BepiColombo will be only the third spacecraft to visit Mercury in the history of space exploration. Mercury’s harsh environment makes it a particularly challenging mission. The spacecraft will have to endure intense sunlight and temperatures up to 350°C while gathering data.

This joint venture between Europe and Japan is an ESA ‘Cornerstone’ mission. It will help our understanding of the formation of the Solar System and its inner rocky planets, including Earth.

The mission will build on the experience gained in using electric propulsion on the SMART-1 mission. BepiColombo’s journey will also be helped by the gravity of the Moon, Earth and Venus during fly-bys to help it on its way to Mercury. It is due to arrive at the planet in 2019.

Mission facts

• Mercury is the second smallest planet in the Solar System, larger only than Pluto (if you count Pluto as a planet) and not much bigger than our own Moon.
  
  
• The surface is pock-marked with enormous craters caused by meteorites smashing into the planet’s surface in the early stages of the Solar System’s evolution some four billion years ago.
  
  
• Although Mercury is only a third the size of Earth, it is almost as dense.
  
  
• Scientists believe Mercury’s high density can be put down to the planet having a massive iron core.
  
  
• The first mission to Mercury was NASA's Mariner 10 in 1974.
  
  
• NASA's Mercury Messenger is currently on its way to Mercury and will arrive in 2011.
  
  
• BepiColombo is named after Giuseppe ‘Bepi’ Colombo (1920-1984), a scientist who studied Mercury's orbital motion in detail as well as orbits and interplanetary travel in general.
  
  
• It will take the BepiColombo spacecraft six years to reach its destination.
  
  
• Although the temperature on Mercury can go as high as 462°C, the side of the planet facing away from the Sun is always very cold.
  
  
• One of the key objectives for BepiColombo is to find out whether there is ice on the cold side of the planet.

Technology

BepiColombo will consist of three sections: a Mercury Transfer Module (MTM) – designed to get the spacecraft to the planet – and two orbiters: the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (MMO).

Astrium Limited in the UK is responsible for the entire structure of the spacecraft.

ESA is responsible for the larger MPO. Its 11 scientific instruments will study Mercury from a low-polar-orbit.

UK space scientists, led by the University of Leicester, will develop one of the key instruments on board BepiColombo: MIXS (Mercury Imaging X-ray Spectrometer). MIXS will be used to help determine the composition of the planet’s surface.

MIXS will measure fluorescent X-rays that originate from the Sun and are reflected off the planet’s surface. Fluorescent X-ray measurements can be used to identify chemical elements while measurements at infrared wavelengths can be used to determine mineral composition.

Japan is developing the MMO. This will have five science instruments on board designed to examine Mercury’s magnetic field and magnetosphere – the magnetic ‘bubble’ surrounding a planet. Mercury intrigues scientists because it is hard to understand why such a small planet can have a magnetic field at all.

Once clear of Earth, BepiColombo will make its way to Mercury with an ion engine. This employs solar panels to generate electricity which is used to produce charged particles from xenon gas. A beam of these charged particles, or ions, is then expelled from the spacecraft. The engine will be used to slow the spacecraft down so that it can eventually be captured by the gravity of Mercury.

UK involvement

BepiColombo has significant UK involvement. Much of the spacecraft will be built in Britain in partnership with several UK science teams.

Astrium Limited has been appointed as the prime contractor to build the European components. In the UK, the company will provide all the spacecraft structures as well as the electrical and chemical propulsion systems for the MTM, the chemical propulsion system for the MPO (which will be the first dual mode propulsion system designed and built in Europe) and the systems which will separate the spacecraft modules on arrival at Mercury.

Scientists from the University of Leicester are leading work on the MIXS instrument. Researchers from STFC Rutherford Appleton Laboratory (RAL), the University of Lancaster, Open University and UCL's Mullard Space Science Laboratory are also involved in many aspects of the mission.