Suisei

Planet-A

Mission Profile

Suisei (Planet-A) was JAXA's first interplanetary spacecraft, launched on 18 August 1985 aboard a Mu-3S2 rocket to conduct a flyby of Halley's Comet during its 1986 apparition as part of the international Halley Armada. The spacecraft carried an ultraviolet imager to photograph the hydrogen corona surrounding the comet's nucleus, making the first UV images of a cometary hydrogen coma from space and contributing to understanding of cometary water production rates. Suisei passed within 151,000 km of the comet's nucleus on 8 March 1986, complementing the closer flyby of its sister spacecraft Sakigake and ESA's Giotto. The mission established JAXA's deep space exploration capability and provided Japan's first direct measurements of a cometary environment.