Navigation Feature Extraction And Pose Estimation Algorithm Of Small Celestial Spacecraft’s Landing Segment

Visual navigation using high-resolution navigation cameras is one of the effective landing navigation methods for small object spacecraft.However,in the landing segment of small object spacecraft,the visual navigation algorithm of spacecraft based on traditional navigation land markers such as feature points and craters may suffer from insufficient feature extraction and mis-matching,which affect the navigation process.It is important to make full use of the existing observation information as new navigation land markers.The projection of the solar sail of the small object probe as a self-contained feature is directly related to the probe attitude and can be used as a landing segment navigation land marker.At the same time,when the projection cannot be extracted,irregular curved edge features such as rocks and pits,which do not have fixed geometry,can be used as navigation land markers for probe attitude estimation.Therefore,this paper investigates the algorithm of small object probe landing segment navigation feature extraction and attitude estimation.The main research contents of the paper include.Firstly,the solar sail projection and the irregular curve feature on the surface of the small object are selected as the navigation land markers for the characteristics of the landing section of the small object spacecraft.If the solar sail projection is detected in the navigation image,the solar sail projection is extracted and fitted by the threshold segmentation,edge extraction and convex edge extraction algorithms,and the projection length and angle are detected.If the solar sail projection is not obvious in the navigation image,the image pyramid is constructed to extract irregular curves in the scale space,construct irregular curve descriptors,and match them in the sequence image using the Euclidean distance constraint and the nearest neighbor distance ratio principle.Finally,the detection and matching effects of the two navigation features are verified in real images,respectively.Secondly,the estimation method of the position attitude based on the projection of the spacecraft solar sail is investigated.Based on the projection extraction results,the angular changes of the spacecraft pitch and roll angles are solved by using the projection transformation relations,the rotation correction is applied to the image to be matched,and then the changes of yaw angle and spacecraft position are solved by template matching,and finally the algorithm is verified by simulation experiments under the possible noise intensity Finally,the reliability and navigation accuracy of the algorithm are verified by simulation experiments under the possible noise intensity.Finally,the spacecraft positional estimation method based on the matching of irregular edge curves on the surface of small objects is investigated.The irregular curve obtained by matching in the sequence image consists of discrete points,and the polynomial curve analytic formula is constructed using three adjacent points,and the feature points extracted by the feature point detection algorithm are selected instead of the curvature maximum points,and the changes of the probe position and attitude in three consecutive navigation images are solved by three-view geometric constraints.The simulation results show that the spacecraft attitude estimation algorithm using irregular curves combined with feature points can effectively estimate the spacecraft attitude in the landing section of the small object spacecraft,and can provide a theoretical basis for the design of autonomous navigation systems.