BepiColombo

• 1. The Man Behind The Name

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  Giuseppe Bepi Colombo lived from 1920 to 1984. He worked as a scientist, mathematician and engineer at the University of Padua in Italy. His name now adorns a joint mission between the European Space Agency and the Japan Aerospace Exploration Agency. This spacecraft travels toward Mercury with the goal of studying its magnetic field and surface structure. Colombo first proposed the interplanetary gravity assist maneuver used by the 1974 Mariner 10 mission. That technique is now frequently used by planetary probes across the solar system. The public named the second orbiter Mio after thousands of suggestions were submitted. In Japanese, Mio means a waterway. JAXA stated that it symbolizes research milestones reached thus far. They also wished for safe travel ahead. The spacecraft will travel through the solar wind just like a ship traveling through the ocean. Chinese and Japanese cultures refer to Mercury as the water star.

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• 2. Instruments And Scientific Goals

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  Scientists aim to study the origin and evolution of a planet close to its parent star. They want to investigate Mercury's form, interior, structure, geology, composition and craters. The mission will explore the exosphere, including generation and escape mechanisms. Researchers plan to study Mercury's magnetised envelope or magnetosphere. A key objective involves verifying Einstein's theory of general relativity. Scientists measure parameters gamma and beta of the parameterized post-Newtonian formalism with high accuracy. Mercury has a tenuous surface-bounded exosphere containing hydrogen, helium, oxygen, sodium, calcium, potassium and other trace elements. Atoms are continuously lost and replenished from various sources. Russia provided gamma ray and neutron spectrometers to verify water ice in polar craters. These craters remain permanently shadowed from the Sun's rays. The orbiters carry instruments provided by European countries and Japan. The mission characterizes the solid and liquid iron core of the planet's radius. It determines the size of each component within the core. Gravitational and magnetic field mappings complete the scientific payload.

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• 3. Launch And Gravity Assist Path

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  The two orbiters launched together on the 20th of October 2018. An Ariane flight VA245 carried them from Europe's Spaceport in Kourou, French Guiana. The stacked spacecraft took eight years to position itself for Mercury orbit entry. During this time it used solar-electric propulsion and nine gravity assists. The craft flew past Earth and the Moon in April 2020. It performed two flybys of Venus in 2020 and 2021. Six Mercury flybys occurred between 2021 and 2025. Initially the craft was placed in a heliocentric orbit similar to that of Earth. After both the spacecraft and Earth completed one and a half orbits, it returned to Earth. A gravity-assist maneuver deflected it towards Venus. Two consecutive Venus flybys reduced the perihelion near to the Sun-Mercury distance. This required almost no thrust. A sequence of six Mercury flybys lowered the relative velocity to zero. After the fourth Mercury flyby in 2024, the spacecraft entered an orbit similar to that of Mercury. It remained in the general vicinity of the planet.

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• 4. Venus Observations And Data

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  ESA scientists suggested BepiColombo might detect phosphine during its two Venus flybys. Phosphine had been tentatively discovered in the Venusian atmosphere in September 2020. No announcement confirmed such detection since then. During the first Venus flyby in October 2020, seven science instruments gathered data. Three instruments onboard Mio also collected information. Observations coordinated with JAXA's Akatsuki spacecraft. Earth-based observatories joined the effort. The second Venus flyby happened in August 2021. It occurred only 33 hours after Solar Orbiter completed its gravity assist at the same planet. Both spacecraft used their science instruments to study the magnetic environment around Venus. They studied plasma and particle environments offering unique multipoint datasets. The MPO's MERTIS instrument captured high resolution spectra of the Venus atmosphere. The Mercury Transfer Module's three monitoring cameras documented various phases of the flyby. Black-and-white images showed the planet from multiple angles.

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• 5. Mercury Flyby Discoveries

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  The first Mercury flyby took place in October 2021. The spacecraft captured its first images using M-CAM monitoring cameras on the Mercury Transfer Module. Scientific instruments explored the magnetic and particle environment around Mercury. They measured the planet's gravity during this pass. The second flyby occurred in June 2022. M-CAM cameras imaged the crater Heaney with a candidate volcano. This crater has been named after Seamus Heaney following a request from the team. Instruments measured the magnetic, plasma, and particle environment again. During the third flyby in June 2023, MPPE mapped the magnetosphere of Mercury. Scientists described expected features but made new discoveries. A low latitude layer contained particles with much broader energy range than ever observed. Energetic hydrogen ions trapped at low latitude near the equator appeared. Cold plasma ions of oxygen and sodium were detected. Signatures of potassium were found, probably ejected by micrometeorites or solar wind. Mio identified chirping-like discrete whistler-mode emission waves previously unknown from Mercury. The fourth flyby in September 2024 provided a clear view of Mercury's south pole. Images showed Vivaldi crater and Stoddart crater. The fifth flyby in December 2024 used MERTIS to observe Mercury in mid-infrared light. The sixth final flyby happened in January 2025. It imaged permanently shadowed craters Prokofiev, Kandinsky, Tolkien, and Gordimer.

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• 6. Thruster Malfunction And Delay

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  ESA reported an issue on the 15th of May 2024 preventing thrusters from operating at full power. This occurred during a scheduled maneuver on the 26th of April 2024. On the 2nd of September 2024, ESA announced a revised trajectory would add eleven months to the cruise. The delay pushed arrival from the 5th of December 2025 to November 2026. Four final thrust arcs will reduce relative velocity for weak capture into polar orbit. A small maneuver brings the craft into an orbit with apocentre of 590 kilometers. Orbiters separate and adjust orbits using chemical thrusters. Computers on BepiColombo reported sharp increases in memory errors in May 2024. This coincided with a massive solar flare from active region AR3664. The event was observed by Solar Orbiter. The mission timeline now extends through early 2027. Nominal operations end in April 2028. Planned extended mission runs until April 2029.

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