After nearly eight years in flight, BepiColombo has entered the arrival phase at Mercury, a milestone that turns a long cruise through the inner solar system into the mission’s final operational stretch on the event date, September 3, 2026.
The joint European Space Agency and Japan Aerospace Exploration Agency mission released its Mercury Transfer Module to begin the sequence that will eventually place two spacecraft into orbit around the planet. The separation leaves ESA’s Mercury Planetary Orbiter, known as MPO, and JAXA’s Mercury Magnetospheric Orbiter, or Mio, attached together for the last approach.
Mission officials said the next leg will take about six months. Orbital insertion is scheduled for November 21, after which a further sequence of maneuvers will gradually lower and reshape the spacecrafts’ path around Mercury. That schedule matters because arrival at Mercury is unusually complex. Unlike missions that simply fire a major engine burn and settle in, BepiColombo must use a staged process to shed speed and manage the gravitational pull of the innermost planet.
The journey to this point began with launch on October 19, 2018, aboard an Ariane 5 rocket from Europe’s Spaceport in French Guiana. The original plan expected a journey of about seven years, but the mission has spent longer in transit after a solar-panel problem in April 2024 reduced the power available to the transfer module’s electric thrusters. Engineers adjusted the trajectory and preserved the mission, but the fix pushed the arrival date from December 2025 to November 2026.
The cruise phase included flybys of Earth, Venus and Mercury as the spacecraft bled off energy to fall inward toward the Sun. That path is a reminder of how difficult it is to reach Mercury at all. The planet sits deep in the Sun’s gravity well, so getting there is less about speed than about carefully removing it.
The mission’s final architecture is split between its two science spacecraft. Mio is expected to separate from MPO around December 9 and settle into a highly elliptical polar orbit. MPO will then jettison Mio’s sunshield and interface structure on December 16 before continuing toward its own polar orbit on March 10, 2027. Science operations are slated to begin on April 6, 2027.
Those two spacecraft will study Mercury from different perspectives. MPO will focus on the planet’s surface composition, geology and interior, while Mio will examine Mercury’s magnetic field and how it interacts with the solar wind. The combined data set is expected to give scientists a much fuller picture of a world that has remained one of the least studied in the solar system.
For now, the key milestone is simply that the mission has crossed from interplanetary travel to arrival operations. That is not the same as being in orbit, but it is the point at which the long patience of the mission begins to narrow into the final sequence that will determine whether BepiColombo completes one of Europe and Japan’s most technically demanding planetary projects.
