Asteroid Approaching Orbit Optimization Considering Optical Navigation Observability

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.