# BepiColombo Launch Opens New Chapter in Mercury Exploration Canonical URL: https://www.teknalyze.com/on-this-day/bepicolombo-launch-2018/ Published: 2026-10-20 Updated: 2026-10-20 Author: Teknalyze Desk Section: On This Day Categories: On This Day, Technology Primary topic: BepiColombo, Mercury Exploration, JAXA, ESA, Ariane 5 rocket Historical event date: 2018-10-20 ## Event summary On October 20, 2018, the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) launched BepiColombo aboard an Ariane 5 rocket, beginning one of the most technically demanding journeys in planetary exploration. ## Fact box Event: BepiColombo Launch Opens New Chapter in Mercury Exploration Date: October 20, 2018 People or organization: Not stated in the article Why it matters: These encounters helped reduce the amount of propellant required to reach the planet, while the spacecraft’s electric propulsion system provided additional trajectory adjustments during its long cruise. ## Key points - BepiColombo was designed to build on those discoveries with a more comprehensive investigation. - The next major milestone is scheduled for November 21, 2026, when BepiColombo is expected to enter orbit around Mercury. - Further commissioning activities are planned for early 2027, with routine scientific operations expected to begin in April 2027. ## Historical context Before BepiColombo, only two spacecraft missions had visited Mercury: NASA’s Mariner 10, which conducted flybys during the 1970s, and MESSENGER, which orbited the planet from 2011 to 2015. Those missions revealed a heavily cratered surface, evidence of extensive volcanic activity, and a surprisingly complex magnetic environment. ## Article On October 20, 2018, the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) launched BepiColombo aboard an Ariane 5 rocket, beginning one of the most technically demanding journeys in planetary exploration. Its destination was Mercury, the smallest planet in our solar system and one of the most challenging to reach because of its proximity to the Sun. Eight years later, in October 2026, the mission is approaching a defining milestone. After traveling billions of kilometers through the inner solar system, BepiColombo is preparing to enter orbit around Mercury in November 2026, bringing its two scientific spacecraft closer to beginning their long-awaited investigations. The mission aims to reveal how Mercury formed, why it possesses a global magnetic field, and what its surface and interior can tell scientists about the evolution of rocky planets. More than a journey to another world, BepiColombo represents an ambitious effort to understand a planet whose unusual characteristics continue to challenge scientific explanations of how the solar system developed. ### Why Mercury Is So Difficult to Explore Despite being relatively close to Earth compared with the outer planets, Mercury presents extraordinary engineering challenges. A spacecraft traveling toward the Sun gains speed as it descends deeper into the Sun’s gravitational field, making it difficult to slow down enough to enter Mercury’s orbit. Reaching the planet therefore requires more than pointing a rocket in the right direction. Engineers must carefully manage the spacecraft’s trajectory and orbital energy while minimizing fuel consumption. Mercury’s environment adds another layer of complexity, with intense solar radiation and extreme surface temperature variations requiring specialized thermal protection for instruments and spacecraft systems. Before BepiColombo, only two spacecraft missions had visited Mercury: NASA’s Mariner 10, which conducted flybys during the 1970s, and MESSENGER, which orbited the planet from 2011 to 2015. Those missions revealed a heavily cratered surface, evidence of extensive volcanic activity, and a surprisingly complex magnetic environment. However, significant questions remained about Mercury’s unusually large metallic core, its geological evolution, and the interaction between its magnetic field and the solar wind. BepiColombo was designed to build on those discoveries with a more comprehensive investigation. ### Two Orbiters Designed to Unlock Mercury’s Secrets BepiColombo is a joint European-Japanese mission built around two complementary scientific spacecraft. ESA’s **Mercury Planetary Orbiter (MPO)** will study the planet’s surface, internal structure, geological history, and composition, using specialized instruments to investigate how Mercury formed and evolved. JAXA’s **Mercury Magnetospheric Orbiter, named Mio**, will examine the planet’s magnetic field, surrounding plasma environment, and interactions with charged particles from the Sun. Together, the orbiters will provide different perspectives on Mercury, allowing scientists to investigate connections between its interior, surface, and surrounding space environment. The mission also included the **Mercury Transfer Module (MTM)**, which used solar-electric propulsion to carry the two orbiters across the inner solar system. This configuration allowed BepiColombo to combine an efficient interplanetary transport system with spacecraft specifically engineered for scientific operations near Mercury. The dual-orbiter approach is particularly valuable because simultaneous measurements from different locations can help distinguish changes caused by the solar wind from processes occurring within Mercury’s own magnetic environment. ### An Eight-Year Journey Through the Inner Solar System BepiColombo’s journey was far more complicated than a direct flight. To reach Mercury efficiently, the spacecraft combined solar-electric propulsion with a carefully planned sequence of gravitational assists, using planetary encounters