Come face-to-face with a full-size engineering model of BepiColombo, the European Space Agency’s first ever spacecraft to explore Mercury at the Science Museum in London. BepiColombo is Europe’s first mission to Mercury. It will set off in 2018 on a journey to the smallest and least explored terrestrial planet in our Solar System.

Most of ESA’s previous interplanetary missions have been to relatively cold parts of the Solar System. BepiColombo will be the Agency’s first experience of sending a planetary probe close to the Sun. Mercury is the smallest and innermost planet in the Solar System. Only two spacecraft have ever visited Mercury: Mariner 10 flew by in 1974/1975; and MESSENGER, launched in 2004, orbited Mercury over 4,000 times in four years before exhausting its fuel and crashing into the planet’s surface on April 30, 2015.
Albeit the nearest planet to the Sun it is often considered as the most boring one. But Mercury has an important role in showing us how planets form. Mercury, Venus, Earth and Mars make up the family of terrestrial planets; each one carrying essential information to trace the history of the whole group.

The knowledge about how they originated and evolved, is key to understanding how conditions supporting life arose in the Solar System, and possibly elsewhere. As long as Earth-like planets orbiting other stars remain inaccessible to astronomers, the Solar System is the only laboratory where scientists can test models applicable to other planetary systems. Exploring Mercury is therefore fundamental to answering important astrophysical and philosophical questions such as ‘Are Earth-like planets common in the Galaxy?’

A European mission to Mercury was first proposed in May 1993. Although an assessment showed it to be too costly for a medium-size mission, ESA made a Mercury orbiter one of its three new cornerstone missions when the Horizon 2000 science programme was extended in 1994. BepiColombo will provide the best understanding of Mercury to date. It consists of two individual orbiters: the Mercury Planetary Orbiter (MPO) to map the planet, and the Mercury Magnetospheric Orbiter (MMO) to investigate its magnetosphere.

In the course of testing, the model was subjected to extremes of temperatures ranging from -190°C to 350°C, recreating the conditions the spacecraft will face when in shade and when in the illuminated face of Mercury. The BepiColombo STM has been loaned to the Science Museum by the European Space Agency (ESA) and was developed and build for ESA by Airbus, the mission’s prime industrial contractor.
When it arrives at Mercury in late 2025, it will endure temperatures in excess of 350 °C and gather data during its 1 year nominal mission, with a possible 1-year extension. The mission comprises two spacecraft: the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (MMO). BepiColombo is a joint mission between ESA and the Japan Aerospace Exploration Agency (JAXA), executed under ESA leadership.

In May 2018 the spacecraft of the BepiColombo mission to Mercury have arrived safely at Europe’s Spaceport in Kourou, French Guiana, marking the start of six months of preparation to ready the craft for launch.

The joint ESA-JAXA mission, which comprises three spacecraft modules and a sunshield, were transported from their home base in ESA’s technical heart in the Netherlands by road to Amsterdam Schiphol airport. They were flown to Kourou, French Guiana, on a series of four Antonov cargo aircraft over the last two weeks. They were accompanied by approximately 40 containers of essential ground-support equipment, hardware, and other loose items needed for the pre-launch testing and configuring the spacecraft at the launch facility. Another 15 containers travelled by sea.

Diana Wehmeier
MISSION TO MERCURY: BepiColombo in the Science Museum London

Once the spacecraft arrived, their containers were opened and the modules lifted out on their respective multi-purpose trolleys for inspection, to confirm that no problems arose from the transport. The spacecraft were also switched on and batteries tested, and the various mechanical and electrical ground support systems installed.

Over the next six months activities will include attaching the solar wings to the modules and their deployment mechanisms tested, dressing the spacecraft in protective insulation to prepare for the harsh space environment and extreme temperatures they will experience operating close to the Sun, installing the sunshield, conducting pressure tests, fuelling, and connecting the three spacecraft together.

The ESA Mercury Planetary Orbiter and the JAXA Mercury Magnetospheric Orbiter will travel together to the innermost planet, carried by ESA’s Mercury Transfer Module. The final weeks will see the completed spacecraft stack inside the Ariane 5 rocket fairing, and preparing the launch vehicle itself, ready to blast the mission on a seven-year journey around the inner Solar System to reach Mercury and start investigating its mysteries.

The upcoming launch window opens on 5 October and closes 29 November 2018.

One of ESA’s cornerstone missions, it will study and understand the composition, geophysics, atmosphere, magnetosphere and history of Mercury, the least explored planet in the inner Solar System.
BepiColombo’s mission is especially challenging because Mercury’s orbit is so close to our star. The planet is hard to observe from a distance, because the Sun is so bright. Furthermore, it is difficult to reach because a spacecraft must lose a lot of energy to ‘fall’ towards the planet from the Earth. The Sun’s enormous gravity presents a challenge in placing a spacecraft into a stable orbit around Mercury.Among several investigations, BepiColombo will make a complete map of Mercury at different wavelengths. It will chart the planet’s mineralogy and elemental composition, determine whether the interior of the planet is molten or not, and investigate the extent and origin of Mercury’s magnetic field.

Several launch methods have been extensively studied. In the selected scenario, BepiColombo will use the gravity of Earth, Venus and Mercury in combination with the thrust provided by solar-electric propulsion (SEP). During the voyage to Mercury, the two orbiters and a transfer module, consisting of electric propulsion and traditional chemical rocket units, will form one single composite spacecraft.

When approaching Mercury in late 2025, the transfer module will be separated and the composite spacecraft will use rocket engines and a technique called ‘weak stability boundary capture’ 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 own operational orbit. Observations from orbit will be taken for at least one Earth year with the possibility of an extension.

Diana Wehmeier


Visit the Tomorrow’s World gallery at the Science Museum London for a close-up view of this integral part of a space mission’s development programme.

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