BepiColombo’s Mercury arrival begins – full replay

Meta Title: BepiColombo’s Mercury Arrival Begins With Transfer Module Separation

Meta Description: ESA and JAXA’s BepiColombo mission begins its final Mercury arrival sequence with the planned separation of its Mercury Transfer Module on 3 September 2026.

URL Slug: bepicolombo-mercury-arrival-transfer-module-separation

Excerpt: BepiColombo’s long journey to Mercury is entering its most demanding phase. The planned separation of its Mercury Transfer Module marks the start of a carefully choreographed arrival campaign ahead of orbital operations around the Solar System’s innermost planet.

## BepiColombo Starts Its Final Approach to Mercury

The ESA-JAXA BepiColombo mission is preparing to take a major step toward its long-awaited arrival at Mercury. On 3 September 2026, the spacecraft’s Mercury Transfer Module (MTM) is scheduled to separate from the two science orbiters it has carried through the inner Solar System for years.

The event marks the beginning of a complex final-arrival sequence rather than the moment BepiColombo enters Mercury orbit. The mission is expected to complete its orbital insertion phase later in 2026, after a series of operations designed to slow, position and configure the spacecraft for science at the Solar System’s smallest and innermost planet.

ESA described the separation in a livestream programme from its European Space Operations Centre (ESOC) in Darmstadt, Germany. The broadcast was scheduled to include mission-control coverage, expert commentary and the first expected signal confirming the spacecraft’s status after the modules separated.

Because the source item is a scheduled ESA video listing dated 3 September 2026, it does not independently confirm the outcome of the manoeuvre. The key facts known in advance are the planned separation time, the role of the MTM and the mission’s broader arrival plan. Confirmation of a successful separation and spacecraft health check would depend on telemetry received by ground teams after the event.

## What Is the Mercury Transfer Module?

BepiColombo is not a single spacecraft in the conventional sense. It launched in October 2018 as a composite stack of several elements, each with a distinct job.

The Mercury Transfer Module has provided propulsion during the long cruise phase. Its solar-electric propulsion system uses ion thrusters, which accelerate electrically charged particles to generate a gentle but highly efficient continuous thrust. This approach is especially useful for a mission that must make major changes to its orbit around the Sun while carrying two orbiters toward Mercury.

The MTM’s work is largely complete once the mission reaches its final approach. It is not designed to enter Mercury orbit or conduct the main science mission. Instead, the two orbiters it delivered are intended to continue on:

– **ESA’s Mercury Planetary Orbiter (MPO),** focused primarily on studying Mercury’s surface, interior and environment.
– **JAXA’s Mercury Magnetospheric Orbiter (Mio),** designed to investigate Mercury’s magnetic field and the charged-particle environment around the planet.

Separating the MTM is therefore a necessary handover from interplanetary transport to planetary exploration.

## Why Getting to Mercury Is So Difficult

Mercury may appear relatively close to Earth on a Solar System diagram, but it is one of the most challenging destinations for a robotic mission.

The fundamental problem is the Sun’s gravity. Any spacecraft travelling inward from Earth’s orbit naturally accelerates as it falls deeper into the Sun’s gravitational field. To enter orbit around Mercury, a probe must shed a great deal of solar-orbital energy. Simply pointing a spacecraft toward the planet would cause it to fly past at excessive speed.

BepiColombo has addressed that problem through a lengthy sequence of gravity-assist flybys. These encounters have used the gravity of Earth, Venus and Mercury itself to reshape the spacecraft’s path and gradually reduce the energy required for final capture.

The mission’s trajectory has included one Earth flyby, two Venus flybys and multiple Mercury flybys. Each close approach required careful navigation and timing. Together with the MTM’s electric propulsion, those flybys have helped guide BepiColombo toward an orbit compatible with Mercury arrival.

This long route explains why the mission launched in 2018 but is not expected to begin its dedicated science-orbit phase until late 2026.

## Separation Is Only the Beginning of the Arrival Campaign

The MTM separation is an important milestone, but it is not the only technically demanding moment ahead.

