The Mercury Planetary Orbiter (MPO) of the BepiColombo mission during launch preparations at Europe’s Spaceport. Credit: ESA - S. Corvaja 

The date is set and marked on the calendar ... to orbit Mars October 18. 

The joint ESA-JAXA BepiColombo mission will launch on an Ariane 5 from Europe’s Spaceport in Kourou, setting a trio of spacecraft on course for Mercury.

Lift-off of the Mercury Planetary Orbiter is anticipated for around 01:45 GMT (03:45 CEST), equivalent to October 18 22:45 in local time (GFT). 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.

What makes this mission so different is that most of ESA's previous interplanetary missions have been to relatively cold parts of the Solar System. BepiColombo will be the Agency's first experience of sending a planetary probe close to the Sun.

This was not a random date. 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 November 29.

BepiColombo at Mercury

ESA’s BepiColombo project manager Ulrich Reininghaus said that they have had a great start to their launch campaign in Kourou, and are on track for launch in less than ninety days. They have an incredibly packed schedule, but it is great to see their 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 pressurized, and the deployment tests and final installations of the solar arrays are underway.

Simulations for key operations have also started at ESA’s operations center in Darmstadt, Germany. 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.