This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Launched on Oct. 20, 2018, the joint ESA/JAXA BepiColombo mission has traveled for almost eight years, using a carefully planned but eventful sequence of planetary flybys and solar-electric propulsion to gradually approach its destination, Mercury. The mission is now entering the final stage of its journey to the smallest and innermost planet of our solar system.
The BepiColombo spacecraft consists of the Mercury Transfer Module (MTM) and two orbiters: ESA's Mercury Planetary Orbiter (MPO) and JAXA's Mercury Magnetospheric Orbiter (Mio). The spacecraft are flying to Mercury together as a coupled system, but once there, they will be placed into separate orbits. Following the first separation maneuvers of the MTM from Mio and MPO, preparations are underway for the spacecraft's arrival at Mercury and the start of its scientific mission in 2027.
Aboard the space probe is an instrument designed and built at the Physics Institute of the University of Bern: the laser altimeter BELA—the heaviest instrument on the MPO probe. On Sept. 14, 2026, the instrument team successfully activated BELA's laser for the first time in space and for the first time since 2017. On Sept. 14, 2016, the laser altimeter BELA 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 toward the start of BepiColombo's scientific mission. BELA was developed by an international consortium under the leadership of the University of Bern and the German Aerospace Center (DLR), in cooperation with the Max Planck Institute for Solar System Research and the Institute of Astrophysics of Andalusia (IAA-CSIC). The aim is to measure the shape, topography and morphology of Mercury's surface.
"With BELA, we will be able to create a three-dimensional representation of Mercury with unprecedented accuracy," explains Antoine Pommerol from the Space Research and Planetary Sciences Division at the Physics Institute of the University of Bern, co-principal investigator for BELA. The activation of BELA followed a carefully controlled sequence. First, the team commanded the laser to emit a 10-second burst.
During this initial test, more than 100 ultrashort pulses of infrared light were sent toward open space from the spacecraft, which is roughly 200 million kilometers (124 million miles) away from Earth. Pommerol explains, "The laser pulses were only sent toward open space this time, not yet toward Mercury. But they could still be characterized by the instrument, providing crucial data on the health of the laser system after eight years in space and nine years since its last firing.
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