Ariane 5 launches BepiColombo to Mercury


Final preparations are underway for the launch of a joint-European and Japanese mission to Mercury, the closest planet to the Sun.

Engineers worked throughout the day in ESOC's Main Control Room simulating BepiColombo's launch, maintaining data and voice contact with their counterparts at Europe's Spaceport in Kourou, French Guiana, and at the ground stations that will support BepiColombo's departure.

BepiColumbo's ion thrusters will be firing for 4.5 years, more than half the journey time.

The spacecraft will take seven years to reach the planet closest to the sun. Over the course of such a mission, a spacecraft must build up energy to resist the Sun's gravitational pull and slide into orbit around Mercury.

Before beginning its orbit of Mercury in 2025, the spacecraft will flyby Earth in 2020, flyby Venus in 2020 and 2021, and then perform six different flybys of Mercury before making it into orbit.

One might think it's a relatively easy thing to reach Mercury, the innermost planet in the Solar System. BepiColombo comprises two spacecraft, the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (MMO), each loaded with instruments that will measure the planet's magnetic field, its chemical makeup, how it feels the Sun's gravity, and more.

The mission will undertake a seven year cruise to Mercury, using a combination of solar electric propulsion and nine gravity assist flybys at Earth, Venus and Mercury.

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"BepiColombo will build on the discoveries and questions raised by NASA's Messenger mission to provide the best understanding of Mercury and Solar System evolution to date, which in turn will be essential for understanding how planets orbiting close to their stars in exoplanet systems form and evolve, too".

It's hoped their parallel observations can finally resolve some of the many puzzles about the hot, oddball planet. Originally called the Mercury Magnetospheric Orbiter, MMO, in June it was awarded the name Mio, which in Japanese carries connotations of safe navigation.

ESA member states nearly cancelled BepiColombo after the mission, which began in 2000, grew too large to fit in a Soyuz rocket, requiring a more expensive Ariane 5 to continue. One of the orbiters, known as the Mercury Planetary Orbiter, will make a wide-spectrum survey of the planet using a suite of 11 instruments, including cameras, spectrometers, a radiometer and a laser altimeter. Some other mysterious features of the planet that BepiColombo could help us better understand include why it appears to have shrunk over time and how it generates its own magnetic field despite spinning very slowly on its axis. BepiColombo is set to approach Mercury in December 2025, the mission will last until May 2027.

That means that some places on Mercury don't see sunlight for 2 Mercury years, some are in perpetual "high noon" for weeks at a time, and others occasionally see the Sun reverse direction just after rising or just before setting.

It's estimated the costs borne by the European Space Agency and the Japanese space agency amount to about €1.65bn.

Even if BepiColombo only partially fulfills its objectives, the knowledge that researchers gained in designing and launching the spacecraft will be applied to future missions. It was he who proposed the NASA trajectory that allowed Mariner 10 to fly by the planet.

This is only the third mission to Mercury, following NASA's Mariner 10 in 1974-1975 and Messenger in 2011-2015.