ESA Science & Technology - Mission Design and Deployment Sequence

The Mercury Composite Spacecraft (MCS) of the BepiColombo mission comprises the three main elements:

• Mercury Magnetospheric Orbiter (MMO - blue) surrounded by a Sunshield (yellow) up to Mercury orbit insertion
• Mercury Planetary Orbiter (MPO - green) with solar panel
• Mercury Transfer Module (MTM - grey) with two solar array wings

NECP – Near Earth Commissioning Phase
After launch into a geostationary transfer orbit, the MCS will be boosted to the phasing orbit using chemical propulsion. From here the composite spacecraft will be set on its interplanetary trajectory through a flyby of the Moon (bottom right).

Cruise
On its way to Mercury, the spacecraft must brake against the Sun's gravity, which increases with proximity to the Sun. BepiColombo will accomplish this by making clever use of the gravity of the Earth, Venus and Mercury itself and by using solar electric propulsion (on the MTM). At the end of the interplanetary cruise phase, about two months before capture by Mercury, the MTM detaches.

Arrival at Mercury
When approaching Mercury, the spacecraft will use the planet's gravity plus conventional rocket engines (on the MPO) to insert itself into a polar orbit. A special Weak Stability Boundary Capturing technique is employed. This gives flexibility and is more robust against failures compared to using the more traditional "big kick" approach (single burn capture).

The MMO will be released into its operational orbit, then the Sunshield and the MMO interface structure will be separated while the MPO uses its own chemical propulsion to enter a lower orbit.