Mercury mission carrying Leicester instrument starts final year of its long journey
The MIXS instrument.
Space scientists at the University of Leicester are marking the final year before the cutting-edge instrument they designed and built will arrive in orbit around the planet Mercury.
The ESA/JAXA BepiColombo mission has been cruising towards Mercury since October 2018. With just one year to go until it arrives at its destination, what has the mission achieved so far? And what can we expect from its two spacecraft after they enter orbit around the Solar System’s smallest and least-explored rocky planet?
During the last seven years, BepiColombo has swung past Earth once, Venus twice and Mercury six times. Aside from investigating the planets, the mission monitored solar activity and studied how the Sun's gravity affects radio signals by bending spacetime itself.
The mission’s main ‘science phase’ will only start after ESA's Mercury Planetary Orbiter (MPO) and JAXA's Mercury Magnetospheric Orbiter (MMO, or Mio) spacecraft enter orbit around Mercury, but scientists and engineers have made the most of the mission’s winding journey to its destination.
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 and Principal Investigator (PI) for the MIXS instrument.
Professor Bunce said: “We have just celebrated 7 years since the launch of ESA/JAXA BepiColombo mission to Mercury, the first two spacecraft mission to another planet. The spacecraft are now just one year away from orbit insertion at Mercury – it’s been a long journey!
“We are looking forward to the ‘first light’ from the Mercury Imaging X-ray Spectrometer (MIXS) in September 2026 when we calibrate the instrument using the Crab Nebula, once we have separated from the Mercury Transfer Module. BepiColombo will then enter into orbit at Mercury on 21st November 2026, and we will commission the Leicester-led MIXS for science operations in Spring 2027. We are now on the countdown to our mission beginning, and the whole team is really excited to see the first MIXS science data from Mercury!”
BepiColombo will be the first mission to study Mercury with two spacecraft at the same time. MPO will orbit close to the planet’s surface, and Mio in a larger elliptical orbit.
So far, MPO and Mio – the latter nestled inside a protective sunshield – have been stacked on top of their ‘trusty engine’ MTM. Several of the mission’s scientific instruments can’t yet be used, or are partially hindered, until the stacked spacecraft separate after arriving at Mercury in November 2026.
Once ‘unstacked’, MPO and Mio can separate and will then be captured into their respective orbits, only then can they finally use all their instruments to their full scientific potential.
For example, instead of the modest black-and-white images taken by MTM’s monitoring cameras, MPO will scan Mercury’s surface in high resolution in X-rays (with imaging spectrometer MIXS), visible and near-infrared light (with stereo camera and spectrometer SIMBIO-SYS) and infrared light (with imaging spectrometer MERTIS). To ensure that we accurately capture Mercury’s topography, MPO’s BELA laser altimeter instrument will measure the precise height and shape of Mercury’s surface.
Put together, this data will give us a precise map of Mercury’s surface, and tell us what it’s made of, how it formed, how it changes over time, and what temperature it is. Flying over Mercury’s poles, MPO will also be able to peer into craters in permanent shadow – if there is water ice on Mercury, this is where it would be!
While we wait for the spacecraft to reach Mercury, an animated video has been produced to explain more about the mission.