BepiColombo completes fourth Mercury flyby

BepiColombo completes fourth Mercury flyby
by Erica Marchand
Paris, France (SPX) Sep 06, 2024
The ESA/JAXA BepiColombo mission successfully carried out its fourth of six gravity assist flybys at Mercury, capturing critical data and views of two distinct impact craters. These flybys utilize Mercury's gravity to steer the spacecraft for its final arrival in orbit around the planet in November 2026.

The closest approach occurred on 4 September 2024 at 23:48 CEST (21:48 UTC), with BepiColombo coming within 165 km of the planet's surface. This marked the first time the spacecraft had a clear view of Mercury's south pole.

"The main aim of the flyby was to reduce BepiColombo's speed relative to the Sun, so that the spacecraft has an orbital period around the Sun of 88 days, very close to the orbital period of Mercury," said Frank Budnik, BepiColombo Flight Dynamics Manager. "In this regard, it was a huge success, and we are right where we wanted to be at this moment. But it also gave us the chance to take photos and carry out science measurements, from locations and perspectives that we will never reach once we are in orbit."

BepiColombo's three monitoring cameras captured various angles of Mercury's surface as the spacecraft flew from the planet's 'nightside' toward the sunlit side. The M-CAM 2 camera provided particularly striking views, revealing more detail as BepiColombo moved into sunlight. M-CAM 3 contributed an additional image of a recently named crater.

At four minutes past the closest approach, the spacecraft came into view of a large peak ring basin, Vivaldi, named after the composer Antonio Vivaldi. Measuring 210 km across, this crater showed striking shadows and a gap in its ring, indicating that lava flows had flooded the crater floor.

Shortly after, another significant peak ring basin, recently named Stoddart after New Zealand artist Margaret Olrog Stoddart, came into view. This crater, measuring 155 km across, holds potential interest for future studies. "When we were planning for this flyby, we saw that this crater would be visible and decided it would be worth naming due to its potential interest for BepiColombo scientists in the future," said Professor David Rothery of The Open University.

BepiColombo's monitoring cameras captured valuable views of these craters, showing signs of the planet's long history of bombardment by asteroids and comets. These snapshots provide a preview of the scientific work to come when BepiColombo enters Mercury's orbit in 2026.

Currently, the spacecraft's science instruments are in partial operation as it remains in its 'stacked' cruise configuration. However, they were active during this flyby, collecting important data on the magnetic, plasma, and particle environment that will be inaccessible once in orbit.

"BepiColombo is only the third space mission to visit Mercury, making it the least-explored planet in the inner Solar System," explained Jack Wright, ESA Research Fellow and M-CAM imaging team coordinator. "The images and science data collected during the flybys offer a tantalising prelude to BepiColombo's orbital phase, where it will help to solve Mercury's outstanding mysteries."

Following this fourth flyby, BepiColombo is scheduled for two more gravity assists on 1 December 2024 and 8 January 2025, further aligning its path for orbit insertion around Mercury in November 2026.

All M-CAM images from this flyby will be publicly available in the Planetary Science Archive from 13 September 2024.