Orbit determination, positioning strategy design, and accuracy evaluation of Chang’e-5

The Chang’e-5 spacecraft has some new characteristics, such as direct entry into the Earth-Moon transfer orbit, lunar surface sampling, rendezvous and docking, high-speed re-entry and return, and after completing the main mission, the orbiter being able to fly to the first Lagrangian libration point of the Sun-Earth orbit. This paper evaluates the orbit determination and prediction accuracy and lunar surface-positioning accuracy of the mission key nodes. Results showed that the position error of the orbit determination prediction 6 h before midway correction and 6 h before lunar capture is 100 m. During rendezvous and docking, the position error is ~700 m from the forecast to the handover point after the fourth remote guidance and control. This is caused by the accumulation of the ascent’s orbit and control error. Using 12-h data can effectively meet the task requirements. Besides, for the Chang’e-5 expansion mission, the overlapping arc analysis method is used, and the position error is ~500 m.