Mercury forward! The spaceship will pass through the planet in an exciting gravity assist maneuver

Artist’s impression of BepiColombo flying over Mercury on October 1, 2021. The spacecraft performs nine gravitational assistance maneuvers (one from Earth, two from Venus and six from Mercury) before orbiting the innermost planet solar system in 2025. Credit: ESA / ATG medialab

ESA /JAXA The BepiColombo mission to Mercury will make the first of six overflights of its destination planet on October 1, 2021, before entering orbit in 2025.

Right after its last flyby of Venus in August, the spacecraft’s next exciting encounter is with Mercury at 11:34 UTC on October 1 (01:34 CEST on October 2). It will fly over the planet at an altitude of around 200 km, capturing images and scientific data that will give scientists a tantalizing taste of what is to come in the main mission.

The mission includes two scientific orbiters which will be placed in complementary orbits around the planet by the mercury transfer module in 2025. The planetary mercury orbiter led by ESA and the magnetospheric mercury orbiter led by JAXA, Mio, will study all aspects of this mysterious planet from its core to surface processes, magnetic field and exosphere, to better understand the origin and evolution of a planet close to its mother star.

BepiColombo will use nine planetary flyovers in total: one on Earth, two on Venus, and six to Mercury, as well as the spacecraft’s solar electric propulsion system, to help navigate Mercury’s orbit.

On track for the Mercury slingshot

Timeline of overflights during BepiColombo’s 7.2-year journey to Mercury, starting with the nearly two-month launch window opening in October 2018. Credit: ESA

Gravitational overflights require extremely precise deep space navigation work, ensuring that the spacecraft is on the correct approach path.

A week after the last overflight of BepiColombo on August 10, a corrective maneuver was carried out to push the machine a little for this first overflight of Mercury, aiming at an altitude of 200 km. Right now, the craft is expected to pass the innermost planet at 198 km, and small adjustments can easily be made with solar electric propulsion maneuvers after the pass. Since BepiColombo is over 100 million kilometers from Earth and the light takes 350 seconds (about six minutes) to reach it, being on target just two kilometers away is no small feat.

“It is thanks to our remarkable ground stations that we know the whereabouts of our spacecraft with such precision. With this information, the Flight Dynamics team at ESOC knows how much we need to maneuver to be in the right place for Mercury’s gravitational assistance, ”explains Elsa Montagnon, space operations manager for the mission.

“As is often the case, the trajectory of our mission has been planned so meticulously that no further corrective maneuvers are expected for this next overflight. BepiColombo is on the right track.

First glimpse of Mercury

During overflights, it is not possible to take high resolution images with the main science camera as it is protected by the transfer module while the spacecraft is in cruise configuration. However, two of BepiColombo’s three surveillance cameras (MCAMs) will take pictures approximately five minutes after the close approach time and up to four hours later. Because BepiColombo arrives on the night side of the planet, conditions are not ideal for taking images directly at the closest approach, so the closest image will be captured at a distance of approximately 1000 km.

Key moments during BepiColombo’s first flyby of Mercury on October 1, 2021, which will see the spacecraft pass within 200 km of the planet at 11:34 UTC. Credit: ESA

The first image to be uploaded will be approximately 30 minutes after the nearest approach, and should be available for public release around 8:00 a.m. CEST on Saturday morning. The close-up approach and the following images will be broadcast one by one on Saturday morning.

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 solar panels and antennas of the spacecraft. As the spacecraft changes orientation during the flyby, Mercury will be seen to pass behind the structural elements of the spacecraft.

In general, MCAM-2 will point to the northern hemisphere of Mercury, while MCAM-3 will point to the southern hemisphere. For half an hour after the close-in approach, imagery will alternate between the two cameras. Subsequent imaging will be performed by MCAM-3.

For the closest images, it should be possible to identify large impact craters on the planet’s surface. Mercury has a heavily cratered surface much like the appearance of Earth’s Moon, tracing its 4.6 billion year history. Mapping the surface of Mercury and analyzing its composition will help scientists better understand its formation and evolution.

Even though BepiColombo is in a “stacked” cruise configuration for the overflights, it will be possible to use some of the scientific instruments on the two planetary orbiters, which will allow a first glimpse of the magnetic field of the planet, plasma and the particle environment.

“We are really looking forward to seeing the first results of measurements taken so close to the surface of Mercury,” says Johannes Benkhoff, scientist from ESA’s BepiColombo project. “When I started working as a project scientist on BepiColombo in January 2008, NasaThe Messenger mission had its first flyby over Mercury. Now it’s our turn. It’s a fantastic feeling!

Celebrate the namesake of BepiColombo

The first upcoming Mercury flyby marks the 101st anniversary of the birth of Giuseppe ‘Bepi’ Colombo (October 2, 1920 – February 20, 1984), an Italian scientist and engineer named after the BepiColombo mission. Colombo is known to have explained Mercury’s special characteristic of rotating around its own axis three times in two orbits of the Sun. He also realized that by carefully choosing the point of flight of a spacecraft as it passes a planet, the planet’s gravity could help the spacecraft to perform other overflights. Its interplanetary calculations enabled NASA’s Mariner 10 spacecraft to perform three flyovers over Mercury instead of one using a flyby over Venus to alter the spacecraft’s flight path – the first of many spacecraft to use such a gravity assistance maneuver.

BepiColombo, with its two science orbiters, is expected to build on the accomplishments of NASA’s Messenger mission, to provide the best understanding of the solar system’s innermost planet to date. This graph highlights some Messenger findings and shows how BepiColombo will follow up. Credit: ESA

Following the Mariner 10 mission in 1974-75, NASA’s Messenger spacecraft flew over Mercury three times in 2008-09 and circled the planet for four years (2011-2015). The BepiColombo mission will build on the successes of its predecessors to provide the best understanding of the solar system’s innermost planet to date.

The first image should be published early in the morning of Saturday October 2 (tentatively at 8:00 a.m. CEST); the following images may be shown later today on Saturday and / or Monday, October 4. Additional scientific commentary may also be available within a week of the flyby. Schedules may change based on actual spaceship events and image availability.