BepiColombo Nearing Arrival: Transfer Module to Separate on 3 September 2026

The ESA/JAXA mission BepiColombo is entering one of the critical phases of its journey to the Sun’s nearest planet. On 3 September 2026 the separation of the Mercury Transfer Module (MTM) is planned. With this maneuver the arrival phase at Mercury officially begins. Orbital insertion is scheduled for November, and the separation of the two scientific orbiters is planned for December.

Schedule and procedure

In an online press conference on 31 August 2026, mission officials outlined the sequence: after the MTM separation, final trajectory adjustments and braking maneuvers will follow. In November, BepiColombo is to swing into orbit around Mercury. In December the European Mercury Planetary Orbiter (MPO) and the Japanese orbiter Mio (MMO) will separate to start their respective measurement programs.

Why the separation is critical

The MTM carried the two orbiters through interplanetary space, supplied power and executed course corrections. Before orbital insertion it must be jettisoned so that MPO and Mio can focus with their own propulsion and attitude-control systems on the capture and braking maneuvers. A clean separation protects instruments from unwanted forces and keeps orbital parameters within the intended window.

Particular challenges at the Sun’s nearest planet

Proximity to the Sun increases thermal loads and complicates navigation. To enter a Mercury orbit the spacecraft must shed energy rather than simply “falling in,” as is sometimes assumed. That requires a series of carefully timed maneuvers and strict thermal management.

Risks and precautions

Mission control relies on redundant communications paths, precisely defined time windows and precomputed contingency maneuvers in case telemetry data drop out during the separation sequence. All subsystems were tested in simulations using realistic telemetry profiles. Ground stations in Europe and Japan plan tightly scheduled contact sessions to implement short-notice trajectory corrections and software adjustments if needed.

Milestones toward scientific operations

After orbital insertion, MPO and Mio will fine-tune their orbits and configure their instruments. MPO will focus on Mercury’s surface, composition and internal structure. Mio will study the magnetosphere and plasma environment. A calibration and validation phase is planned before regular scientific operations begin.

Scientific expectations

Mercury is one of the least explored inner planets. BepiColombo aims to address open questions about its formation and evolution: the size and nature of its iron core, the role of early impacts, and the effects of intense solar radiation on the surface and exosphere. Higher spatial resolution and complementary measurement techniques promise new insights.

International cooperation

BepiColombo is a joint mission of ESA and JAXA. Teams in Europe and Japan coordinate telemetry, operation planning and scientific priorities. The close cooperation increases complexity but creates synergies through parallel observations from different perspectives.

Outlook

The MTM separation marks the decision point for the mission’s next course. If the maneuver proceeds as planned, BepiColombo will prepare for orbital insertion and set the stage for scientific operations by the end of the year.