In recent years, high spatial resolution remote sensing observations collected by various sensors have become widely used for environment, vegetation and land-use monitoring, etc. However, it is very important to convert the observations from different sensors to a same scale by absolute radiometric calibration that is traceable to SI. This study introduces a radiometric benchmark transfer calibration approach for the space-borne solar reflective bands with airborne hyperspectrometer over a desert site and validation over a vegetation area. A comprehensive field campaign was carried out at the Baotou site in Inner Mongolia, China in September 2021. During the field campaign, the solar reflective images observed by Copernicus Sentinel-2/MSI on September 20th and 23th 2021, Chinese Gaofen-7/DLC on September 20th, 21th, Gaofen-6/WFV on September 23th 2021 were collected. At the time of space-borne sensors overpassing the Baotou site, airborne hyperspectral datasets were acquired by an airborne hyperspectrometer mounted on a high-altitude aircraft (~8000 m) in approximately the same viewing geometry as the space-borne sensors. Additionally, the surface reflectance and atmospheric parameters including aerosol optical thickness and water vapor content were also measured synchronously through SI-traceable ground instruments that operate at the site. Firstly, the Sentinel-2/MSI, Gaofen-6/WFV and Gaofen-7/DLC were transfer calibrated with airborne hyperspectral datasets over the desert site. Then, the radiometric benchmark transfer calibration results were validated with the at-sensor radiances of Sentinel-2/MSI, Gaofen-6/WFV and Gaofen-7/DLC over the vegetation area, which were modeled using MODTRAN-5 radiative transfer code based on in-situ measurements. The validation results show that the relative errors between modeled and transfer calibrated at-sensor radiances are 4.54%, -4.57% and 2.20% for Sentinel-2/MSI, Gaofen-6/WFV and Gaofen-7/DLC, respectively. Preliminary uncertainty analysis was also discussed and the results indicate that the overall uncertainty of the radiometric benchmark transfer calibration is less than 4.0%. Compared with the reflectance-based radiometric calibration approach, the transfer calibration method can better monitor the radiometric performance of the space-borne solar reflective bands with lower uncertainty. Future studies will focus on how to determine comprehensive radiometric calibration results and uncertainties when using various radiometric calibration methods, which will be carried out in collaboration with the National Institute of Metrology.
This submission has been accepted for a presentation and a poster, but some material not been published yet by the authors.
Topic : Theme 1: Biosphere Monitoring.
Reference : T1-D10
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