BepiColombo, the joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) dedicated to studying Mercury, has reached a major milestone. On 15 September, SIMBIO-SYS (Spectrometers and Imagers for MPO BepiColombo Integrated Observatory System) activated its three optical channels for the first time in their final configuration, demonstrating the system’s proper operation and capturing its first image. SIMBIO-SYS is one of the mission’s flagship scientific instruments and represents an important achievement in international collaboration, with Italy playing a leading role through strong support from the Italian Space Agency (ASI), the scientific leadership of the National Institute for Astrophysics (INAF), and the contribution of Italian industry.
The first light came after almost eight years of interplanetary cruise and following the separation, on 3 September, of the module that accompanied BepiColombo during its long journey to Mercury. The tests carried out on 15 September were successful, and the first telemetry data confirm that the instrument is operating correctly. Over the coming weeks, the team will also fine-tune some operational conditions to prepare SIMBIO-SYS for the mission’s scientific observations.
SIMBIO-SYS was designed to observe Mercury from different and complementary perspectives. Its three channels will work in cooperation to build a comprehensive portrait of the planet, combining stereoscopic and high-resolution images with information on the composition of its surface.
The first is the Stereo Imaging Channel (STC), dedicated to stereoscopic imaging. It will acquire images from two different viewing angles while the spacecraft orbits Mercury. This will make it possible, for the first time, to create a global three-dimensional map of the planet. The images will have a resolution of up to approximately 60 metres per pixel, allowing scientists to identify craters, tectonic structures, volcanic landforms and other surface features.
The second is the High Resolution Imaging Channel (HRIC), dedicated to high-resolution imaging, with a resolution of approximately 6 metres per pixel. It will allow scientists to observe much smaller surface details than those visible in global mapping images. It will be particularly useful for studying impact craters, geological structures, volcanic features and other processes that have shaped the planet’s surface.
The third is the Visible and Near-Infrared Hyperspectral Imager (VIHI), dedicated to hyperspectral analysis. It will analyse light reflected from the surface in the visible and near-infrared wavelengths. It will therefore not simply show what the terrain looks like, but will also help determine which materials and minerals it is made of. Researchers can then correlate composition with the shape of the surface and its geological history.
The combination of the three channels is one of SIMBIO-SYS’s most innovative features: images, topographic information and compositional data will be collected and interpreted together, providing a comprehensive view of Mercury’s surface.
“SIMBIO-SYS’s first light is a particularly significant moment for the entire instrument team: after almost eight years of interplanetary cruise, the instrument has acquired its first images,” says Raffaele Pepe, ASI Head of Scientific and Industrial Activities for the SIMBIO-SYS instrument. “These images first and foremost confirm the instrument’s health and have allowed us to verify the correct operation of the acquisition systems after such a long and complex journey. This is therefore a fundamental step ahead of the mission’s upcoming scientific activities. It is an important achievement for the Italian scientific and industrial community, which has made a significant contribution to the development of SIMBIO-SYS and to its preparation for this complex mission to Mercury.”
“Although this is SIMBIO-SYS’s first attempt to observe the sky, we were able to capture several stars as bright points with STC,” comments Gabriele Cremonese, INAF researcher and SIMBIO-SYS Principal Investigator. “We are extremely pleased with this result, as it confirms the instrument’s potential to deliver excellent performance once we begin observing Mercury. We are excited that scientific observations of the planet can begin with the nominal mission in April 2027. This first light confirms the excellence of the Italian scientific and industrial community, together with the Italian Space Agency, in the development of space instruments.”
Behind SIMBIO-SYS is a major international collaboration built over many years, bringing together scientific, technological and industrial expertise. At the core of the team are 118 scientists and engineers from twelve countries, supported by numerous researchers and early-career scientists who prepare observations, operate the instrument and analyse the data.
Italy plays a leading role in this team: ASI has supported the instrument’s development with the support of the French Space Agency (CNES), while INAF leads its scientific component. Italian industry complements this effort, with Leonardo serving as the industrial partner for the integrated SIMBIO-SYS experiment. This collaboration between research institutions, space agencies and industry has made it possible to bring an instrument aboard BepiColombo designed to address fundamental questions about the history of Mercury.
Mercury is the smallest of the Solar System’s rocky planets and the closest to the Sun. It is also, apart from Earth, the only planet to possess a global magnetic field. Despite its proximity, it remains largely unexplored. SIMBIO-SYS observations will help reconstruct the planet’s history: from its volcanic and tectonic activity to the major impacts that have shaped its surface, and from the nature of the materials on the ground to the interactions between the surface and the surrounding environment.
Launched in October 2018, BepiColombo is now approaching the final phase of its journey. Mercury orbit insertion will begin on 21 November 2026. SIMBIO-SYS’s first light marks a major step toward the mission’s scientific phase, when the images and data collected will help reveal Mercury’s history in unprecedented detail. Another key milestone will be the separation of MPO (Mercury Planetary Orbiter), ESA’s spacecraft, and Mio (Mercury Magnetospheric Orbiter), JAXA’s spacecraft, scheduled for 9–10 December 2026. From this separation onwards, BepiColombo will be the first mission to operate two spacecraft in orbit around Mercury.
