Meeting Mercury

A beautiful sequence of 53 images taken by the monitoring cameras on board the ESA/JAXA BepiColombo mission as the spacecraft made its first close flyby of its destination planet Mercury on 1 October 2021.
The compilation includes images from two of the three Monitoring Cameras (MCAM) onboard the Mercury Transfer Module, which provides black-and-white snapshots at 1024 x 1024 pixel resolution. It is not possible to image with the high-resolution camera suite during the cruise phase. The MCAMs also capture parts of the spacecraft: MCAM-2 sees the medium-gain antenna and magnetometer boom, while the high-gain antenna is in the MCAM-3 field-of-view.

The sequence opens with the closest images acquired by MCAM-2 and MCAM-3, taken at a distance of around 1000 km from the surface of the planet. Closest approach at 199 km took place about five minutes earlier, at 23:34:41 UTC.

During the half hour following the close approach, imaging alternated between the two cameras. In general, MCAM-2 pointed towards the northern hemisphere of Mercury, while MCAM-3 pointed towards the southern hemisphere. Thus the subsequent images show a set of complementary views from each camera in turn, ranging from a distance of about 2420 km to 6140 km from the surface of Mercury. In these relatively close images, it is possible to identify prominent impact craters, scarps, and other geological features that BepiColombo will study in more detail once in orbit around the planet at the end of 2025.

The final part of the compilation illustrates BepiColombo's departure from Mercury as the spacecraft changed attitude along its trajectory, giving the impression Mercury's apparent movement changes direction. The final image was taken at 03:03:49 UTC on 2 October from a distance of approximately 93 thousand kilometres. The final departure sequence has been speeded up by a factor of about 900.

Several different exposure times were used throughout the imaging sequence in order to try and capture the rapidly-varying brightness of Mercury, and in some cases the spacecraft and/or the planet are overexposed, particularly in the final departure sequence. Optical and electronic artefacts are also visible in some images.
The gravity assist manoeuvre was the first at Mercury and the fourth of nine flybys overall. During its seven-year cruise to the smallest and innermost planet of the Solar System, BepiColombo makes one flyby at Earth, two at Venus and six at Mercury to help steer it on course to arrive in Mercury orbit in 2025. The Mercury Transfer Module carries two science orbiters: ESA’s Mercury Planetary Orbiter and JAXA’s Mercury Magnetospheric Orbiter. They will operate from complementary orbits to study all aspects of mysterious Mercury 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.

Credit: ESA/BepiColombo/MTM, CC BY-SA 3.0 IGO; Music composed and performed by Anil Sebastian and Ingmar Kamalagharan.