BepiColombo begins arrival at Mercury after nearly eight years of flight

Nearly eight years after its launch, the joint European Space Agency (ESA) and Japan Aerospace Exploration Agency (JAXA) mission BepiColombo has entered the arrival phase at Mercury. On 3 September 2026, the Mercury Transfer Module released its payload—two scientific spacecraft that will enter orbit around the Sun's closest planet in the coming months.

A Long Journey to the Innermost Planet

BepiColombo launched on 19 October 2018 from the Guiana Space Centre on an Ariane 5 rocket. The flight was originally expected to take about seven years, but the trajectory proved to be one of the most complex in the history of interplanetary missions. To shed excess speed and approach Mercury, the spacecraft performed one Earth flyby, two Venus flybys, and six Mercury flybys.

The situation grew more complicated in April 2024, when a solar panel issue reduced the power available to the electric thrusters. Engineers developed a new trajectory with lower thrust. This saved the mission but delayed arrival from December 2025 to November 2026.

What Happened on 3 September

On the day of separation, the transfer module released the pair of spacecraft: the European Mercury Planetary Orbiter (MPO) and the Japanese Mercury Magnetospheric Orbiter, known as Mio. The two probes themselves remain together for now. According to Bruno Sousa of ESA, this moment effectively marks the beginning of a "new mission."

Entering orbit around Mercury does not involve a single large manoeuvre. Ahead lie about six months of continuous operations. A sequence of 16 manoeuvres will begin on 21 November 2026. Around 9 December, Mio will separate from MPO and enter a highly elliptical polar orbit. On 16 December, MPO will jettison the MOSIF protective shield, which had been covering the Japanese spacecraft, and continue lowering its orbit. The European probe is scheduled to reach its working polar orbit on 10 March 2027.

The science programme is set to begin on 6 April 2027. Both spacecraft will operate simultaneously from complementary orbits: MPO will focus on surface composition, geology, and the planet's internal structure, while Mio will study Mercury's magnetic field and its interaction with the solar wind.

Successful Confirmation

The separation occurred at 12:00 GMT. Signal confirmation came more than an hour later, and telemetry showed that the spacecraft's configuration matched the expected parameters. Mission operations manager Elsa Montagnon noted that everything had gone according to the best-case scenario: the signal appeared exactly at the expected time, and the station's status was nominal.

In Brief

After nearly eight years of flight, the BepiColombo mission began its arrival phase at Mercury on 3 September 2026, with the transfer module releasing its two scientific probes. Six months of manoeuvres lie ahead. Entry into working orbits is scheduled for late 2026 to early 2027, with full scientific observations starting in April 2027. The European spacecraft will study the planet's surface and interior, while the Japanese spacecraft will investigate its magnetic field and interaction with the solar wind.

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