Follow-on missions of Sakigake and Suisei

The paper discusses follow-on missions of two Japanese Halley's comet explorer Sakigake (a forerunner) and Suisei (a comet). Several options including Venus, Mars and comet(s) fly-by missions are studied, and the selected plan for each spacecraft is shown as follows: Utilizing the earth gravity assist maneuvers started in 1992, the spacecraft Sakigake will remain in the vicinity of the earth for several years and will offer invaluable complemental data to the ISTP (International Solar Terrestrial Physics) program. The spacecraft Suisei will also swing-by the earth in 1992 and will encounter with the comet Giacobini-Zinner in 1998. It is shown that, on the way to Giacobini-Zinner, the Suisei may also approach to another comet Tempel-Tuttle if this comet will appear again in 1998. It is anticipated that Sakigake will also explore two comets, Honda-Mrkos-Pajdusakova in 1996, and Giacobini-Zinner in 1998. The outline of selected mission for each spacecraft is described. Also the procedure of velocity correction maneuvers, which were carried out in January, 1987 for Sakigake and in April, 1987 for Suisei to make the spacecraft swing-by the earth in 1992, is expressed. The results of orbit determination after these maneuvers show that they were successful.