WASHINGTON — The European Space Agency is adjusting the trajectory of its BepiColombo mission to Mercury, delaying its insertion into orbit around the innermost planet by nearly a year to compensate for reduced performance from its electric thrusters.
The spacecraft will pass just 165 kilometers from Mercury’s on this flyby, 35 kilometers closer than previously planned.
The change is part of a revised trajectory for the mission after ESA discovered a problem with the spacecraft’s thrusters in April.
When controllers turned on the thrusters then for a maneuver, they found that the thrusters were not getting enough power.
An investigation found what ESA called “unexpected electric currents” between solar arrays on one part of BepiColombo, the Mercury Transfer Module (MTM), and a power distribution unit.
Those currents reduced the power available for the electric thrusters and prevent the mission from carrying out its original trajectory.
“Following months of investigations, we have concluded that MTM’s electric thrusters will remain operating below the minimum thrust required for an insertion into orbit around Mercury in December 2025,” Santa Martinez, BepiColombo mission manager at ESA, said in a statement.
While BepiColombo will go into orbit 11 months later than planned, ESA said the change won’t affect overall mission science.
BepiColombo’s main camera will not operate during the flyby since its view is blocked while in cruise mode.
However, three engineering cameras will take images of Mercury during the flyby, including the first views of the planet’s south pole.
WASHINGTON — To make up for decreased performance from its electric thrusters, the European Space Agency is changing the course of its BepiColombo mission to Mercury, postponing its entry into orbit around the innermost planet by almost a year.
The ESA declared on September. 2 that the spacecraft, which is part of a joint mission with the Japanese space agency JAXA, will fly by Mercury on September 2 on a slightly different trajectory. The spacecraft launched in 2018 and has since completed several flybys of the Earth, Venus, and Mercury. 4. . This flyby will bring the spacecraft just 165 kilometers—35 kilometers closer than originally anticipated—from Mercury.
The modification is a part of the mission’s reroute, which was made after ESA identified a thruster issue with the spacecraft in April. The thrusters were not receiving enough power when the controllers turned them on for a maneuver. In December 2025, the thrusters needed to be maneuvered to get the spacecraft into orbit around Mercury. Despite this, the thrusters could only be restored to 90% of their original capacity by the engineers.
Following an investigation, the Mercury Transfer Module (MTM), a power distribution unit, and solar arrays on one section of BepiColombo were found to have “unexpected electric currents,” according to ESA. The mission cannot follow its original trajectory because of those currents, which decreased the power available for the electric thrusters.
BepiColombo mission manager at ESA Santa Martinez said in a statement, “After months of investigation, we have concluded that MTM’s electric thrusters will remain operating below the minimum thrust required for an insertion into orbit around Mercury in December 2025.”.
The upcoming flyby—the fourth of six scheduled for the mission—as well as the next two in December and January are all included in the alternative mission profile that the mission developed. To make up for the decreased thrust, the spacecraft will fly a different trajectory, which will cause it to enter orbit later—in November 2026 as opposed to December 2025.
The overall mission science will not be impacted, according to ESA, even though BepiColombo will launch 11 months later than anticipated. Ten of the spacecraft’s instruments will be gathering data during the next flyby, giving science teams the opportunity to assess how well they are working while also gathering information from parts of the planet and the magnetosphere that won’t be explored once the spacecraft is in orbit.
The mission’s project scientist, Johannes Benkhoff, said in a statement, “We get to fly our world-class science laboratory through diverse and unexplored parts of Mercury’s environment that we won’t have access to once in orbit, while also getting a head start on preparations to make sure we will transition into the main science mission as quickly and smoothly as possible.”.
Because it is in cruise mode and its view is obscured, BepiColombo’s primary camera will not function during the flyby. Three engineering cameras, however, will capture pictures of Mercury during the flyby, including the first looks at the planet’s south pole.
