Autonomous navigation technology has played an increasingly important role during modern planetary exploration missions. The image-based optical navigation method is one of the most promising solutions for autonomous navigation. Previous studies have mainly focused on image processing and navigation filtering algorithms. Classic ellipse fitting approaches rely on the least square method, which may fail in the case of short-arc ellipse fitting. This paper proposes an optimization method with a priori shape information to achieve a high-precision short-arc ellipse fitting. First, by querying the ephemeris and using the projection principle, the projected ellipse of the entire planet can be obtained. Second, the shape information of the ellipse that represents the useful priori information can be extracted using the least squares ellipse fitting algorithm. Third, the shape information is introduced into the standard elliptic equation, whose parameters are optimized to fit the planetary edge arc obtained by the navigation camera. Finally, simulations are conducted and the results show that the proposed method performs better in the accuracy of short-arc ellipse fitting compared to the traditional least squares method.

自主导航技术在现代行星探索任务中起着越来越重要的作用。基于图像的光学导航方法是自主导航最有希望的解决方案之一。先前的研究主要集中在图像处理和导航过滤算法上。经典的椭圆拟合方法依赖于最小二乘法，这在短弧椭圆拟合的情况下可能会失败。提出了一种具有先验形状信息的优化方法，以实现高精度的短弧椭圆拟合。首先，通过查询星历表并使用投影原理，可以获得整个行星的投影椭圆。第二，可以使用最小二乘椭圆拟合算法提取表示有用先验信息的椭圆的形状信息。第三，将形状信息引入标准椭圆方程，优化其参数以适合导航摄像机获得的行星边缘弧。最后进行了仿真，结果表明，与传统的最小二乘方法相比，该方法在短弧椭圆拟合中的精度更高。