BepiColombo Swings by Mercury for the 6th Time
Closest Approach Came at 0200 EDT This Morning
The ESA/JAXA BepiColombo mission soared just 183 miles above Mercury's surface this morning, with the closest approach happening at 06:59 CET (05:59 UTC/02:00 EST). This opportunity allowed the spacecraft to photograph Mercury, make unique measurements of the planet’s environment, and fine-tune science instrument operations before the main mission begins. This sixth and final flyby will reduce the spacecraft’s speed and change its direction, readying it for entering orbit around the tiny planet in late 2026.
“We can't wait to see what BepiColombo will reveal during this sixth and final flyby of Mercury."
Geraint Jones, ESA
BepiColombo is more than six years into its eight-year journey to planet Mercury. In total, it is using nine planetary flybys to help steer itself into orbit around the small rocky planet: one at Earth, two at Venus, and six at Mercury. Making the most of this sixth close approach to the small rocky planet, BepiColombo's cameras and various scientific instruments will investigate Mercury's surface and surroundings.
BepiColombo approached on the night side of the planet. Its monitoring cameras were expected to get the most interesting views of Mercury’s surface as the spacecraft comes around to the planet's sunlit side, from about 07:06 CET, seven minutes after the closest approach. The first images are expected to be transmitted to Earth Thursday, with other scientific data to follow.
“We can't wait to see what BepiColombo will reveal during this sixth and final flyby of Mercury. While we're still two years away from the mission's main science phase, we expect this encounter to provide us with beautiful images and important scientific insights into the least-explored terrestrial planet,” said Geraint Jones, ESA's BepiColombo Project Scientist.
While Mercury's sunlit side is scorching, the first part of the upcoming flyby will be spent on Mercury's cold, dark night side. While in Mercury's shadow, BepiColombo will not receive any direct sunlight for more than 23 minutes and will rely only on its batteries.
Mission operators at the European Space Operations Centre (ESOC) are gearing up for this critical moment of the flyby. One day ahead of the eclipse, they will warm up the spacecraft and only stop the heating a few minutes before BepiColombo enters Mercury's shadow. This operation will help save battery power by ensuring that the spacecraft does not need to use its heaters during the eclipse.
"This is the first time BepiColombo stays in the shadow of Mercury for so long," said Ignacio Clerigo, BepiColombo's Spacecraft Operations Manager.
The Italian Spring Accelerometer (ISA) recorded the accelerations felt by the spacecraft as it experienced not only the gravitational pull of the planet, but also the change in solar radiation and temperature as the spacecraft entered and exited Mercury's shadow. ISA was also programmed to record any movements and vibrations of the spacecraft caused by the motion of, for example, the spacecraft's solar arrays.
Excitingly, BepiColombo's route flew over Mercury's north pole, allowing the spacecraft to peer down into craters whose insides never get touched by the Sun. Despite temperatures reaching 450 °C on Mercury's sunlit surface, the polar ‘permanent shadow regions’ are literally ice-cold.
Data gathered by instruments on NASA’s Messenger spacecraft between 2011 and 2015, plus radar observations from Earth, have provided strong evidence for water ice in some of these craters. Whether there is really water ice on hot Mercury is one of the top five mysteries that BepiColombo has set out to solve.
During this flyby, it was hoped that BepiColombo's monitoring camera 1 (M-CAM 1) would get some nice views of the permanently shadowed Prokofiev, Kandinsky and Tolkien craters, as well as the deep Stieglitz and Gaudí craters, Mercury's largest impact crater (the more than 1500 km-wide Caloris Basin), and the vast northern plains known as Borealis Planitia.