Scientists hail final flyby for Mercury mission with Leicester technology

A spacecraft carrying an instrument designed and built by University of Leicester scientists has completed its final flyby of Mercury, in preparation for entering orbit ready for the start of its start of the science mission in 2026/7.

On 8 January 2025, the ESA/JAXA BepiColombo mission flew past Mercury for the sixth time, successfully completing the final ‘gravity assist manoeuvre’ needed to steer it into orbit around the planet in late 2026. The spacecraft flew just a few hundred kilometres above the planet's north pole. Close-up images expose possibly icy craters whose floors are in permanent shadow, and the vast sunlit northern plains.

At 06:59 CET, BepiColombo flew just 295 km above Mercury's surface on the planet's cold, dark night side. Around seven minutes later, it passed directly over the Mercury's north pole before getting clear views of the planet's sunlit north.

BepiColombo carries the Mercury Imaging X-ray Spectrometer (MIXS), developed by a Europe-wide consortium led by the University of Leicester, including institutes and companies in the UK, Finland, Spain, Germany and France. Professor Emma Bunce is Director of the University of Leicester’s Institute for Space Leicester and Principal Investigator (PI) for the MIXS instrument.

Professor Bunce said: “It is hard to believe that six years have passed since the incredible launch of BepiColombo and the University of Leicester-led Mercury Imaging X-ray Spectrometer (MIXS). During those six years the spacecraft has been journeying inward in the solar system towards Mercury, and all the while we have been slowing the spacecraft down using thrusters and multiple planetary flybys. This Mercury flyby is the sixth and final flyby manoeuvre and from now on we are in cruise, using the thrusters to make the final adjustments before the spacecraft is captured into orbit at Mercury in 2026. 

“Each successful flyby is a major milestone for ESA and for the whole science team, and we are excited to be getting closer to the main science mission where our MIXS instrument will make ground-breaking X-ray observations of the planetary surface and space environment from a close orbit around Mercury.”

Dr Simon Lindsay, MIXS Instrument Operations Scientist at the University of Leicester said: “MIXS is an X-ray spectrometer that will measure and map the composition of Mercury’s surface once the mission starts in 2026-7. We and our colleagues across the world are very excited for the data we will get back from Mercury, which will allow us to investigate Mercury’s surface, environment, formation and history. 

“During the Mercury flybys in our cruise configuration BepiColombo travels as a stack of three spacecraft and our instrument is unable to see out of this stack. Despite that, we operated MIXS throughout the flyby - both as a health check and to observe cosmic rays, particles from outside the solar system which have such enormous energy that they are able to pass through the spacecraft itself and reach our detectors. The science we’ve seen from MIXS and the other BepiColombo instruments during the Mercury flybys so far has already led to some exciting results, and we are very aware that this is only a tiny preview of what to expect from Mercury orbit!”

Dr Adrian Martindale, Head of Space Projects and Instrumentation at the University’s £100 million science and innovation park Space Park Leicester, said: “Missions like BepiColombo are career defining projects. Our team, from the School of Physics and Astronomy have been involved in BepiColombo since the turn of the century, growing MIXS from an idea into a real, working instrument that we are now operating in space. Our next interaction with Mercury will be when we finally get captured into orbit and our team will be ready to capitalise on the decades of work that our fantastic team of scientists, engineers, technicians and administrators have invested to provide this opportunity for us. I am excited to start operating MIXS from our new facilities at Space Park Leicester - delivering new results to the scientific community.”

European Space Agency (ESA) Director General Josef Aschbacher revealed the first image from this flyby during his Annual Press Briefing on 9 January. As during BepiColombo's previous flybys, the spacecraft's monitoring cameras (M-CAMs) did not disappoint.

This flyby also marks the last time that the mission's M-CAMs get up-close views of Mercury, as the spacecraft module they are attached to will separate from the mission's two orbiters – ESA’s Mercury Planetary Orbiter and JAXA’s Mercury Magnetospheric Orbiter – before they enter orbit around Mercury in late 2026.

Throughout its mission, several BepiColombo instruments will measure the composition of both old and new parts of the planet's surface. This will teach us about what Mercury is made of, and how the planet formed.

"This is the first time that we performed two flyby campaigns back-to-back. This flyby happens a bit more than a month after the previous one," says Frank Budnik, BepiColombo Flight Dynamics Manager. “Based on our preliminary assessment, everything proceeded smoothly and flawlessly.”

“BepiColombo's main mission phase may only start two years from now, but all six of its flybys of Mercury have given us invaluable new information about the little-explored planet. In the next few weeks, the BepiColombo team will work hard to unravel as many of Mercury's mysteries with the data from this flyby as we can,” concludes Geraint Jones, BepiColombo's Project Scientist at ESA.