BepiColombo : Separation of the MTM Transfer Module After an 8-Year Journey

BepiColombo : Another Decisive Step Toward Mercury

Thursday, September 3, 2026, will go down as a major milestone in the exploration of the Solar System. Eight years after the probe’s launch from Kourou, the MTM (Mercury Transfer Module), which carried the two scientific probes, MPO and Mio, separated from MPO, to which it had been attached since assembly.

The separation took place at 2:00 p.m. Paris time.

The MTM had no means of communicating directly with Earth. Engineers at the ESA operations center in Darmstadt, Germany, were therefore waiting for the first signal transmitted by the MPO to confirm the successful separation of the two spacecraft at approximately 3:53 p.m.

**Direct depuis l’European Space Operations Centre (ESOC) de l’ESA à Darmstadt, Allemagne, sur la chaîne Youtube de l’ESA.**

Crédit : ESA Standard Licence

BepiColombo at a Glance
BepiColombo is the first European mission to Mercury, conducted jointly by ESA and JAXA. Launched in 2018, it carries two scientific probes :

ESA’s Mercury Planetary Orbiter (MPO)
and JAXA’s Mercury Magnetospheric Orbiter (Mio).

These probes will study Mercury’s surface, internal structure, magnetic field, and environment. The European Mercury Transfer Module (MTM) successfully transported them to Mercury. After an eight-year journey, the mission is scheduled to reach the planet in November 2026, with scientific operations set to begin in April 2027.

A historic moment witnessed from Leuven, Belgium

Scientists from the Paris Observatory - PSL who are studying the planet Mercury had gathered at the Catholic University of Leuven (KU Leuven, Belgium) for the Mercury 2026 conference. On the afternoon of September 3, tension and excitement ran high in the historic conference hall where live coverage of the event was being projected.

Signal confirmant la séparation réussie du Mercury Transfer Module (MTM), après près de huit années de voyage. Le MTM a désormais laissé les deux orbiteurs scientifiques, MPO (European Space Agency - ESA) et Mio (JAXA : Japan Aerospace Exploration Agency), poursuivre leur approche de Mercure.

Crédit : Alain Doressoundiram / Observatoire de Paris - PSL / LIRA

When the image from the signal appeared on the wall (a few minutes ahead of schedule), applause rang out in the room, along with a huge sense of relief : most of the researchers present have been working on BepiColombo for over ten years ! Some have even been following the project since its first presentation to ESA... in 2004 !

Two Spacecraft to Explore an Extraordinary Planet

This is the first time in history that two spacecraft will be deployed simultaneously around another planet—in this case, one of the most difficult to reach : Mercury.

The BepiColombo mission has already broken several records, including the closest flyby of a planetary surface at an altitude of 164 kilometers during the 4^th flyby of Mercury on September 4, 2024.

LIRA at the Heart of the Mission

The LIRA at the Paris Observatory - PSL is responsible for two instruments, one on each of the two probes :

SORBET (PI : K. Issautier), the high-frequency radio receiver of the “Plasma Wave Instrument” suite aboard Mio (the Japanese probe) ;
and VIHI (Co-PI : A. Doressoundiram), the spectroradiometer of the “SIMBIO-SYS” suite aboard MPO (the European satellite).

These two instrumental contributions bring together about ten researchers from LIRA, and in particular, four doctoral theses are currently underway to prepare for the analysis of the scientific data, which is expected to arrive in the spring of 2027.

Next Steps

**Principales étapes de l’arrivée sur Mercure.**

Crédit : ESA

The mission continues its gradual approach to Mercury :

November 21, 2026 : insertion into orbit around Mercury
December 9, 2026 : Separation of MPO and Mio
December 16, 2026 : Jettisoning of the heat shield protecting Mio
March 10, 2027 : MPO reaches its final scientific orbit
April 6, 2027 : Start of scientific operations