BepiColombo Arrives at Mercury (Orbit Insertion) Countdown

The mission embarked on its journey following a launch aboard an Ariane 5 ECA rocket from the Guiana Space Centre in October 2018. Designed with a total launch mass of 4,100 kilograms, the spacecraft stack made use of solar-electric propulsion, gravity assists, and precise trajectory maneuvers during its multi-year cruise across the inner Solar System. ESA's module was built by Airbus, while JAXA's orbiter was manufactured by ISAS.

Throughout the interplanetary voyage, the science modules were transported in a stacked configuration attached to the Mercury Transfer Module. The combined spacecraft travelled through deep space for eight years, preparing for the complex sequence of operations required to enter orbit around its target destination.

The mission's arrival sequence commenced on 3 September 2026 with the uncoupling of the transfer module from the remaining spacecraft stack. The Mission Control Team at the European Space Operations Centre in Darmstadt, Germany, gave the go-ahead for the operation after verifying system telemetry. Signals confirmed separation via ground antennas in Cebreros, Spain, and Malargüe, Argentina.

Following orbital entry, the two science orbiters are scheduled to decouple from one another on 9 or 10 December 2026. Once separated, each orbiter will maneuver into its distinct science orbit, characterized by a polar inclination of 90 degrees. Primary scientific operations for the mission are scheduled to begin in April 2027 with a planned duration of one year.

The European orbiter will operate in an orbit with a perihermion altitude of 480 kilometers and an apohermion altitude of 1,500 kilometers. In contrast, the Japanese spacecraft will enter a broader elliptical orbit, featuring a perihermion altitude of 590 kilometers and an apohermion altitude of 11,640 kilometers to perform magnetospheric measurements.

On 15 September 2026, instruments on the European orbiter were powered on together for the first time since transfer module separation. The BELA laser altimeter conducted a 21.5-hour test firing, emitting over 700,000 laser pulses into open space to confirm functional performance. This marked the instrument's first comprehensive test since ground trials back on Earth in 2016.

During the same operational period, the MERTIS spectrometer observed deep space simultaneously through both its planet and calibration ports. The transfer module had previously blocked the planet port throughout the cruise phase. Data analysis of approximately 1 gigabit of returned data revealed no noticeable loss in spectrometer sensitivity compared to ground calibration conducted in 2013.

The optical camera system SIMBIO-SYS also activated its three channels and captured its first image in space during these instrument checkouts. Telemetry confirmed that the camera suite functioned properly, allowing ground teams to proceed with operational fine-tuning ahead of primary scientific mapping.

On 24 September 2026, the European orbiter conducted an 8-minute and 42-second thruster firing to execute its first planned trajectory correction after transfer module separation. Monitored by flight operators at ESOC using the Cebreros antenna, the maneuver delivered an exact velocity adjustment of 11.4 meters per second to align the spacecraft for insertion.

Mission management and project scientists shared spacecraft status updates during press briefings held on 31 August and 9 September 2026 at the Europlanet Science Congress in The Hague. Additional small trajectory correction slots were scheduled leading up to the main orbital insertion sequence to ensure precise targeting.