BepiColombo begins Mercury arrival with MTM separation success

Over the last eight years, BepiColombo has travelled 9.9 billion kilometres through the inner Solar System and completed nine planetary flybys to reach this historic milestone. Despite parting with the module, BepiColombo would not have made it this far without MTM. It carried BepiColombo from Earth to Mercury, providing power and the highly advanced solar electric propulsion (SEP) needed to navigate its complex space journey. Now, MTM’s job is complete.

This separation is the first in a sequence of key manoeuvres that will ultimately see BepiColombo become the first mission to place two spacecraft in orbit around Mercury, in December 2026. The mission's Mercury arrival phase is one of the most complex planetary arrival sequences ever attempted by ESA.

After an intense day of operations at ESA's mission control centre in Darmstadt, Germany, ESA, industry partners and the mission's scientific community celebrated the acquisition of signal confirming MTM's successful separation. Thousands also followed the milestone live on ESA's YouTube channel.

Letting go

In the months leading up to MTM separation, rigorous simulations challenged the Mission Control Team (MCT) with a wide range of operational scenarios. 

On 3 September 2026 came the real deal. At 12:00 CEST, the team gave the official "GO" for separation. For those in the Main Control Room, it marked the culmination of months of preparation.

As the expected separation time arrived at 14:00 CEST, silence fell over mission control. The team would have to wait nearly two hours for confirmation to arrive from 200 million kilometres away.

Following separation, the remaining spacecraft stack entered safe mode, readjusted its attitude and reconfigured itself before transmitting its status back to Earth. 

At 14:20 CEST, a preliminary Doppler signal provided the first indication that separation had taken place. 

"We heard it loud and clear in the voice loop from Flight Dynamics Manager, Frank Budnik, that they could clearly see from the Doppler data that MTM had separated. After all this waiting and preparation, we all looked at each other and hugged. It was a very powerful moment," says Emmanuela Bordoni, ESA BepiColombo B-shift Spacecraft Operations Manager.

With ESA's Estrack Cebreros and Malargüe deep-space antennas locked on target, all eyes turned to the incoming telemetry. 

At 15:49 CEST, mission control received the long-awaited acquisition of signal, prompting cheers and applause. 

"We are thrilled, but also relieved. Separating two spacecraft from 200 million kilometres away is not something we do every day. We have prepared intensively for this moment, so we are really pleased to have had a perfect separation," says a beaming Ignacio "Nacho" Clerigo, ESA BepiColombo Spacecraft Operations Manager. 

Farewell MTM

Every great collaboration deserves a proper goodbye. 

On its final day as part of BepiColombo, MTM captured its last images, continuing a role it had fulfilled throughout the mission's journey to Mercury. 

Alongside its solar arrays and ion thrusters, MTM carried three monitoring cameras that documented the voyage. During the cruise phase, they captured daily snapshots of the spacecraft's journey through the inner Solar System. 

The final images marked the closing entry in an eight-year photo diary and the end of a remarkable collaboration that carried the mission to Mercury's doorstep. 

A full collection of these images is available in the ESA Planetary Science Archive. 

As for MTM, with no antenna or onboard computer of its own, the now inoperable module will remain in a stable orbit around the Sun. 

"We feel a bit sad to see our old friend MTM going away. It did an astonishing job bringing MPO and Mio here, but as Freddie Mercury once sang, the show must go on!" says Nacho. 

To mark the achievement, the MCT took part in one of ESOC's most enduring traditions: the sticker ceremony. On the day after separation, the team gathered to add the MTM sticker on the Briefing Room glass door, securing its place among the missions that have shaped ESOC's history.  

"I feel so proud of this team. This is the perfect start to arrival phase," says a smiling Santa Martínez Sanmartín, ESA BepiColombo Mission Manager. 

Carrying the mission

Roughly the size of a small car, the Mercury Transfer Module carried two 15-metre-long solar wings that powered the entire spacecraft stack and propelled it using its highly advanced solar electric propulsion (SEP) system. 

This technology uses solar energy to turn xenon gas into plasma that is expelled through four ion thrusters. Unlike chemical propulsion, which provides short, powerful bursts of acceleration, SEP delivers gentle but continuous thrust for days, weeks or even months while using far less propellant. 

This efficiency is what made BepiColombo's complex journey to Mercury possible. Along the way, the mission overcame significant challenges. BepiColombo's route to Mercury needed a mid-course rethink after an issue reduced the power available from MTM's solar arrays. Mission teams adapted the trajectory, allowing the spacecraft to remain on track for arrival. 

On 15 June 2026, SEP was switched off, bringing MTM's primary mission to an end and setting up the next major milestone which we saw on 3 September – MTM separation. 

What is next for BepiColombo?

Following MTM separation, BepiColombo is still more than three million kilometres from Mercury. 

Unlike most interplanetary missions, arrival is not a single event but a six-month sequence of carefully choreographed manoeuvres.

“The next separation will be Mio. After seeing the successful separation of MTM I feel confident about what lies ahead”, says JAXA's BepiColombo Project Scientist, Go Murakami. 

With MTM's job complete, the remaining spacecraft stack now enters a new phase of the journey. Using MPO's chemical propulsion system, the MCT will fine-tune the trajectory ahead of Mercury orbit insertion on 21 November. Mio will then be deployed in early December, before MPO is guided into its final science orbit in March 2027. 

"Although we already have great science from the cruise phase and nine planet flybys, it's fantastic that we've taken this first important step towards finally being able to use all the powerful instruments on both MPO and Mio to study Mercury," says ESA BepiColombo Lead Project Scientist, Geraint Jones. 

By April 2027, the two spacecraft will begin their scientific investigations, offering unprecedented insights into Mercury's surface, interior, magnetic field and surrounding environment. 

 

Stay tuned for more BepiColombo updates as we get closer to Mercury!