SfS-Based 3D Modeling And Rotation Parameter Estimation Of Small Body

Small body exploration has been the research hotspot and main direction of deep space exploration in recent years.Many countries and organizations such as the United States,Europe and Japan have successively carried out exploration tasks for small bodies.The exploration of small bodies can not only help scientists explore the origin and evolution of the solar system,but also has great significance for enhancing the national independent innovation capability and promoting the development of science and technology.Due to the characteristics of small size,small gravity,and difficult observation,compared with the detection tasks of large bodies such as the moon and Mars,there are still some urgent needs to be solved in the missions of modeling,navigation,landing sampling,etc.The scientific and technological problems pose greater challenges to scientists.The 3D model is the basic data of small bodies,and has important reference value for relative navigation of terrain and selection of landing points.How to model small bodies in 3D has always been a difficult task in the detection mission.This paper proposes a 3D modeling method for small objects based on SfS(Shape from Silhouette).We can still get a more refined three-dimensional model using the outline information of the small body in the pictures when the specific terrain features cannot be observed,and the simulation experiment of Bennu asteroid is verified on the simulation platform based on CINEMA-4D.The motion parameters of the small objects are the scientific data of the small objects,and are also an important basis for the detector's descent and landing process.The difficulty of motion parameter estimation is the estimation of rotation direction and rotation angular velocity.This paper proposes a small body motion parameter estimation method based on the Extended Kalman Filter.Simulation experiments are carried out on the regular cube and 67p/Churyumov-Gerasimenko comet model,and the influence of various factors on the accuracy of the method is analyzed in detail,which provides a certain reference value for scientific research.The main research contents of this article are as follows:1.Introduced the development status of 3D modeling and motion parameter estimation at home and abroad and its application in the task of small body exploration and analyzed the advantages and disadvantages of various methods;2.The 3D modeling method of small bodies based on SfS is studied.First,the maximum variance method is used to extract the contour information of small bodies in the simulated image,and then the voxel modeling is converted into a pseudo-Boolean function minimization problem.A local minimization search algorithm is proposed.Aiming at the problems of excessive use of computing resources and low execution efficiency of the local search algorithm in practical applications,a hierarchical search algorithm based on octree is proposed on the original basis,which significantly improves the performance of the algorithm.The corresponding simulation experiment and the comparision experiment of the two algorithms are carried out on the Bennu asteroid model;3.The small body motion parameter estimation method based on the Extended Kalman Filter is studied.First,the corresponding system model is established for the asteroid observation scene,and the camera coordinate system,the small body coordinate system and the conversion relationship between them are defined,and then the state variables and state equations are defined.The overall solution process is designed,the correctness of the method is verified on the regular cube model,and the influence of various factors on the accuracy of the method is analyzed in detail on the 67p comet model.