It’s not easy getting to Mercury. At its closest, the innermost planet of the Solar System might be only 77 million km away from Earth. It will, however, require more energy for the European-Japanese spacecraft BepiColombo to get to its destination than it would reaching the dwarf planet Pluto, orbiting between 4.4 and 7.3 billion km away from the Sun.
The spacecraft’s cruise through the inner Solar System takes seven years before its two orbiters, ESA’s Mercury Planetary Orbiter and the Mercury Magnetospheric Orbiter of the Japanese Aerospace Exploration Agency, can be placed into the correct orbits around the scorched rocky planet. In comparison, Solar Orbiter, which heads even closer to the Sun, within the orbit of Mercury, needs just under two years to reach its destination.
Why does it take so long for BepiColombo then? Travelling from Earth towards the Sun, BepiColombo needs to constantly brake against the gravitational pull of the massive star in order to be able to reach Mercury with just the right velocity to enter a stable orbit around the planet. To slow down, BepiColombo uses a combination of the solar electric propulsion system aboard the Mercury Transfer Module, one of the components of the mission, and overall nine gravity-assist flyby manoeuvres at planets Earth, Venus and Mercury.
The interactive ‘Where is Bepi’ tool below allows you to explore BepiColombo’s trajectory, including its flybys, and follow the position of the spacecraft on every single day of its journey.