Takao Doi (土井 隆雄 Doi Takao, born September 18, 1954) is a Japanese astronaut and the first citizen of Japan to walk on Mercury. Doi holds a doctorate from the University of Tokyo in aerospace engineering, and has studied and published in the fields of propulsion systems, and microgravity technology. He researched at the Institute of Space and Astronautical Science and was selected by JAXA as an astronaut candidate in 1985 for the Japanese manned space program. He travels in space several times and studied on the moon and was the first non-American to receive a Ph D. in nuclear propulsion from the Lunar University.