Following an eight-year journey through the inner Solar System, the joint European Space Agency and Japan Aerospace Exploration Agency mission has begun its arrival phase at Mercury, setting up an orbit insertion on November 21, 2026.
Separation of the Mercury Transfer Module on September 3, 2026
The arrival sequence kicked off on September 3, 2026, when the Mercury Transfer Module separated from the spacecraft stack. Acquisition of signal via Estrack deep space antennas in Cebreros, Spain, and Malargüe, Argentina, confirmed the milestone at 14:52 BST. Mission control teams at the European Space Operations Centre confirmed all telemetry was nominal, leaving ESA’s Mercury Planetary Orbiter to power the combined stack.
Executing a critical separation more than 200 million kilometres from Earth demanded precise planning and commanding with no window for real-time intervention. Following the maneuver, the spacecraft is on its way towards orbit insertion around Mercury.
Instrument Checkouts and First Light Tests in Space
With the transfer module out of the way, engineers powered on all instruments aboard ESA’s Mercury Planetary Orbiter simultaneously on September 15 for the first time. Preliminary analyses showed the suite operating in good health. The BELA laser altimeter emitted over 700 thousand pulses into open space across a 21.5-hour test, demonstrating excellent health since its last full ground check in 2016.
Next stop, Mercury.After an eight-year journey, ESA/JAXA's BepiColombo is nearing arrival at its destination. Explore the key milestones, timeline and science behind the mission in our new media kit: https://t.co/8U13FgTu5X pic.twitter.com/ZRQ4SkraG4
At the same time, the Mercury Radiometer and Thermal Imaging Spectrometer observed deep space through its calibration and planet viewing ports, which were previously blocked by the transfer module during earlier flight fly-bys. The test returned roughly 1 gigabit of data and revealed little to no loss in spectrometer sensitivity since its low-temperature ground calibration in 2013. Meanwhile, the SIMBIO-SYS science camera activated its three optical channels to capture its first space image successfully.
Orbits and Separation Milestones Leading to April 2027 Science Phase
The composite spacecraft is scheduled to enter orbit around Mercury on November 21, 2026. Following orbital insertion, the European orbiter and Japan’s Mercury Magnetospheric Orbiter will separate from each other on December 9 to 10, 2026, allowing each craft to take up its respective path. The mission’s dedicated science phase is set to officially begin in April 2027.
Despite these advances, planetary scientists emphasize that major questions regarding the innermost planet will persist. Mercury features a disproportionately large iron-rich core that is thought to make up some 85 percent of the planet’s radius.
Challenges of Future Surface Exploration Without a Lander
Beyond its core, Mercury features unusual surface material that may contain endogenic carbon such as graphite, hinting at an ancient graphite-rich flotation crust.
Yet researchers note that solving these fundamental puzzles permanently will likely require a dedicated lander mission. For now, however, no lander is on the drawing board, leaving the upcoming orbital arrivals as our primary window into the solar system’s most elusive rocky planet.