Japanese first interplanetary mission PLANET-A for Halley’s comet exploration was successfully completed when the two spacecraft launched by M-3SII rockets, passed by the comet on March 8 and 11, 1986, and made scientific measurement. This paper gives a description of the M-3SII rocket, the latest version of the Mu launch vehicle. History of development, vehicle composition and a typical flight profile are presented with a review of the two successful flights.
