On September 3, 2026, the European Space Agency (ESA) and Japan Aerospace Exploration Agency (JAXA)–led BepiColombo mission initiated its Mercury Arrival Phase,
marking the start of one of the most complex planetary maneuvers in space history. After eight years of travel, the spacecraft’s Mercury Transfer Module (MTM) separated from its orbiters, setting the stage for Mercury’s orbit insertion in November 2026.
The BepiColombo mission, launched on October 20, 2018, is a joint mission between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) to study Mercury. The spacecraft consists of two orbiters—the European Mercury Planetary Orbiter (MPO) and the Japanese Mercury Magnetospheric Orbiter (MMO or Mio)—stacked atop the MTM, which has powered the journey through interplanetary space. On September 3, 2026, the MTM separated from the orbiters, a critical step in the mission’s arrival sequence, as reported by ESA.
A High-Stakes Arrival Sequence
The separation of the MTM was described as one of the most operationally challenging planetary arrival sequences
ever attempted by ESA. Ignacio Tanco, flight director of ESA’s inner solar system missions, emphasized the difficulty, comparing it to launching a new spacecraft
but around a different planet. The maneuver occurred at 8 am EDT (14:00 CEST), with mission teams monitoring the spacecraft’s status to confirm its health. A signal acquisition was expected by 15:53 CEST, followed by a series of checks to ensure the orbiters were on track for Mercury’s orbit.
Despite meticulous planning, the mission faces significant risks. The extreme temperatures on Mercury, ranging from -180 to 450 degrees Celsius, and solar radiation pose challenges for the spacecraft. ESA acknowledged the challenges of the environment, noting that the area around Mercury is inhospitable to say the least.
Scientific Goals and Technical Challenges
BepiColombo’s primary objective is to study all aspects of the planet, including its mineralogy, elemental composition, magnetosphere, and interaction with the solar wind, as well as its form, interior, structure, geology, and craters. The MPO, equipped with 11 instruments, will map the planet’s mineralogy and elemental composition, while the MMO, carrying five instruments, will investigate Mercury’s magnetosphere. The mission’s unique dual-spacecraft approach allows for simultaneous observations.
Getting to Mercury required a carefully planned trajectory. Unlike direct flights, BepiColombo used repeated gravity assists—a flyby of Earth, two close passes of Venus, and six encounters with Mercury—to slow down, alongside its ion propulsion system.
Next Steps and Timeline
Following the MTM separation, the MPO and MMO will enter orbit around Mercury together in November 2026, with the MMO set to be released by the MPO in December 2026. The MPO will then occupy a 480×1500 km polar orbit, while the MMO will occupy a 590×11640 km polar orbit. Science operations are scheduled to begin in the first week of April 2027, with both orbiters having an operational lifespan of one year with a possible extension of another year.
The ESA has livestreamed the separation process from ESA’s European Space Operations Centre (ESOC) in Darmstadt, Germany. The agency emphasized the mission’s significance, noting that BepiColombo is the world’s first dual-spacecraft mission to Mercury, and only the second mission ever to orbit around the planet.
Why It Matters
BepiColombo’s arrival marks a major step in planetary science, offering insights into Mercury’s environment. For ESA and JAXA, the mission is operated under ESA leadership. As ESA’s Ignacio Tanco noted, the arrival is a significant challenge.
The next major step would be the separation of the orbiters in Mercury’s orbit, which is scheduled for December this year, followed by the start of science operations in April 2027. For now, mission teams are focused on listening for BepiColombo’s post-separation acquisition of signal and carrying out the first checks to confirm the spacecraft is healthy.
