BepiColombo, a joint endeavor between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA), blasted off from Europe’s Spaceport in Kourou, French Guiana, at 01:45 GMT on October 20, 2018. It will make a seven year cruise to Mercury, the smallest and least explored planet in the inner Solar System, flying by Earth once, Venus twice and Mercury six times before entering orbit.
He was the first to see that an unsuspected resonance is responsible for Mercury’s habit of rotating on its axis three times for every two revolutions it makes around the Sun. He also suggested to NASA how to use a gravity-assist swing-by of Venus to place the Mariner 10 spacecraft in a solar orbit that would allow it to fly by Mercury three times in 1974-5.
BepiColombo is the first European mission to Mercury and is the first to send two spacecraft to make complementary measurements of the planet and its dynamic environment at the same time.
The ESA-built Mercury Transfer Module (MTM) will carry the orbiters to Mercury using a combination of solar electric propulsion and gravity assist flybys, with one flyby of Earth, two at Venus, and six at Mercury, before entering orbit at Mercury in late 2025.
“Congratulations on the successful launch of Ariane 5 carrying BepiColombo, ESA/JAXA joint Mercury exploration mission,” said JAXA President Hiroshi Yamakawa.
“Launching BepiColombo is a huge milestone for ESA and JAXA, and there will be many great successes to come,” added ESA Director General Jan Wörner.
“There is a long and exciting road ahead of us before BepiColombo starts collecting data for the science community,” said Günther Hasinger, ESA Director of Science.
“Endeavors like the Rosetta mission and their ground-breaking discoveries even years after their completion have already shown us that complex science exploration missions are well worth the wait.”
The MPO and Mio orbiters will be able to operate some of their instruments during the cruise phase, affording unique opportunities to collect scientifically valuable data at Venus.
Moreover, some of the instruments designed to study Mercury in a particular way can be used in a completely different way at Venus, which has a thick atmosphere compared with Mercury’s exposed surface.
“BepiColombo is one of the most complex interplanetary missions we have ever flown,” said Andrea Accomazzo, ESA Flight Director for BepiColombo.
“One of the biggest challenges is the Sun’s enormous gravity, which makes it difficult to place a spacecraft into a stable orbit around Mercury. We have to constantly brake to ensure a controlled fall towards the Sun, with the ion thrusters providing the low thrust needed over long durations of the cruise phase.”
Other challenges include the extreme temperature environment the spacecraft will endure, which will range from minus 292 degrees Fahrenheit (minus 180 degrees Celsius) to over 842 degrees Fahrenheit (450 degrees Celsius).
On the MPO orbiter, the wide radiator means the spacecraft can efficiently remove heat from its subsystems, as well as reflect heat and fly over the planet at lower altitudes than ever achieved before.
The eight-sided Mio will spin 15 times a minute to evenly distribute the Sun’s heat over its solar panels to avoid overheating.
“Seeing our spacecraft blast off into space is a moment we have all been waiting for,” said ESA’s BepiColombo project manager Ulrich Reininghaus.
“We have overcome many hurdles over the years, and the teams are delighted to see BepiColombo now on the road to intriguing planet Mercury.”
A few months before arriving at Mercury, the transfer module will be jettisoned, leaving the two science orbiters — still connected to each other — to be captured by Mercury’s gravity.
Their altitude will be adjusted using MPO’s thrusters until Mio’s desired elliptical polar orbit is reached.
Then MPO will separate and descend to its own orbit using its thrusters.
Together the orbiters will make measurements that will reveal the internal structure of Mercury, the nature of the surface and the evolution of geological features — including ice in the planet’s shadowed craters — and the interaction between the planet and the solar wind.
“A unique aspect of this mission is having two spacecraft monitoring the planet from two different locations at the same time,” said ESA’s BepiColombo project scientist Johannes Benkhoff.
“This is really key to understanding processes linked to the impact of the solar wind on Mercury’s surface and its magnetic environment.”
“BepiColombo will build on the discoveries and questions raised by NASA’s MESSENGER mission to provide the best understanding of Mercury and Solar System evolution to date, which in turn will be essential for understanding how planets orbiting close to their stars in exoplanet systems form and evolve, too.”