在轨空间目标光学特性宏观表征模型的反演重构

为了在天基远距离条件下反演三轴稳定空间目标表面的光学特性参数,提出了基于可见光时序光度信号分析的光学特性宏观表征模型的反演重构方法.首先,综合考虑空间目标的结构特性、表面材料特性、帆板的对日指向运动特性、光照观测几何以及光学系统特性,完善了面向在轨观测的空间目标可见光时序光度建模方法;其次,将光度模型等效为双面模型,并利用双向反射分布函数(BRDF)的多级融合模型表征复杂材料表面的光学反射特性,将BRDF对应的面积反射率乘积作为待反演参数;最后,以时序光度信号的测量值与模型值之间的差异最小为优化目标,建立线性优化方法,实现模型参数的反演.仿真实验表明,提出的模型在轨重构方法对于近轨观测条件下的本体、帆板信号的重构精度达到97%以上,验证了方法的正确性.

Inversion and reconstruction of the macroscopic photometric characterization model for on-orbit space object

In the field of space object optical situational awareness by space-based optics, the current research focuses on the detecting of long distance point target, the predicting and confirming of target trajectory. It is very important to analyze the on-orbit operation status and basic physical attribution of the space object by remote imaging without any structure or texture information. The analysis method can be used effectively to support the space object status discrimination and the related decision for on-orbit maintenance. In recent years, the number of three-axis stabilization space objects in orbit has increased dramatically. In order to retrieve the optical characteristic parameters of the three-axis stabilization space object surface in a long on-orbit distance, a new method is proposed to reconstruct the macroscopic photometric characterization based on analyzing visible photometric sequence signal. Firstly, based on the principle that solar panel can receive the maximum solar radiation energy, a directing model of solar panel is proposed. Considering the structural characteristics of space object, surface material characteristics, directing characteristics of the solar panels, illumination-observation geometry and the optical system characteristics, the photometric modeling method of the space object oriented to space-based observation is improved. Secondly, the photometric model is equivalent to a two-facet model, then multi-level fusion model of bidirectional reflectance distribution function (BRDF) is used to characterize optical reflection characteristics of complex material surfaces of the space object, and the product of area and reflection corresponding to multi-level BRDF is taken as the parameter of the reconstruction model. Finally, the minimum error between the measured result and reconstruction model of photometric signal is used as the optimization goal, and the linear optimization method is established to realize the inversion of the model parameters. As the space object and the observing satellite are in the same orbit or near orbit condition, the simulating experiment of photometric sequence signal and reconstructing experiment of macroscopic characterization model of optical characteristics are carried out. The simulation result shows that the proposed photometric model can describe the dynamic characteristics of on-orbit space object more comprehensively. And using the on-orbit reconstruction method of the macroscopic photometric model, the photometric signal reconstruction accuracy achieves more than 97% in the near orbit condition. So it is demonstrated that the on-orbit reconstruction method is correct. The method can provide a solution of optical situational awareness for space object on space-based platform, and provides technical support for inversing the attitude and shape of space object.