Lunar exploration phase III: Launch window and trajectory design for a lunar lander

The lunar exploration phase III mission is a part of the China Aerospace Science and Technology Corporation’s lunar exploration program that will perform a soft-landing and sample return from the Moon to test the key technologies that are required for human lunar missions. This paper focuses primarily on the trajectory design and orbital launch window generation for a lunar probe that are consistent with the constraints imposed by third phase of lunar exploration. Two categories of trajectories are explored: Earth-to-Moon and Moon-to-Earth. With the patched conic technique, the analytical and modified analytical models of the transfer trajectories are developed. The requirement of high-latitude landing for the return phase trajectory is considered in the modified model. By varying the initial input conditions and with a fast convergence iteration scheme, different characteristics of the transfer trajectory are generated. The orbital launch windows are established to study the mission sensitivities to time and fuel consumption and to provide a launch timetable that is compatible with this mission’s requirements. The lunar surface stay time is analyzed for different conditions. The high-fidelity gravitational model is introduced to demonstrate the accuracy and convergence behavior of the analytical solution. The design method can also be used as a basis for the future human lunar missions.