After nearly a decade and nine planetary flybys, BepiColombo is about to attempt a high-risk maneuver: separating its transfer module before the final approach to Mercury. The mission’s science work won’t start until 2027, but the next steps are crucial.
On September 3, 2026, the European Space Agency will attempt a complex operation: separating BepiColombo’s Mercury Transfer Module (MTM) after eight years traveling through the Solar System. This isn’t the moment the spacecraft enters Mercury’s orbit, but it marks a point where there’s no turning back for a mission that has already survived 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. The MTM, powered by solar-electric propulsion, has been responsible for gradually slowing the spacecraft through a series of gravity assists—one at Earth, two at Venus, and six at Mercury. After this final push, the scientific instruments will be left to face Mercury’s harsh environment on their own.
ESA has officially designated the MTM separation as the beginning of BepiColombo's arrival phase at Mercury, marking one of the most complex orbital scenarios the agency has ever executed.
The tension doesn’t end with the module’s release. Ground teams will wait for confirmation, with the first signal expected no earlier than 15:53 CEST. Until then, the mission’s fate will be uncertain, as engineers hope for a clean separation and working systems. Any problem at this stage could threaten years of work and major investment.
BepiColombo will not enter Mercury’s orbit on September 3. According to ESA’s timeline, orbital insertion is planned for November 21, 2026. The spacecraft will continue its approach using the chemical propulsion of the Mercury Planetary Orbiter (MPO), moving closer to the planet’s 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 gets even more involved. The two orbiters will stay 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 for its operational orbit by March 2027, with regular science operations set to begin in April.
ESA’s official mission page lists six Mercury flybys during BepiColombo’s cruise phase: October 2021, June 2022, June 2023, September 2024, December 2024, and January 2025. These gravity assists were essential for slowing the spacecraft and setting up its final approach.
Reaching Mercury is difficult. The Sun’s gravity speeds up any spacecraft heading inward, making it easy to overshoot and hard to stop. BepiColombo’s nine flybys were necessary, each one reducing speed and adjusting course to avoid burning too much fuel. The MTM’s ion engines, powered by solar panels and xenon, finished their last burn in June 2026, leaving the spacecraft on a ballistic path toward Mercury.
Mercury is still 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.
For now, the September maneuver is a test of engineering and international teamwork. The mission’s complexity—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 for Mercury research and show how Europe and Japan can work together at the edge of the Solar System.
