The ESA/JAXA BepiColombo mission is gearing up for its second close-up of Mercury on June 23. ESA’s spacecraft operations team guides BepiColombo through six of the planet’s gravity aids before orbiting it in 2025.
Like its first encounter last year, this week’s flyby will also take the spacecraft to an altitude of about 200 km above the Earth’s surface. Closest approach is expected at 09:44 UT (11:44 CEST).
The primary purpose of the flyby is to use the planet’s gravity to fine-tune BepiColombo’s orbit. Launched into space in October 2018 on an Ariane 5 from the European spaceport in Kourou, BepiColombo uses nine planetary flybys: one on Earth, two on Venus and six on Mercury, along with the spacecraft’s electric solar propulsion system, to help steer Mercury’s orbit against the massive gravitational pull of our sun.
While BepiColombo is in a ‘stacked’ cruise configuration for these short flybys, meaning many instruments are not yet fully operable, it could still pick up an incredible taste of Mercury science to advance our understanding and knowledge of the Solar System’s innermost planet. enlarge. A series of snapshots will be taken by BepiColombo’s three surveillance cameras showing the planet’s surface, while some of its magnetic, plasma and particle surveillance instruments will sample the environment both near and far from the planet in the hours surrounding its near approach.
“Even during fleeting flybys, these scientific ‘grips’ are extremely valuable,” said Johannes Benkhoff, ESA’s BepiColombo project scientist. “We get to fly our world-class science lab through diverse and unexplored parts of Mercury’s environment that we won’t have access to once we’re in orbit, while also getting a head start on preparations to ensure that we move on to the main science mission as quickly and smoothly as possible.”
A unique aspect of the BepiColombo mission is the dual nature of spacecraft. The ESA-led Mercury Planetary Orbiter and the JAXA-led Mercury Magnetospheric Orbiter, Mio, will be launched into complementary orbits around the planet by a third module, ESA’s Mercury Transfer Module, in 2025. Together they will study all aspects of this mysterious inner planet from its core to surface processes, magnetic field and exosphere, to better understand the origin and evolution of a planet close to its parent star. Dual observations are key to understanding solar wind-driven magnetospheric processes, and BepiColombo will break new ground by providing unparalleled observations of the planet’s magnetic field and the interaction of the solar wind with the planet at two different locations simultaneously.
On course for catapult
Gravity flights require extremely precise deep space navigation work to ensure that a spacecraft passes the massive body that will change its orbit at just the right distance, angle and speed. All this is calculated years in advance, but must be as perfect as possible on the day itself.
Getting into orbit around Mercury is a challenging task. First, BepiColombo had to shed the orbital energy it was “born” with when launched from Earth, meaning it first flew into a similar orbit to our home planet — shrinking its orbit to a size more closely resembling Mercury’s. Thus, BepiColombo’s first flybys of Earth and Venus were used to ‘dump’ energy and fall closer to the center of the solar system, while Mercury’s series of flybys are used to lose more orbital energy, but now with the aim of to be caught by the scorched planet.
For this second of six such flybys, BepiColombo must pass Mercury only 200 km from the surface, at a relative speed of 7.5 km/s. In doing so, BepiColombo’s speed relative to the sun is slowed by 1.3 km/s, bringing it closer to Mercurial’s orbit.
“We have three slots available to perform correction maneuvers from ESA’s ESOC Mission Control in Darmstadt, Germany, to be in the right place at just the right time to use Mercury’s gravity when we need it,” explains Elsa Montagnon , Mission Manager for Bepi Colombo.
“The first such slot was used to match the desired flight altitude of 200 km above the surface of the planet so that the spacecraft would not come on a collision course with Mercury. Thanks to the painstaking work of our Flight Dynamics colleagues, this first trajectory correction was done very accurately, so that further slots were not necessary.”
Selfie cam is ready
During the flybys, it is not possible to capture high-resolution images with the main science camera, as it is shielded by the transfer module while the spacecraft is in cruise configuration. However, BepiColombo’s three surveillance cameras (MCAMs) will take pictures.
Because BepiColombo’s closest approach will be on the night side of the planet, the first images in which Mercury will illuminate are expected to be about five minutes after the close approach, at a distance of about 800 km.
The cameras provide black-and-white photos at a resolution of 1024 x 1024 pixels and are positioned on the Mercury Transfer Module in such a way that they also capture the spacecraft’s solar panels and antennas. As the spacecraft changes direction in flight, Mercury will be seen passing behind the spacecraft’s structural elements.
The first images are downlinked within a few hours of the closest approach; the first is expected to be available for public release in the afternoon of June 23. Subsequent images will be downlinked throughout the day and a second image release, consisting of multiple new images, is expected Friday morning. All images are scheduled to be released to the public on Monday, June 27 at the Planetary Science Archive.
For the closest images, it should be possible to identify large impact craters and other prominent geological features associated with tectonic and volcanic activity, such as escarpments, ripple ridges and lava plains on the Earth’s surface. Mercury’s heavily cratered surface records a 4.6 billion-year history of asteroid and cometary bombardments, which, along with unique tectonic and volcanic curiosities, will help scientists unravel the secrets of the planet’s place in the evolution of the solar system.
Follow the flyby
The timing of image releases is subject to change depending on actual spacecraft events and image availability.
For more information, please contact:
ESA Media Relations