Imaging Simulation Method for Studying the Fold Surface of Space Targets

To obtain high quality simulation images of a space target, simulating the folded surface of the target covered temperature-controlled material is important. This study employed the inverse ray tracing method to establish a radiation transfer model. The aim of this study is to calculate the secondary reflection that occurs on the folded surface of a polyimide material and the Fresnel reflection of the material. The cosine weight importance sampling method was used to optimize the ray interval during the calculation of the secondary reflection. Consequently, the bidirectional reflection distribution function (BRDF) model, which can describe the Fresnel reflection, was improved. Using a three-dimensional software program for generating and quantifying the fold plane, the root mean square error of importance sampling on severe folds was reduced by 63.42% compared with uniform sampling. Moreover, compared with the measured BRDF model, the improved BRDF model can better describe the Fresnel reflection and discrete strong mirror reflection spots were observed in the simulation image of the fold plane. Furthermore, the simulated satellite image shows the detailed texture of the folded surface effectively, and the shadow effect is realistic, which can provide image for the research of space target visual navigation algorithm.