The MPO will circle the planet along an orbit ranging between 400 and 1500 kilometres above the surface. The MMO orbit ranges between 400 and 12 000 kilometres above the surface. The inclination and the eccentricity of these orbits are optimised for the study of the planet and of its magnetosphere in the very high temperature environment around Mercury.

The MPO will circle the planet along an orbit ranging between 400 and 1500 kilometres distance from the surface. The MMO orbit ranges between 400 and 12000 kilometres from the surface. The inclination and the eccentricity of these orbits are optimised for the study of the planet and of its magnetosphere in the very-high-temperature environment around Mercury.

Credits: ESA - image by C.Carreau

For its journey to Mercury BepiColombo will cleverly use the gravity of the Moon, Earth, Venus and Mercury itself in combination with the thrust provided by solar-electric propulsion (SEP). During the voyage to Mercury, the two orbiters and transfer module, consisting of solar-electric propulsion and chemical propulsion units, will form one single composite spacecraft.

On approach to Mercury, the transfer module will separate and the composite spacecraft use conventional rocket engines and the so-called 'weak stability boundary capture technique' to bring it into polar orbit around the planet. When the MMO orbit is reached, the MPO will separate and lower its altitude to its operational orbit by chemical propulsion. Scientific investigations will go on for at least one Earth year (four Mercury orbits around the Sun).

Credits: ESA - image by C.Carreau

The transfer module, provided with a solar-electric propulsion system, will carry the two spacecraft up to Mercury’s gravitational sphere of influence, about 100 000 kilometres from the planet. Here, the spacecraft will use the planet's gravity plus conventional rocket engines to insert itself into a polar orbit that will be gradually reduced until the MMO operational orbit is reached. Here, the sunshield and the MMO interface structure will separate while the chemical propulsion system will bring the MPO to its lower operational orbit.

Credits: ESA - C.Carreau

The transfer module is provided with solar-electric propulsion and chemical propulsion units. The former will be used during the cruise to destination; the latter will be used after launch to boost up the orbit to the Moon's altitude for the planned lunar gravity-assist.

Credits: Astrium

Visible in the launcher fairing is the BepiColombo ‘stack’, consisting of the Mercury Planetary Orbiter (MPO), the Mercury Magnetospheric Orbiter (MMO), and the transfer module, all mounted on top of Fregat.

Credits: Astrium

BepiColombo will help reveal information on the composition and history of Mercury, and the history and formation of the inner planets in general, including Earth.

Credits: EADS Astrium