The BepiColombo mission has crossed another major milestone. Engineers confirmed the successful separation of the Mercury Transfer Module (MTM) on September 3, 2026, at approximately 1400 CEST. The jettison was verified through Doppler signal detection, marking the end of the spacecraft's extended cruise phase and the beginning of its final approach to Mercury.
This separation was not originally planned for the December 2025 timeline. The delay to a November 2026 orbit insertion stems from persistent problems with the spacecraft's Solar Electric Power (SEP) system. Those technical issues forced mission planners to rethink the trajectory, extending the cruise phase by nearly a year. The separation now sets the stage for the Mercury Planetary Orbiter (MPO) to enter its final science orbit and begin the primary science phase of the mission.
Spacecraft Specifications and Architecture
The mission architecture features two distinct orbiters designed to study Mercury from complementary vantage points. The Mercury Planetary Orbiter (MPO) has a main body measuring 2.4 x 2.2 x 1.7 meters and a total mass of 1,230 kilograms, including an 85-kilogram science payload. In contrast, JAXA's Mercury Magnetospheric Orbiter (MMO), nicknamed Mio, is smaller with a diameter of 1.8 meters, a height of 1.1 meters, and a mass of 255 kilograms, of which 45 kilograms is dedicated to its science instruments.
- MPO Stabilization: The MPO operates in a 3-axis stabilized, nadir-pointing mode.
- MMO Stabilization: The MMO will be spin-stabilized at 15 rpm, with its spin axis oriented 90 degrees to the Sun.
Orbital Timeline and Final Operations
Following the MMO release, which is scheduled between December 9 and December 10, the MPO will begin moving to its final science orbit ranging from 480 to 1,500 kilometers. Nominal science operations are scheduled to commence in April 2027. The mission's delayed timeline reflects the engineering challenges overcome to ensure the spacecraft's safe arrival, and the coming months will see the two orbiters separate and settle into their respective polar orbits around the innermost planet of the Solar System.
