Research On 3D Reconstruction Of Small Body Based On Stereophotoclinometry

Carrying out exploration activities for small bodies in the solar system can help human beings understand the mysteries of the universe in depth,and which advances the development of aerospace technology to a deeper level.Due to the small size of the small bodies,the weak gravitational environment,and the lack of sufficient a priori knowledge,the descent of the detectors is the process of space rendezvous of non-cooperative objects.Compared with celestial bodies such as the Moon and Mars,the exploration of small bodies requires higher navigation accuracy and more accurate measurement and control technology,which is the only way for China to move from a large space nation to a powerful space nation.China started late in the exploration of small bodies,but the planned quasi-satellite 2016HO3 asteroid attachment sampling and the multi-mission exploration of the main belt comet 133 P orbiting,which have far-reaching significance for solving scientific and engineering problems.During the sampling process of small bodies attachment,relative terrain navigation on the orbit autonomous terrain requires accurate 3D model support,so it is very important to study a high-resolution and high-precision 3D modeling method.Based on the existing small bodies exploration tasks,this paper studies the 3D modeling methods and scientific loads used in each stage of the small body exploration vision task,and proposes a phased modeling method for small body 3D modeling.The main research contents of this paper are follows.First,based on the built simulation environment,this paper generated observation data for small body modeling and dynamic parameters estimation.In the small bodies exploration missions,due to the limited communication delay and the storage space of the loading equipment,it is necessary to return the most effective data.Moreover,the accuracy of optical 3D modeling depends on the quality of the image data.Therefore,this paper proposes an observation trajectory constraint method based on observation and illumination conditions.Second,the 3D modeling method based on stereo geometry in this paper realizes the initial model of stereophotoclinometry 3D modeling.The stereophotoclinometry modeling method is essentially an iteratively optimized stereo modeling method,so this paper implements a 3D modeling method based on stereophotogrammetry.The results show that the sparse reconstruction result based on structure from motion can be used as the initial model for stereophotoclinometry modeling;the dense model based on multi-view stereo has rich surface texture features.In order to compare the stereophotogrammetry and stereophotoclinometry 3D models in the same world coordinate system,this paper implements the method of alignment of the 3D model based on the pose of the cameras,and preliminary analysis of the orbit error of the 3D modeling.Third,this paper studies the overall process of the 3D modeling method of small bodies based on stereophotoclinometry,and realizes the 3D reconstruction of local terrain.Aiming at the problem of insufficient use of images information in stereophotogrammetry,3D modeling method based on stereophotoclinometry is studied,including Landmark selection,Landmark matching and tracking method based on Harris-SIFT in proximity range,and photometric-based terrain optimization,camera extrinsics estimation based on stereo geometry,conversion of digital elevation map to triangular facet model and last but not unimport global model fusion method.