首页 > , Vol. , Issue () : -
基于伪不变定标场（PICS）的大气层顶反射率（TOA）模型直接计算卫星过境入瞳辐亮度而无需地面测量，为高频次在轨辐射定标及长期性能监测提供了有效技术手段。然而由于严格的空间均匀性、时间稳定性和大气条件要求，现有的PICS定标场均分布在境外而难以满足多在境内成像的国产陆地卫星等定标需求。借鉴PICS的定标思路，本文开展了放宽场地、大气稳定性约束条件的我国陆表稳定目标TOA反射率模型构建方法研究。以我国西北区域的格尔木沙地稳定目标为例，将约束条件放宽至场地面积>3km×3km、云覆盖率<60%、空间均匀性<3%、时间稳定性<10%（11年），利用11年的Aqua/MODIS与ECMWF再分析资料分析观测几何及大气参数对TOA反射率的规律性影响，引入地表/大气辐射传输模型中定义的散射角，进一步表征TOA反射率模型中地表-大气间多次散射贡献，构建了一种适用于我国陆表稳定目标的TOA反射率模型。该模型系统偏差小于-0.10%，均方根误差小于0.0084；将Sentinel-2A/B MSI和Landsat-8/OLI的TOA反射率与本文模型计算TOA反射率进行比较，模型计算TOA反射率与Sentinel2A/B MSI观测TOA反射率的平均相对误差小于1.44%，标准差小于1.59%；与Landsat-8/OLI观测TOA反射率的平均相对误差小于1.77%，标准差小于2.11%。验证结果表明本文提出模型的计算值与卫星观测值具有较高的一致性和稳定性，能够应用于其他太阳反射谱段卫星载荷的在轨辐射定标和长期辐射特性监测。
The TOA reflectance model based on pseudo-invariant calibration sites (PICS) can directly calculate the apparent radiance of a satellite sensor without ground measurement, which provides an effective technical approach for high frequency in-orbit radiometric calibration and long-term satellite performance monitoring. However, due to the strict requirements of spatial uniformity, time stability and atmospheric conditions, the existing PICS calibration sites are all distributed abroad and it is difficult to meet the calibration requirements of China land satellites, which are mostly imaging in China. Using the experience of the radiometric calibration idea of PICS, this paper studied the construction model of TOA reflectance for inland surface stable target with relaxed sites and atmospheric stability constraints. Taking the stable target of Golmud destet in the northwest region as an example, the constraints were relaxed to site area greater than 3km×3km, cloud coverage less than 60%, spatial uniformity less than 3%, and temporal stability less than 10% (11 years). Then, Aqua/MODIS and ECMWF reanalysis data of 11 years were used to analyze the regularity of the observation geometry and atmospheric parameters on the TOA reflectance, and the scattering angle defined in the surface/atmospheric radiation transmission model was introduced to further characterize the multiple scattering contribution between the surface and atmosphere in the TOA reflectance model. Finally, a TOA reflectance model suitable for inland stable targets was proposed. The averaged bias and RMSE of the model is less than 0.10% and 0.0084, respectively. In addition, the TOA reflectance directly observed by Sentinel-2A/B MSI and Landsat-8/OLI were compared with the TOA reflectance calculated by the proposed model. The average relative error between the TOA reflectance calculated by the model and the observations of Sentinel2A/B MSI is less than 1.44%, and standard deviation of the relative error does not exceed 1.59%. The average relative error with Landsat-8/OLI observations is less than 1.77%, and the standard deviation of the relative error does not exceed 2.11%. The validation results show that the calculated TOA reluctances of the proposed model have high consistency and stability with satellite observations, and the model can be applied to the on-orbit radiometric calibration and long-term radiation characteristics monitoring of other satellite payloads in solar reflection spectrum.