关键词: 地月往返轨道, 嫦娥五号, 嫦娥六号, 月球背面采样返回, 轨道动力学, 任务规划

Abstract: China has successfully completed three consecutive Earth–Moon round-trip exploration missions, encompassing a circumlunar free-return flight, a lunar nearside sample-return mission, and the first-ever lunar far-side sample return mission. Leveraging fundamental classical celestial mechanics theory and flight-proven engineering experience accumulated from prior lunar exploration programs, the trajectory design team has developed a systematic theoretical and methodological framework dedicated to Earth–Moon round-trip trajectory design. This framework unifies three core theoretical pillars: the three-body dynamic modeling theory for the Earth–Moon system, the analytical perturbation theory for lunar orbits, and the geometric invariance theory for Earth–Moon transfer trajectories. Building on this framework, the team has achieved systematic breakthroughs in a suite of critical enabling technologies, including circumlunar free-return trajectory optimization, trans-Earth injection (TEI) strategy design, lunar orbit rendezvous (LOR) trajectory planning, highly elliptical frozen orbit design, and end-to-end integrated mission planning. These technical advances have enabled the robust implementation of a diverse set of lunar mission scenarios, including circumlunar return, prograde and retrograde lunar orbit insertion, high-latitude landing in both lunar hemispheres, and nearside and far-side sampling return. This paper provides a systematic review of the evolutionary development of these theories and methodologies, alongside a comprehensive summary of flight-validated engineering experience accumulated via their on-orbit deployment. The objective of this work is to provide a foundational technical reference for the trajectory design in future lunar and deep space exploration missions.

Key words: Earth–Moon round-trip trajectory, Chang’E-5, Chang’E-6, lunar far-side sample return, orbital mechanics, mission planning