After separation, the remaining spacecraft configuration must be prepared for the conditions near Mercury. The planet circles close to the Sun, where sunlight is far more intense than it is at Earth. Thermal control, spacecraft orientation and power management are central concerns throughout the mission.

BepiColombo also needs to transition from its cruise configuration to arrangements suitable for orbital operations. The process includes planned manoeuvres, communications checks and eventually the release of the two science orbiters into their intended trajectories around Mercury.

ESA and JAXA have previously outlined plans for Mercury orbit insertion in December 2026. The final sequence is expected to involve the separation of the MPO and Mio spacecraft, allowing them to operate in complementary orbits. Their separate perspectives should help scientists link conditions at Mercury’s surface with processes in its magnetic environment.

Until agencies publish post-event updates, however, it is important to distinguish the planned timeline from confirmed results. A livestream’s “earliest possible acquisition of signal” refers to when ground controllers might first receive data after separation, not a guarantee of immediate confirmation.

## What BepiColombo Will Study at Mercury

Mercury remains a scientifically unusual world. It is a rocky planet, but it has a disproportionately large iron-rich core and a global magnetic field, features that make it an important test case for models of planetary formation and evolution.

The mission’s two-orbiter approach is intended to provide a more complete picture than a single spacecraft could deliver.

The Mercury Planetary Orbiter will examine topics including the planet’s geology, chemical composition, tenuous exosphere and internal structure. Its observations could improve understanding of how Mercury formed, why its core is so large and how its surface has changed through volcanism, impacts and space weathering.

Mio will focus on Mercury’s magnetosphere: the region dominated by the planet’s magnetic field. Because Mercury is so close to the Sun, the solar wind interacts strongly with this small magnetic bubble. Studying that interaction can reveal how magnetic environments behave under intense solar conditions.

The combined data may also help researchers understand rocky exoplanets that orbit close to their stars. While no exoplanet is a perfect Mercury analogue, the physical processes affecting a sun-baked rocky world can offer valuable clues for interpreting distant planetary systems.

## A European-Japanese Mission With a Long Legacy

BepiColombo follows NASA’s Mariner 10 and MESSENGER missions, both of which transformed knowledge of Mercury. Mariner 10 made the first spacecraft flybys of the planet in the 1970s. MESSENGER later became the first spacecraft to orbit Mercury, operating from 2011 to 2015.

Those missions revealed a world with widespread volcanic plains, water ice in permanently shadowed polar craters and an unexpectedly dynamic magnetic environment.

BepiColombo is designed to build on that foundation with two coordinated spacecraft, modern instruments and prolonged observations from orbit. Its name honours Giuseppe “Bepi” Colombo, an Italian scientist whose work helped explain Mercury’s unusual spin-orbit relationship and contributed to planning the Mariner 10 mission.

The transfer-module separation is not the mission’s scientific finish line. It is the point at which BepiColombo leaves behind a crucial piece of its journey hardware and commits to the final operations required to become a Mercury mission in full.

## What to Watch for Next

The immediate milestone is confirmation that the MTM separated as planned and that the remaining spacecraft are healthy and communicating with Earth.

After that, attention will shift to the final-arrival manoeuvres, Mercury orbit insertion and the eventual deployment of the MPO and Mio orbiters. Once routine science observations begin, BepiColombo should provide years of data on a planet that remains difficult to reach and surprisingly complex to understand.

For now, the key takeaway is measured rather than dramatic: after eight years in flight, BepiColombo is transitioning from an interplanetary voyage to the final phase of becoming Mercury’s next major orbital observatory.

## Authority sources (external links)

– [ESA’s BepiColombo mission overview](https://www.esa.int/Science_Exploration/Space_Science/BepiColombo)
– [ESA’s BepiColombo Mercury arrival replay listing](https://www.esa.int/ESA_Multimedia/Videos/2026/09/BepiColombo_s_Mercury_arrival_begins_-_full_replay)
– [JAXA’s BepiColombo / Mio mission information](https://www.isas.jaxa.jp/en/missions/spacecraft/current/bepi.html)