to 6%,and the average relative difference is 3.92%,indicating that the calibration results of Jilin-1 Spectral Satellite on different dates have good consistency,that is,the cross calibration results are more reliable.At the same time,according to the historical reflectance data and Landsat-8 image,the high accuracy of the cross calibration method in this paper is verified by relative difference analysis.