This animation shows the Interplanetary Cruise Phase (ICP) of the BepiColombo mission.
After the mission's lunar gravity assist, an interplanetary cruise phase starts that will last nearly six years. The Mercury Composite Spacecraft will use both its solar electric propulsion system and a series of five planetary flybys (respectively Earth, Venus 2x, Mercury 2x) to reach the Solar System's innermost planet.
The solar electric propulsion system is located in the Mercury Transfer Module (MTM) and will be activated during selected parts of the spacecraft's trajectory. The thrust arcs, where the ion engines are on, are indicated with red in this animation that shows the spacecraft's cruise through the inner Solar System as well as the planetary orbits.
During the first thrust arcs, when still outside the orbit of Venus, the spacecraft will be accelerated by thrusting in the direction opposite to the spacecraft's direction of motion. Only one of the four ion engines will be fired at these times, due to limited available power from the solar panels when outside Venus's orbit.
During the remainder of the interplanetary cruise phase, after completion of the two Venus flybys, the ion engines will be firing in the same direction that the spacecraft is travelling, to brake against the pull of the Sun's gravity and lower the heliocentric orbit. During these thrust arcs two ion engines will be used (with the second set of ion engines available for redundancy).
About two months before capture by Mercury, the Mercury Transfer Module (MTM) carrying the solar electrical propulsion and main chemical propulsion system is detached, leaving the two Mercury orbiters to be caught by the planet's gravity.