An increasing demand for investigating the solar system has envisioned many asteroid exploration missions. Optical navigation is the principal technology to determine the explorer’s orbit relative to an asteroid when approaching it in an exploration mission. The approaching orbit determines the observing conditions and consequently affects the optical navigation accuracy. Aiming at improving the optical navigation performance, this article proposes the approach orbit optimization method considering optical navigation observability. The defect of the optical navigation along the line-of-sight (LOS) direction when the explorer moves along the conventional approaching orbit is revealed. The quantitative index of the navigation performance is designed by deriving the Fisher information matrix (FIM). The orbit optimization problem is constructed by involving the elements of FIM and fuel consumption together into the optimization index, and setting up the necessary engineering constraints. Numerical simulations show that compared with the conventional fuel-optimal cases, the navigation along the LOS direction is greatly improved. The navigation accuracy is improved from 86 to 99% and an additional 1.62 kg of fuel is consumed. The proposed method can effectively improve the navigation performance and has promising applications in asteroid approach trajectory design in the future asteroid exploration missions.

中文翻译：

---

考虑光学导航可观测性的小行星临近轨道优化

对调查太阳系的需求不断增加，已经设想了许多小行星探索任务。光学导航是在探索任务中接近小行星时确定探索者相对于小行星的轨道的主要技术。接近轨道决定观测条件，进而影响光学导航精度。以提高光学导航性能为目标，提出了考虑光学导航可观测性的进近轨道优化方法。揭示了探测器沿常规接近轨道移动时沿视线（LOS）方向的光学导航缺陷。通过推导Fisher信息矩阵（FIM）设计导航性能的量化指标。轨道优化问题是通过将FIM和燃料消耗的要素一起纳入优化指标，并设置必要的工程约束来构造的。数值模拟表明，与传统的燃料最优情况相比，沿LOS方向的导航得到了极大的改善。导航精度从 86% 提高到 99%，额外消耗 1.62 千克燃油。所提方法可有效提高导航性能，在未来小行星探测任务中的小行星进近轨迹设计中具有广阔的应用前景。沿 LOS 方向的导航得到很大改善。导航精度从 86% 提高到 99%，额外消耗 1.62 千克燃油。所提方法可有效提高导航性能，在未来小行星探测任务中的小行星进近轨迹设计中具有广阔的应用前景。沿 LOS 方向的导航得到很大改善。导航精度从 86% 提高到 99%，额外消耗 1.62 千克燃油。所提方法可有效提高导航性能，在未来小行星探测任务中的小行星进近轨迹设计中具有广阔的应用前景。