Investigation on the development of deep space exploration

Deep space exploration is the term used for the exploration of the Moon and the celestial bodies or space beyond the Moon, which is an important part of human space activities. Firstly, the development of deep space exploration (not including the Moon) during the last few decades is summarized. Secondly, the development trend of different space countries and regions is analyzed. Then the experience and enlightenment of deep space exploration are briefly discussed. Some suggestions for China's future deep space exploration are given in the end.