After nearly eight years of navigating the inner solar system, the BepiColombo spacecraft has officially entered its arrival phase at Mercury, according to the European Space Agency and the Japan Aerospace Exploration Agency. The joint mission reached this milestone when its Mercury Transfer Module separated from its payload of planetary probes, initiating a complex six-month sequence that will place the spacecraft into orbit around the solar system’s least-studied rocky planet.
Spacecraft Separation Triggers Final Approach
The separation occurred at 8:00 a.m. EDT, with acquisition of signal confirmed by mission controllers just before 10 a.m. EDT, according to operations manager Elsa Montagnon. The action released the Mercury Transfer Module, leaving the ESA Mercury Planetary Orbiter and JAXA Mercury Magnetospheric Orbiter, known as Mio, coupled together for their final approach. Bruno Sousa, ESA’s head of operations definition and engineering, described the event during a mission livestream by stating that it will basically be a new mission starting today.
Launched on Oct. 19, 2018, aboard an Ariane 5 rocket from the Guiana Space Center in Kourou, French Guiana, the spacecraft utilized a trajectory involving one Earth flyby, two Venus flybys, and six Mercury flybys to shed gravitational energy. Sousa characterized it as one of the most complicated missions ever flown. That complexity increased in April 2024 when a solar panel issue reduced power to the transfer module’s electric thrusters, prompting engineers to devise a lower-thrust trajectory that delayed arrival from December 2025 to November 2026.
Orbital Insertion Timeline and Maneuvers
Entering orbit around Mercury requires an extended series of continuous activities rather than a single burn, according to Montagnon. Following the arrival at Mercury on Nov. 21, the stacked orbiters will undergo 16 maneuvers to progressively lower and reshape their orbit. Subsequent milestones include Mio separating into an elliptical polar orbit around Dec. 9, and the release of Mio’s sunshield on Dec. 16 before the Mercury Planetary Orbiter reaches its final polar orbit on March 10, 2027.
Did you know? Mercury is the least explored rocky planet in the solar system because the sun’s intense gravitational pull accelerates approaching spacecraft, requiring complex gravity assists and thruster burns to capture an orbiter.
Scientific Objectives for the Dual Orbiters
Science operations are scheduled to begin on April 6, 2027, with both probes operating simultaneously from complementary polar orbits. The Mercury Planetary Orbiter will examine the planet’s surface composition, geology, and interior, while Mio will investigate the magnetic field and its interaction with the solar wind, based on mission planning details.
Frequently Asked Questions
When will BepiColombo arrive at Mercury?
Why did the mission experience a delay?
An electric current issue between the transfer module’s solar array and power distribution unit reduced available power for the thrusters in April 2024, requiring a lower-thrust trajectory that shifted arrival to late 2026, according to mission managers.
What are the names of the two science orbiters?
The mission utilizes ESA’s Mercury Planetary Orbiter and JAXA’s Mercury Magnetospheric Orbiter, called Mio.
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