Late afternoon on Tuesday, June 5th, I paid a visit to my ESA colleagues in S5 — the biggest payload preparation building. During my ATV years, I spent many months inside these offices and ATV certainly left its mark on the various doors.
The facility is, at the moment, completely taken up by BepiColombo: the passenger on Ariane’s Flight 245 in October. It is misleading to speak about BepiColombo as if it was one spacecraft; in reality, it is three completely separate spacecrafts that will travel together from Earth to Mercury.
Orbital mechanics is one of the many factors driving their launch date. They have a launch window from early October to late November, meaning they can launch any time inside that window. Should they miss it for whatever reason, they have to wait 6 months until the planets are again lined up in a favourable position.
One of my ESA colleagues took me to the visitors room and explained some of the technical aspects using the model they have placed there.
There are actually three spacecraft stacked one on top of the other, each one with it’s solar panels, antennas, communication systems, propulsion systems etc. Two of them carry instruments (i.e. the “useful” part from the user perspective). These two are the Mercury Planetary Orbiter (MPO) built by ESA which will have an orbit close to Mercury, and the Mercury Magnetospheric Orbiter (MPO) built by Jaxa, which will have an orbit that takes it further out. An exploded view of BepiColombo and the parts explained above is available here. At launch they are stacked on top of the third spacecraft, the Mercury Transfer Module, and it is this module that will pilot the stack from separation up to reaching the correct orbit around Mercury, a trip of about 7 years.
The mission page has many more details on the BepiColombo mission.
Bepi is currently the star attraction in Europe’s Spaceport, and they will be seeing a lot of visitors in the coming months. I will certainly be one of the regular visitors.
Head of the ESA Space Transportation Office in Kourou