3D Modeling And Rotation Axis Direction Estimation For The Approach Phase Of Small Celestial Body

Digging up effective information of small objects in the universe is an important way to understand the origin and evolution of the solar system,and it has great scientific value.In recent years,our country is tackling key problems in the detection of small celestial bodies.The space environment of the universe is complicated,the shape and motion state of small celestial bodies have a certain degree of uncertainty,which puts forward higher requirements for the technology of long-distance flight navigation and obtaining effective information of celestial bodies.Therefore,when the observation conditions of the proximity segment detection are limited,accurate flight navigation and efficient acquisition of the depth information of small celestial bodies are conducive to the smooth progress of the mission research in the subsequent stage of the detector and have important research significance.In the approaching section of deep space exploration,the spacecraft uses the target celestial body as a guide for navigation work,so the result of the centroid extraction of the small celestial body directly affects the accuracy of the navigation work.At the same time,the direction of the rotation axis and the model parameters are calculated based on the inversion of the brightness of the small celestial body at this stage,which can not only provide good reference information for the subsequent algorithm to accurately solve the direction of the rotation axis,but also estimate the initial three-dimensional size of the small celestial body.Aiming at the above tasks,this paper uses the small celestial body image sequence taken by the detector's narrow field of view camera in the close section to elaborate and implement the three-dimensional modeling of the small celestial body based on the light curve and the estimation method of the rotation axis direction.The main research contents are:1.In the long-distance detection stage,the star table is parsed according to the conversion relationship between the celestial coordinate system,the space coordinate system and the camera imaging coordinate system,and a reasonable stellar imaging model is established to simulate the qualified starry sky background during observation,combined with the simulation image as the experimental data set of this article.2.When the small celestial body appears as a point target state in the observation field of view,the cross-correlation algorithm based on the point spread function is used to detect the small celestial body.In view of the large error of the calculated centroid position,a centroid extraction method based on correlation filtering is proposed.Experimental results show that this method effectively solves the limitation of using a single point spread function as a template in the algorithm,and makes the result of solving centroids have higher accuracy.At the same time,in the short-distance detection stage,SIFT feature extraction and matching are performed on the image sequence of small celestial bodies captured by flight,which is used to solve the relative distance between the detector and the target celestial body at the current moment.3.Aiming at the change of illumination angle,the target celestial body can only be partially imaged in the field of view,a three-axis ellipsoid model is used to model the target in three dimensions.Observe it under different flight conditions,draw and fit its brightness change curve,and use the information of the light curve to estimate the rotational angular velocity of the target celestial body,and finally calculate the rotation of the target celestial body's axis orientation and 3D model parameters by solving the nonlinear equations,and verify the accuracy of the method.