BepiColombo will consist of three modules: a European orbiter, a Japanese orbiter and a transfer module carrying the two spacecraft to Mercury. The complete unit will have a height of approximately five metres and a mass of about three tonnes, of which about 50 per cent is propellant.
The European Mercury Planetary Orbiter (MPO) will be equipped with eleven sophisticated scientific instruments. Flying in a polar orbit, it will study Mercury for at least a year, imaging the planet’s surface, generating height profiles, and collecting data on Mercury’s composition and atmosphere.
The Japanese Mercury Magnetospheric Orbiter (MMO) will investigate the planet’s magnetic field with its five on-board instruments.
One of the greatest challenges facing Astrium engineers is preparing BepiColombo for the extreme temperatures it will encounter. Close to Mercury, solar radiation is up to ten times stronger than on Earth, with temperatures of up to 470oC on the planet’s surface.
Experts at Astrium and at Alcatel Alenia Space will use a variety of techniques to protect the electronics and scientific instruments from the extreme heat including a newly designed insulating multi-layer blanket whose top layer is likely to be made using ceramic-fibres. A radiator will release the heat from the probe’s interior into space, whose design makes it less sensitive to the thermal infrared radiation emitted by the planet’s surface. In addition the spacecraft will use special solar arrays capable of supplying power even when temperatures reach 250oC.
The combination of a conventional chemical propulsion system with an innovative ion propulsion system will provide the required thrust on BepiColombo’s long journey. Several swing-by manoeuvres are planned to reach Mercury. During these manoeuvres, BepiColombo will be accelerated using the gravity fields of the Moon, Earth and Venus. BepiColombo is scheduled to reach its destination in 2019 and enter into a polar orbit after two further swing-by manoeuvres at Mercury.
Scheduled to explore Mercury for at least 12 months, the spacecraft’s mission may be extended by a further year. To date, planetary researchers know very little about the hottest planet in our solar system. Most of the detailed data comes from NASA’s Mariner 10 spacecraft which performed three flybys in the seventies and was able to image part of the planet.