Abstract
In order to complete the high-precision calibration of the planetary rover navigation camera using limited initial data in-orbit, we proposed a joint adjustment model with additional multiple constraints. Specifically, a base model was first established based on the bundle adjustment model, second-order radial and tangential distortion parameters. Then, combining the constraints of collinearity, coplanarity, known distance and relative pose invariance, a joint adjustment model was constructed to realize the in orbit self-calibration of the navigation camera. Given the problem of directionality in line extraction of the solar panel due to large differences in the gradient amplitude, an adaptive brightness-weighted line extraction method was proposed. Lastly, the Levenberg-Marquardt algorithm for nonlinear least squares was used to obtain the optimal results. To verify the proposed method, field experiments and in-orbit experiments were carried out. The results suggested that the proposed method was more accurate than the self-calibration bundle adjustment method, CAHVOR method (a camera model used in machine vision for three-dimensional measurements), and vanishing points method. The average error for the flag of China and the optical solar reflector was only 1 mm and 0.7 mm, respectively. In addition, the proposed method has been implemented in China’s deep space exploration missions.
Highlights
With the continuous development of aerospace technologies, many countries have carried out extensive exploration of extraterrestrial bodies, such as to the moon and Mars [1,2,3].To successfully conduct these tasks, such as planetary rover navigation, high-precision mapping of the detection area, the determination of interior orientation (IO) elements, exterior orientation (EO) elements, and distortion parameters of the cameras are of great significance [4,5]
To test thehigh-precision accuracy of the proposed feature-based self-calibration model,the various types of experiments were carried out in a general laboratory, the simulated experimental field in-orbit test, the dimensions of the national flag, solar panels, and other com built by the China Academy of Space Technology (CAST), and under in-orbit conditions used
Accurate IO elements of the stereo camera are crucial for the in-orbit navigation and positioning of planetary rovers
Summary
With the continuous development of aerospace technologies, many countries have carried out extensive exploration of extraterrestrial bodies, such as to the moon and Mars [1,2,3]. Self-calibration is achieved by taking at least two images with a certain degree of overlap and establishing the epipolar transformation relationship to solve the Kruppa equation This method has low accuracy and poor stability, and the Kruppa equation has the singular value problem [9,10]. The above methods have achieved promising results, the in-orbit stereo camera calibration in the deep space exploration missions needs to be implemented in accordance with the actual conditions of each country. (4) The proposed method can provide a reference for in-orbit camera calibration of planetary rovers in the deep space exploration missions of all countries.
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