On September 3, 2026, the European Space Agency will attempt a complex operation: separating BepiColombo’s Mercury Transfer Module (MTM) after eight years of travel through the Solar System. The spacecraft will not enter Mercury’s orbit during the maneuver, but the separation marks a point of no return for a mission that has already endured nine planetary flybys and the Sun’s constant pull.
ESA’s control center in Darmstadt will broadcast the maneuver live, with separation scheduled for 14:00 CEST. Powered by solar-electric propulsion, the MTM has gradually slowed the spacecraft through gravity assists: one at Earth, two at Venus and six at Mercury. The six Mercury flybys took place in October 2021, June 2022, June 2023, September 2024, December 2024 and January 2025, information from ESA’s official mission page. After this final push, the scientific instruments will face Mercury’s harsh environment on their own. ESA has designated the MTM separation as the start of BepiColombo’s arrival phase at Mercury, one of the most complex orbital scenarios the agency has ever executed.
The tension will continue after the module’s release. Ground teams will wait for confirmation, with the first signal expected no earlier than 15:53 CEST. Until then, engineers will await a clean separation and confirmation that the systems are working, leaving the mission’s fate uncertain. Any problem at this stage could threaten years of work and major investment.
BepiColombo will not enter Mercury’s orbit on September 3. ESA’s timeline puts orbital insertion on November 21, 2026. The spacecraft will continue its approach using the chemical propulsion of the Mercury Planetary Orbiter (MPO), moving closer to the planet under its gravity. Only then will the two scientific orbiters, ESA’s MPO and JAXA’s Mio, begin their final orbits around Mercury.
Once in orbit, the sequence becomes more involved. The two orbiters will remain docked in a polar trajectory before the Japanese-built Mio is released in early December. The shield that has protected Mio from space will then be discarded. The MPO will descend further, aiming to reach its operational orbit by March 2027, with regular science operations scheduled to begin in April.
Reaching Mercury is difficult. The Sun’s gravity accelerates any spacecraft heading inward, making it easy to overshoot and difficult to stop. BepiColombo’s nine flybys were needed to reduce its speed and adjust its course without using too much fuel. The MTM’s ion engines, powered by solar panels and xenon, completed their last burn in June 2026, leaving the spacecraft on a ballistic path toward Mercury.
Mercury remains the least explored of the inner planets. Its surface and magnetic field hold clues about how rocky planets form. ESA’s MPO will study the planet’s crust, composition and interior, while Mio will focus on the magnetosphere and its interaction with the solar wind. The data could change what we know about planets close to the Sun.
The September maneuver will test engineering and international teamwork. The mission’s complexity, involving two agencies, two orbiters and a multi-stage arrival, shows the scale of the challenge. As the countdown begins, ESA is aiming for a precise operation that could set a new standard for space missions. If BepiColombo succeeds, it will open a new chapter in Mercury research and demonstrate how Europe and Japan can work together at the edge of the Solar System.