to progressively adjust its trajectory and orbital energy. Over nearly eight years, it completed nine planetary flybys: one of Earth, two of Venus, and six of Mercury. These encounters helped reduce the amount of propellant required to reach the planet, while the spacecraft’s electric propulsion system provided additional trajectory adjustments during its long cruise. The final Mercury flyby took place in January 2025, completing the gravity-assist sequence that had guided the mission toward its destination. The journey also provided opportunities for early scientific observations. During its Mercury flybys, BepiColombo collected images and measurements that offered additional perspectives on the planet’s surface and surrounding environment. Although the spacecraft’s cruise configuration limited some scientific instruments, these encounters allowed mission teams to test equipment, refine operational procedures, and gather useful data before orbital arrival. The mission demonstrated how modern planetary exploration increasingly depends on a combination of precision navigation, efficient propulsion, international coordination, and long-term spacecraft reliability. ### October 2026: BepiColombo Prepares to Enter Mercury’s Orbit As BepiColombo approaches its eighth launch anniversary, the mission is entering its final arrival phase. In June 2026, engineers permanently switched off the Mercury Transfer Module’s solar-electric propulsion system after completing the final planned thrust arc. On September 3, 2026, the transfer module separated from the remaining spacecraft assembly, completing its role in transporting BepiColombo across the inner solar system. By that point, the mission had traveled approximately **9.9 billion kilometers** along the looping trajectory required to reach Mercury. The two scientific orbiters remain connected during the final approach, with ESA’s Mercury Planetary Orbiter responsible for the propulsion maneuvers needed to enter orbit. September also brought important technical milestones as engineers activated scientific instruments that had been constrained during the cruise. ESA’s BELA laser altimeter successfully fired more than 700,000 laser pulses during a 21.5-hour test, while the MERTIS thermal imaging spectrometer completed a performance check that collected approximately one gigabit of data. These tests provided encouraging evidence that the instruments were functioning after years in space. The next major milestone is scheduled for **November 21, 2026**, when BepiColombo is expected to enter orbit around Mercury. JAXA’s Mio spacecraft is subsequently scheduled to separate from MPO in December, allowing the two orbiters to establish their respective orbital configurations. Further commissioning activities are planned for early 2027, with routine scientific operations expected to begin in April 2027. ### Why BepiColombo Matters for Planetary Science Mercury occupies a particularly interesting position in planetary science because its physical characteristics differ significantly from those of other rocky planets. Despite its small size, Mercury possesses an unusually large iron-rich core and a global magnetic field, raising important questions about its formation and internal evolution. BepiColombo will investigate these mysteries through measurements of the planet’s gravity, magnetic environment, surface composition, and geological features. Its instruments will also study Mercury’s extremely thin exosphere and the ways in which solar radiation and charged particles interact with the planet. The mission’s findings could extend beyond Mercury itself. Understanding how a relatively small planet maintains a magnetic field may help scientists refine models of planetary interiors and magnetic dynamos, while detailed surface observations could provide new evidence about volcanic activity, crustal formation, and tectonic processes. Mercury’s proximity to the Sun also makes it a valuable natural laboratory for studying the interaction between planetary magnetic fields and the solar wind, with implications for understanding similar processes elsewhere in the solar system, including around Earth. ### A Mission Nearing Its Most Important Chapter Looking back at October 20, 2018, the launch of BepiColombo represented an ambitious commitment to studying one of the solar system’s most difficult planetary destinations. Its success so far has depended on advanced electric propulsion, specialized thermal engineering, precise gravitational navigation, and sustained cooperation between European and Japanese space agencies. By October 2026, the spacecraft has completed its nine planetary flybys, finished its solar-electric propulsion phase, separated from its transfer module, and begun preparing its scientific instruments for orbital operations. These achievements have brought the mission to the threshold of the investigations for which it was designed. With Mercury orbit insertion scheduled for November 2026 and scientific operations expected to begin in April 2027, BepiColombo is transitioning from a remarkable engineering journey toward a new phase of planetary discovery. The observations collected by its two orbiters could help answer longstanding questions about Mercury’s unusual interior, magnetic field, and geological history, while improving scientific understanding of how rocky planets evolve under extreme conditions. **Eight years after launch, BepiColombo is approaching the moment it was built for: studying Mercury from orbit and revealing new details about the solar system’s innermost planet.** ## Sources No external source is cited in this article. ## Sources No external source is cited in this article.