BepiColombo Performed its Fifth Mercury Flyby

Today at 15:23 CET, BepiColombo flew 37,360 km above the surface of Mercury, marking the fifth time the spacecraft has performed a flyby of the planet.

Mercury in motion… One of the #BepiColombo selfie-cameras captured Mercury today as the spacecraft rushed by the planet at almost 3 km per second. 🛰️💨
This time-lapse of unprocessed images was captured during 10:26-11:18 UTC today (11:26-12:18 CET), between 53700 and 48000 km… pic.twitter.com/NPlnLCBOr3

— BepiColombo (@BepiColombo) December 1, 2024

Despite the distance from Mercury’s surface being much greater than during previous flybys (~200 km), this was the first time BepiColombo used the MERTIS radiometer and thermal infrared spectrometer to study how much the planet emits in the mid-infrared wavelengths of light. The data MERTIS collected during the flyby will be sent to the ground stations on Earth between today and tomorrow and will help the scientists reveal what types of minerals the planet’s surface is made of.

During this flyby, several instruments were activated: the magnetometers MPO-MAG and MMO-MGF, the MGNS gamma-ray and neutron spectrometer, the SIXS X-ray and particle spectrometer, the MDM dust monitor, and the PWI instrument, which measures electric fields, plasma waves, and radio waves.

About the mission: long-duration cruise and nine flybys

BepiColombo, named after Prof. Giuseppe “Bepi” Colombo, who first designed an interplanetary gravity assist for the Mariner 10 mission, is a joint mission between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) to study the planet Mercury.

The mission lifted off from French Guiana aboard an Ariane 5 rocket on October 20, 2018, and is expected to enter Mercury’s orbit in November 2026.

The spacecraft consists of two orbiters: the Mercury Planetary Orbiter (MPO), developed by ESA, and the Mercury Magnetospheric Orbiter (MMO), developed by JAXA.

BepiColombo’s mission is divided into two main phases: the cruise phase and the Mercury phase. During the cruise phase, the two orbiters travel together as part of a composite structure known as the Mercury Composite Spacecraft (MCS). This composite includes a propulsion module, the Mercury Transfer Module (MTM), and a sun shield (MOSIF) to protect the MMO’s instruments.

During the cruise, the satellite performs nine flybys around the Earth, Venus, and Mercury, while adjusting its interplanetary trajectory using the four T6 solar electric propulsion thrusters it has on board.

Once in Mercury’s orbit, MPO and MMO will separate and the sixteen payloads will perform several studies such as the investigation of Mercury’s exosphere and magnetosphere, and a study of Mercury’s form, interior, structure, geology, composition, and craters.

Due to the vicinity with the Sun and the low gravity of Mercury, the payloads will be able to operate for one or two years only.

^{Cover image: a picture of Mercury taken by BepiColombo during its fourth flyby of the planet in September 2024. Credits: ESA}