| Global calibration site network plan has been carried out to meet the high-frequency on-orbit radiometric calibration requirements of the diversified,differentiated and complicated satellite remote sensors,and to better track the changes in the on-orbit radiometric characteristics of remote sensors.That is to say,by selecting sites which are suitable for the on-orbit radiometric calibration to organize a calibration network globally,and jointly using the reflection/emission characteristics of multiple sites,high-frequency calibration of remote sensors can be performed.There is an urgent need for reflectance data that can accurately describe the characteristics of these sites for high-frequency on-orbit calibration.With the application of high-resolution,hyperspectral and multi-angle remote sensors,the acquisition of reflectance data from a single data source cannot meet the temperal,spacial and spectral requirements of global calibration field reflectance data.Combined with the technical requirements for high-frequency on-orbit calibration of satellite remote sensors,this thesis carried out research on the acquisition,fusion and high-frequency on-orbit calibration application of multi-source reflectance data.A global multi-site calibration data acquisition and fusion technology scheme is proposed,and a data conversion algorithm of time,space and spectra dimension is designed.The missing data filling of MODIS,the conversion of multi-scale image and the spectral fiision of Landsat’s high spatial resolution image and Hyperion’s high spectral resolution image Hyperion is realized,and the reflectance data of 57 global calibration fields are generated.It provides basic data support for the realization of high-frequency on-orbit calibration supported by multi-source remote sensing data.Based on the measured data,a hyperspectral BRDF model of Dunhuang radiometric calibration test site was constructed,and Landsat-8/OLI and SNPP/VIIRS were used to achieve the on-orbit radiometric calibration using the site BRDF model.6 effective calibrations have been completed by using the transit image of Landsat-8/OLI from July to September 2018,and 51 effective calibrations have been completed by using the transit image of SNPP/VIIRS transit images in 2018.The calibration frequency has been increased from 1-2 times a year to 2-4 times a month,significantly improving the calibration frequency of the remote sensors.Using the multi-source surface reflectance data set of 57 calibration sites and combined with the BRDF model supported by MODIS data products,the on-orbit radiometric calibration of DPC,the first full polarization satellite remote sensor with wide field of view in China was carried out,and the influence in the results of DPC’s different flight angles and the sun-satellite relative azimuth was analyzed.From May 2018 to January 2019,a total of 36 sites were used to complete more than 137 effective calibrations in 6 bands,and the dynamic range of the site reflectance was between 0.042 and 0.962.The calibration results show that the wide dynamic range,long time series and high-frequency on-orbit radiometric calibration of the remote sensors can be realized by using the global calibration field reflectance data. |
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