The Mercury-bound BepiColombo probe took a second look at its target planet today during a very close flyby designed to slow the spacecraft and adjust its trajectory.
BepiColombo is a joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA). The mission, consisting of two orbiters traveling to Mercury stacked on top of each other, spear orbiting the sun in 2018. Since then, ground controllers have adjusted the spacecraft’s trajectory through a series of nine hover maneuvers (one on Earth, two on Venus, and six on Mercury itself), to slow gradually BepiColombo so that it can enter orbit around the solar systeminnermost planet in 2025.
The June 23 flyby was BepiColombo’s second to Mercury, after that of the probe first encounter with the planet in October 2021. The probe made its closest approach to Mercury’s surface at 5:44 a.m. EDT (0944 GMT), when it passed just 200 kilometers from Mercury’s crater-riddled surface, closer that both orbiters will only work once the mission begins in earnest.
Related: Mercury looks stunning in this first flyby photo of Europe and the Japanese BepiColombo mission
The probe was taking images of the scorched planet during the flyby with its low-resolution surveillance cameras that are mounted on the spacecraft’s transfer module. ESA released the first image about four hours after the closest approach, revealing large impact craters, including a 120-mile-wide (200 km) basin.
The two orbiters together carry 16 science instruments, but only about 60% of them were operational for the 48 hours around the closest approach, ESA’s BepiColombo project scientist Johannes Benkhoff told Space. com in an email. The rest, including the high-resolution cameras, cannot be used in the cruise configuration, as they are hidden either by the spacecraft’s transfer module or its sun visor.
Benkhoff said the spacecraft’s magnetometers and particle detectors were turned on during the flyby and will likely generate valuable scientific data about the solar wind near Mercury.
During this flyby, BepiColombo approached Mercury from the night side, Benkhoff noted, meaning that imaging could not begin until 4 minutes after the closest approach, when the planet was sufficiently illuminated. At that time, the probe was about 800 km from the surface of Mercury.
The images, which the ESA expects to release within about a day, are expected to reveal craters and tectonic faults on Mercury’s sun-scorched surface.
“Even in fleeting flybys, these scientific ‘grabs’ are extremely valuable,” Benkhoff said in an ESA. statement (opens in a new tab). “We can 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 getting a head start on preparations to ensure that we will transition to the primary science mission as quickly and easily as possible.”
BepiColombo is only the second probe in history built to orbit Mercury, after NASA’s Messenger mission, which studied the tiny rocky planet between 2011 and 2015. (Although in the 1970s NASA Sailor 10 performed three flybys of Mercury while in orbit around the Sun and took the very first images of the planet).
Mercury is a strange world where temperatures reach up to 800 degrees Fahrenheit (420 degrees Celsius) in parts exposed to the sun, but where, at the same time, scientists believe frozen water lingers in permanently shadowed craters around the poles.
Mercury, although geologically dead at first glance, also shows hints of some form of tectonic activityand wears a surprising magnetic field that scientists so far cannot fully explain. Many of these mysteries have been uncovered by Messenger, and scientists are hoping BepiColombo will provide the missing answers.
BepiColombo has four more flybys to complete before finally settling into orbit around Mercury. The next flyby will take place in about a year. Meanwhile, next month, BepiColombo will make the closest approach to the sun of its entire mission.
Reaching Mercury is notoriously difficult, harder than reaching the distant giant planets Jupiter and Saturn. The reason is that the sun gravity constantly accelerating any probe bound to Mercury, which needs to lose energy and speed – hence the long and winding journey of planetary flybys.