BepiColombo: ESA-JAXA Spacecraft Set For First Close Encounter With Mercury On Special Day

After its rendezvous with Venus in August as part of an incredible double Venus flyby by two space probes 33 hours apart, the BepiColombo spacecraft is on course to fly past Mercury at a distance of only about 200 km at 23:34 UTC (Coordinated Universal Time) on 1 October.

In Indian time, the close encounter will occur at 05:04 on Saturday, 2 October. The day of the flyby marks the birth anniversary of Italian scientist, mathematician, and engineer Giuseppe “Bepi” Colombo, after whom the spacecraft and mission are named.

ESA describes him as the “grandfather of the fly-by”. Colombo’s calculations enabled the Mariner 10 spacecraft of the National Aeronautics and Space Administration (NASA) — the first spacecraft sent to study Mercury — to accomplish three Mercury flybys instead of one by piggybacking on a Venus flyby in the 1970s.

On 2 October, the BepiColombo spacecraft will arrive on the planet’s nightside. According to ESA, two of three monitoring cameras on board will take pictures starting from five minutes after the closest approach till up to four hours later. Because of night-time conditions, the closest photographic capture of the planet from the spacecraft will be when it is 1,000 km away.

The release of the first image of the encounter to the public can be expected at 11:30 am (Indian Standard Time) on Saturday, 2 October. Subsequent images will follow in a trickle later in the day and/or on Monday, 4 October. The pictures will be black-and-white snapshots in 1024 x 1024 pixel resolution.

BepiColombo is Europe’s first mission to Mercury. It is a collaboration between the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA). Each agency has a dedicated orbiter on the mission, Mercury Planetary Orbiter (ESA) and the Mercury Magnetospheric Orbiter (JAXA), that will be delivered into complementary orbits around the planet by the Mercury Transfer Module in 2025.

The upcoming Mercury flyby will be the first of six scheduled for BepiColombo and, according to ESA, will help scientists get pictures and science data as “a tantalising first taste of what’s to come in the main mission”.

The gravitational pull of planets, such as Mercury in this case, is smartly used to alter the speed and direction of spacecraft so they can be steered precisely towards their destination. In the process, planetary flybys provide data that can help scientists better understand the environment of the planet in question.

Some scientific instruments on BepiColombo may be called on to gather data pertaining to Mercury’s magnetic, plasma, and particle environment, ESA notes.

On 10 August, BepiColombo flew past Venus, Mercury's neighbour, at a distance of 552 km. All three monitoring cameras on board the Mercury Transfer Module took numerous pictures. ESA even provided a glimpse of the “sights and sounds” of the flyby.

A small intervention by the ESA a week later helped the spacecraft to be right on course for its planned 1 October Mercury flyby.

BepiColombo took off on a seven-year journey towards Mercury in October 2018. It swung by Earth in April 2020 and then zoomed past Venus twice, once in October 2020 and then on 10 August 2021. Now it gears up for its first Mercury flyby.

These flybys, in addition to the services of the solar electric propulsion system on board the spacecraft, will take BepiColombo into Mercury orbit in 2025 while resisting the strong gravitational pull of the Sun.

Mercury sits closest to the Sun. Aged 4.6 billion years, it is the smallest of all planets and happens to be the least-explored terrestrial planet in our solar system. However, NASA’s Mariner and MESSENGER missions have inspired new missions to the planet to explore it further.

BepiColombo has a mission duration of one year around Mercury with a possible extension of one year. During this time, the ESA and JAXA orbiters will work as a team to collect and transmit important data back to Earth.

The data will be able to feed insights on the birth and evolution of a planet living close to its parent star and provide answers to top Mercury mysteries.