While “BepiColombo” may be an unfamiliar word to most people, it is in fact the name of a survey mission to Mercury by the ESA. The planet closest to the sun, Mercury has several peculiar characteristics, one of which is its 2:3 relation between the periods of rotation and revolution. This fact was discovered by the Italian applied mathematician Giuseppe (Bepi) Colombo (1920-1984). Named after him, the BepiColombo is one of ESA’s cornerstone missions, and its three satellites/landers are expected to illuminate the mysteries of Mercury’s interior as well as those of the surface and magnetosphere. The three satellites/landers are as follows.

   MPO: Mercury Planetary Orbiter
   MMO: Mercury Magnetospheric Orbiter
   MSE: Mercury Surface Element.

Regarding the launch method, at present the basic plan is to launch the mission using two Russian Soyuz-Fregat rockets in 2009. One will include an MPO while the other will have an MMO+MSE. Both are expected to be injected into the Mercury orbit by two-types of liquid chemical propulsion using electrical propulsion and Venus swing-by.

While BepiColombo was planned by ESA, ISAS and ESA have been discussing ways to make it a joint mission. As a result, ISAS will take charge of the system design, manufacture and operation, while forging ahead with a plan to entrust the scientific aspect (including MPO and MSE) to international cooperation centering on Japan and Europe. While ISAS satellites have carried observation systems from NASA or Europe in the past, If this project is realized, ISAS will play a part of this important ESA mission and usher in a new style of international cooperation. Based on conclusions drawn by the ESA’s SSAC (Space Science Advisory Committee) held in the mid-September, the BepiColombo plan was formally acknowledged as the fifth cornerstone (CS-5) by SPC (Science Program Committee) held on October 11 and 12. This adds impetus to further discussion of the possibility of a joint-mission project.