Calibration And Analysis Of The Radiation Performance Of The Gaofen-6 Satellite

GF-6 satellite is an extremely important satellite in China’s high-resolution earth observation system.It has the advantages of high spatial resolution,wide coverage and high localization rate.Since its launch in 2018,it has provided a large quantity of remote sensing image data support for rural planning,natural disaster prediction,and land management and supervision.The quality and accuracy of quantitative remote sensing are determined by radiometric performance,so in this study,the SNR(signal-to-noise ratio)and DR(dynamic range)are selected to evaluate the radiometric performance of GF-6 satellite calibration.Because the stability analysis of satellite radiometric performance cannot be carried out in a single site,the cross radiometric calibration based on multi site is carried out,and the time series calibration is constructed to analyze its radiation stability.The specific research contents are as follows.(1)Putting forward the radiation quality evaluation of GF-6/WFV sensor,the satellite image radiation quality of GF-6 / WFV is evaluated by using SNR and DR.SNR can effectively reflect the overall light and shade of each wave band and distribute the energy of the ground objects with different radiance.DR can compare the ability of sensors to distinguish the subtle changes of the radiation energy of the ground objects.The results show that the SNR of the GF-6/WFV image is larger than the 28 d B designed by satellite,which indicates that it has better SNR.The DR of GF-6 / WFV image is smaller than that of Terra / MODIS image.Combined with the quantitative values of the two images,it shows that the radiometric performance of GF-6/WFV image has a certain gap compared with the satellite sensor with high radiometric performance.(2)According to the characteristics of GF-6/WFV sensor,this paper uses Terra/MODIS and Landsat 8/OLI sensors to do cross radiometric calibration research on it.The results show that the uncertainty of GF-6/WFV sensor cross radiometric calibration is within 6%,which indicates that the method of cross radiometric calibration is accurate and credible.On this basis,this paper selects radiometric calibration sites with different responses to carry out cross radiometric calibration research.The results show that the uncertainty of calibration coefficients obtained by multi site cross radiometric calibration is within 5%,which improves the accuracy of single site cross radiometric calibration.(3)In view of the lack of site calibration of GF-6 satellite and the inability to effectively analyze the stability of radiometric calibration,GF-6/WFV and Terra/MODIS sensors were used for time series calibration research.According to research findings,it was the in-orbit test period of the satellite in 2018,with less satellite data.The uncertainty of the calibration coefficient was biggish,and the jitters of the satellite’s radiation performance occurred after a half-year inorbit test period.In the period of 2019-2020,the satellite radiation performance tended to be stable,and the calibration uncertainty was about 5%.The radiometric performance of GF-6/WFV sensor changed little during this period,which could meet the operational requirements of quantitative remote sensing.