BepiColombo — Investigating Mercury's mysteries

BepiColombo | BELA & STROFIO

BepiColombo is Europe and Japan's first mission to Mercury, and the second and most complex mission ever to orbit the planet. A joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA), BepiColombo will investigate the small desert world of Mercury, which is the innermost and least explored planet in the inner Solar System. The mission is comprised of two science orbiters – the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (Mio) – packed with scientific instruments to thoroughly study the planet. On board of MPO are two instruments developed at the University of Bern: the BepiColombo Laser Altimeter (BELA) and STROFIO (sTart from a ROtating Field mass spectrOmeter), which will map the planets surface and analyze its exosphere, respectively.

UPCOMING MISSION HIGHLIGHTS

21 November 2026

11 weeks after the begin of BepiColombo's Mercury Arrival Phase and separation from the Mercury Transfer Module (MTM), MPO and Mio—still joined together—will be captured by Mercury's gravity into a polar orbit around the planet.

Once captured by Mercury's gravity, the two orbiters will remain joined 2.5 weeks before the final arrival steps require MPO to release Mio into its own orbit around the planet.

LATEST MISSION HIGHLIGHTS

14 September 2026

Following the successful separation of the Mercury Transfer Module (MTM) from the two orbiters, the mission reached another important milestone: the laser of the BELA altimeter was successfully activated for the first time in space.

On board of BepiColombo's Mercury Planetary Orbiter (MPO) is an instrument which was designed and built at the Physics Institute of the University of Bern: the laser altimeter BELA – the heaviest instrument on the MPO probe. On 14 September 2016, the laser altimeter BELA had left Bern for ESA’s European Space Research and Technology Centre ESTEC to be integrated onto the MPO spacecraft. Ten years later to the day, the instrument team from the University of Bern and the German Aerospace Center (DLR) Berlin fully activated the BELA laser altimeter for the first time since the spacecraft began its journey – a crucial step towards the start of BepiColombo’s scientific mission. Read the full press release of the University of Bern here.

03 September 2026

BepiColombo began its Mercury Arrival Phase. The Mercury Transfer Module (MTM) separated from its two science orbiters MPO and Mio. This was the first critical stage after the eight-year journey BepiColombo has successfully made to Mercury.

The European Space Agency (ESA) livestreamed the separation of the MTM on their YouTube account on September 03, starting 13:45 CEST. You can read about the successful separation on the ESA website here.

ESA Livestream: BepiColombo's Mercury arrival begins

BepiColombo Footage from the Mercury Transfer Module

BepiColombo at the University of Bern

The contributions of the Physics Institute at the University of Bern are both located on the Mercury Planetary Orbiter (MPO). The BepiColombo Laser Altimeter (BELA) forms an integral part of a larger geodesy and geophysics package, incorporating radio science and stereo imaging. It was developed by the Planetary Imaging Group (PIG) under the leaderhsip of Prof. em. Dr. Nicolas Thomas, in collaboration with the German Aerospace Center (DLR). Current instrument PI in Bern is PD Dr. Antoine Pommerol. Development of the mass spectrometer STROFIO, part of the larger SERENA science experiment, was led by Prof. em. Dr. Peter Wurz. Nicolas Thomas and Peter Wurz were both also part of ESA's science advisory group which designed the mission.

BELA

BELA is one of the most important and most sensitive experiments on board the MPO. Its aim is to measure the shape, topography and morphology of the surface of Mercury in order to create a digital terrain model that allows quantitative exploration of the geology, the tectonics, and the age of the planet's surface.

STROFIO

STROFIO is an innovative mass spectrometer and one of four sensors of the SERENA experiment on board the MPO. It was specifically built for Mercury's atmosphere and MPO's orbit, where it will in-situ record the density of low-energy neutral particles within the exosphere and analyze its chemical composition.

More about the mission

BepiColombo is the second mission to orbit Mercury and also the most complex to do so. More than that, it is the first European mission to Mercury and also the first mission to the planet made up of two science orbiters, which enables unique and complementary measurements.

BepiColombo's aim is to uncover the mysteries of the innermost and until now least explored planet of the inner Solar System. Throughout its lifetime, the mission is concerned with i) the origin and evolution of a planet close to its parent star, ii) the planet's interior structure and composition, iii) the characteristics and origin of its internal magnetic field, iv) the surface processes, such as cratering, tectonics, polar deposits and volcanism, v) the structure, composition, origin and dynamics of Mercury's exosphere, vi) the structure and dynamics of Mercury's magnetosphere, and vii) Einstein's Theory of General Relativity (by making precise measurements of the spacecraft's orbit and position).