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En route to Mercury

The BepiColombo space mission was launched on the night of October 19-20, 2018 aboard an Ariane 5 vehicle from the spaceport in Kourou, Guiana. The Plasma Physics Laboratory is responsible for two of the instruments on board the MIO probe set to explore the magnetosphere of Mercury.

Launched into space aboard an Ariane 5 vehicle on Saturday October 20 from the spaceport in Kourou, Guiana, the two orbiters of the BepiColombo mission are on their way to explore planet Mercury. They will reach the planet closest to the Sun after a journey of seven years through space. The objective is to map and study its surface, its thin atmosphere  (or exosphere) and its magnetosphere.

The first orbiter of the mission, MPO, is a European Space Agency (ESA) spacecraft designed to map the planet’s surface, its internal structure, and its exosphere. The second, Mio (formerly MMO: Mercury Magnetospheric Orbiter), is under the responsibility of JAXA, the Japan Aerospace Exploration Agency, and its focus is Mercury’s magnetosphere and its interaction with the solar wind. Two research teams at the Plasma Physics Laboratory (LPP, a joint CNRS/ École polytechnique/Sorbonne Université/Université Paris-Sud/Observatoire de Paris research unit) were involved in the design and manufacture of instruments on Mio.

Mercury’s magnetosphere

Like Earth, Mercury has a magnetic shield, a magnetosphere, created by the planet’s magnetic field. This magnetosphere forms a gigantic “bubble of plasma” around the planet, a mix of ions and electrons, the composition and properties of which remain to be discovered.

Mercury’s magnetic field is much weaker than Earth’s field and does not protect it as well from solar winds. Scientists are hoping that observations of a magnetosphere whose conditions are different from those around Earth and which is in great proximity to the sun and to its activity, will improve our understanding of plasmas in space and around magnetized planets.

Two LPP instruments

Mio carries as payload two LPP instruments. First, the MSA ion spectrometer  that will measure the composition of the bubble of plasma around Mercury. The optical part of this instrument, placed under the responsibility of LPP, was developed at the laboratory, with contributions from Japanese and German laboratories for the electronics.

The second instrument, a Dual-B Search Coil (DB-SC) is a magnetometer  that will measure magnetic waves, meaning the fluctuations of the magnetic field in Mercury’s magnetosphere. The distinctive feature of this magnetometer is its capacity to measure both low and high frequencies.

Seven LPP researchers traveled to Guiana to attend the launch of BepiColombo on October 20 and the entire Space Plasmas research team will be closely monitoring the seven year cruise (including several flybys of Earth, Venus and Mercury) before the orbiters separate and slip into orbit around Mercury in December 2025.

> Find out more about the mass spectrum analyzer: spectromètre de masse ionique du LPP

> Find out more about the magnetometer: magnétomètre « Search coil » du LPP

Bepi-Colombo already deployed its solar panels in space.