Abstract: The flight trajectories from low earth parking orbit (LEO) to low lunar parking orbit (LLO) based on a planar three-body model are studied. Trajectories and some key parameters of the three stages, the earth escape stage, coast arc stage, and lunar capture stage, are presented as well. The concept of “coverage apogee” and the selenocentric energy are first, respectively, introduced to accomplish the terminal point determination of the earth escape stage and the initial point determination of the lunar capture stage.

Key words: lunar p robe, lunar t rajecto ries, low th rust, p roblem ofN bodies, op t imal cont ro l