BepiColombo set to be launched on mid-October

Artist’s impression of the BepiColombo spacecraft at Mercury. Credit: ESA

The first European mission to Mercury, BepiColombo, is projected to be launched in the early morning of 19 October. This is a joint ESA-JAXA mission which will launch onboard of an Ariane 5 rocket from Europe’s Spaceport in Kourou, setting a trio of spacecraft on course for Mercury. 

The spacecraft will travel together: a transfer module will carry the two science orbiters – the ESA Mercury Planetary Orbiter and the JAXA Mercury Magnetospheric Orbiter – using a combination of solar power and electric propulsion, and nine gravity-assist flybys of Earth, Venus and Mercury. 

The Lift-off is scheduled for around 01:45 GMT (03:45 CEST), equivalent to 18 October 22:45 in local time (GFT). The date chosen represents the first option to launch, taking into account some additional, unplanned testing performed in Kourou. The launch window remains open until 29 November. 

BepiColombo in low Earth orbit. Credit: ESA

“We have had a great start to our launch campaign in Kourou, and are on track for launch in less than ninety days,” says ESA’s BepiColombo project manager Ulrich Reininghaus. “We have an incredibly packed schedule, but it is great to see our spacecraft building up together for the final time.” 

Since arriving at the Spaceport in May, many essential preparations have been completed. For example, the spacecraft have been fitted with their protective high-temperature blankets, xenon and nitrogen tanks have been checked, loaded and pressurised, and the deployment tests and final installations of the solar arrays are underway. 

Mercury Transfer Module in space simulator. Credit: ESA

Simulations for key operations have also started at ESA’s operations centre in Darmstadt, Germany (ESOC). Personnel are also practicing non-routine events to be prepared for all eventualities on the journey to Mercury. 

The composite spacecraft ‘stack’ will make the first flyby of Mercury just three years after launch. A number of scientific instruments will be active during the planetary flybys, with the transfer module’s ‘webcams’ offering the potential to capture simple images before the main science camera is operational in Mercury orbit. 

Once separated into their final orbits, the two scientific craft will make complementary measurements of the innermost planet and its environment, from its deep interior to its interaction with the solar wind, to provide the best understanding of Mercury to date. The results will provide insight into how the innermost planet of a solar system forms and evolves close to its parent star. 

Exploded view of the BepiColombo spacecraft components. Credit: ESA

Key points about Mercury: 

Mercury is the inner most planet of the solar system, and its rotation is tidally locked into a 3:2 spin orbit resonance with the Sun. It has a solid terrestrial surface and it is heavily cratered with virtually no atmosphere, a world that superficially it resembles the moon. Its average orbital radius is 0.387 098 AU, having a diameter of 4879.4 km and with a mass of 3,302×1023 kg or 0,055 Earths. 

Structure of Mercury. Wikipedia.

However, the interior of the planet was a surprise in many ways, after the Mariner 10 visit, it was possible to have a good read on the planet´s mass and it was discovered that it has a very large iron core may be due to a giant impact during formation, the planet also has a weak magnetic field which was not expected, also it has weak tectonic activity, due to vertical thrust faulting as the planets cools and shrinks. 

Mariner 10. Credit: NASA

The most recent visit to Mercury was by MESSENGER, which entered orbit on March 18, 2011, while it was Launched on August 3, 2004, discovering water ice at the planet's north pole and mapping the entire planet. Inserting a spacecraft into orbit around Mercury is difficult, because the probe approaching on a direct path from Earth would be accelerated by the Sun's gravity and pass Mercury far too quickly to orbit it. 

Image of Mercury from first MESSENGER flyby. Credit: NASA/JPL

However, employing multiple, consecutive gravity assist, 'swingby' manoeuvres around Venus and Mercury, in combination with minor propulsive trajectory corrections, to gradually slow the spacecraft and thereby minimize propellant needs. So trips to Mercury are long and complex. 

Sources: ESA, Wikipedia,