The ESA/JAXA BepiColombo mission is preparing for its second close flyby of Mercury on June 23. ESA’s Spacecraft Operations Team guides BepiColombo through six gravitational assists of the planet before entering orbit around it in 2025.
Like its first encounter last year, this week’s flyby will also take the spacecraft about 200 km above the planet’s surface. The closest approach is scheduled for 09:44 UT (11:44 CEST).
The main objective of the flyby is to use the gravity of the planet to refine the trajectory of BepiColombo. After being launched into space on an Ariane 5 from the European spaceport of Kourou in October 2018, BepiColombo uses nine planetary flybys: one on Earth, two on Venus and six on Mercury, as well as the solar electric propulsion system of the spacecraft, to help navigate Mercury’s orbit against the enormous gravitational pull of our Sun.
Even though BepiColombo is in “stacked” cruise configuration for these brief flybys, which means that many instruments cannot yet be fully exploited, it can still capture an incredible taste of Mercury science to enhance our understanding and knowledge. of the innermost planet in the solar system. A sequence of snapshots will be taken by BepiColombo’s three surveillance cameras showing the planet’s surface, while a number of magnetic, plasma and particle surveillance instruments will sample the environment both near and far from the planet. planet in the near hours.
“Even in short-lived flybys, these scientific ‘apprehensions’ are extremely valuable,” says Johannes Benkhoff, ESA’s BepiColombo project scientist. “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 move on to the main scientific mission. as quickly and easily as possible.
A unique aspect of the BepiColombo mission is its dual spacecraft nature. The ESA-led Mercury Planetary Orbiter and the JAXA-led Mercury Magnetospheric Orbiter, Mio, will be delivered to complementary orbits around the planet by a third module, ESA’s Mercury Transfer Module, in 2025 Working 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-induced magnetospheric processes, and BepiColombo will break new ground by providing unparalleled observations of the planet’s magnetic field and the solar wind’s interaction with the planet at two different locations at the same time.
On the way to the slingshot
Gravity flybys require extremely precise navigation work in deep space, ensuring that a spacecraft passes the massive body that will alter its orbit at the right distance, at the right angle and with the right speed. All of this is calculated years in advance but must be as perfect as possible on the day.
Getting into orbit around Mercury is a difficult task. BepiColombo first had to shed the orbital energy it was “born” with when launched from Earth, meaning it first flew in a similar orbit to our home planet – and reduced its orbit to a size more similar to that of Mercury. The first flybys of Earth and Venus by BepiColombo were therefore used to “spill” energy and get closer to the center of the solar system, while the series of Mercury flybys are used to lose more orbital energy, but now for the purpose of being captured by the scorched planet.
For this second of six flybys of this type, BepiColombo must pass Mercury just 200 km from its surface, with a relative speed of 7.5 km/s. By doing so, BepiColombo’s speed relative to the Sun will be slowed by 1.3 km/s, bringing it closer to Mercurial’s orbit.
“We have three slots available to perform corrective maneuvers from ESA’s ESOC Mission Control in Darmstadt, Germany, to be in precisely the right place at the right time to use Mercury’s gravity as we need it. “, explains Elsa Montagnon, mission manager for BepiColombo.
“The first such slot was used to set the desired flyby altitude of 200 km above the planet’s surface, ensuring the spacecraft would not be on a collision course with Mercury. Thanks to the meticulous work of our colleagues at Flight Dynamics, this first trajectory correction was executed with great precision, so that further slots were not necessary.
Selfie-cam is gone
During flybys, it is not possible to take high resolution images with the main science camera because it is shielded by the transfer module when the spacecraft is in cruise configuration. However, the three surveillance cameras (MCAM) of BepiColombo will take pictures.
Since the closest approach to BepiColombo will be from the night side of the planet, the first images in which Mercury will be illuminated should be around five minutes after the close approach, at a distance of around 800 km.
The cameras provide black and white snapshots with a resolution of 1024 x 1024 pixels and are positioned on the mercury transfer module so as to also capture the spacecraft’s solar panels and antennas. As the spacecraft changes orientation during the flyby, Mercury will be seen to pass behind structural elements of the spacecraft.
The first images will be redirected a few hours after the closest approach; the first should be available for public release on the afternoon of June 23. Subsequent images will be downlinked throughout the day and a second image release, including several new images, is expected by Friday morning. All images are scheduled to be made public in the Planetary Science Archive on Monday, June 27.
For closer images, it should be possible to identify large impact craters and other significant geological features related to tectonic and volcanic activity such as scarps, ridges and lava plains on the surface of the planet. Mercury’s heavily cratered surface records a 4.6 billion year history of asteroid and comet bombardment, which, together with unique tectonic and volcanic sights, will help scientists unlock the secrets of the planet’s place in the evolution of the solar system.
Follow the flyover
Image release times are subject to change based on actual spacecraft events and image availability.
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