准确地获取地表双向反射特性是遥感辐射定标和卫星全链路成像仿真的重要基础。在野外条件下通常使用实测的双向反射因子(BRF)反演得到双向反射分布函数(BRDF)。仿真分析显示,大气能见度分别为23 km和15 km时,同一地表的BRF方向性系数相差19%。野外条件下实测的BRF因受大气散射的影响而不能准确表征地表方向反射特性。通过同步测量2π空间内的大气散射,提出一种BRDF反演方法。该方法将BRF实测值与测量模型计算值之间的残差作为反演的代价函数,以消除大气散射的影响,可反演地表真实的BRDF模型特征参数。结果证明方向反射特性是地物的固有属性,不随测量环境辐射的变化而变化。

Accurate acquisition of the bidirectional reflectance characteristic of surface is essential foundation of radiometric calibration and satellite full-chains imaging simulation. Bidirectional reflectance distribution function (BRDF) is retrieved by measured BRF in field environment. The simulation result shows that the relative difference between the BRF directional coefficients of the same surface is 19% when atmospheric visibility is 15 km and 23 km, respectively. Therefore the true directional reflectance feature can’t be characterized by measured BRF in field environment due to the effect of atmospheric scattering. We propose a BRDF retrieval method, by the synchronous measurement of atmospheric scattering radiation in 2π solid angle. In this method, the residual between measured BRF and value calculated by measurement model is used as the cost function in inversion process, the effect of atmospheric scattering is deducted and the true BRDF parameters of surface are retrieved. The bidirectional reflectance characteristic is inherent attribute of surface and does not change with environment radiation.