Mission to Mercury Launches – Sky & Telescope

The spaceship BepiColumbo, a joint Euro-Japanese mission to Mercury, has moved away from Earth to begin its seven-year journey to the deepest planet.

BepiColumbo launches at the top of an Ariane 5 rocket, still in this video.
ESA / CNES / Arianespace

We return to Mercury! . . .finally.

The BepiColombo Space Shuttle was launched on October 19 at 21:45:28. EDT, at the top of an Ariane 5 rocket from an equatorial launch site in Kourou, French Guiana, embarking on a seven-year trip to Mercury. The journey began perfectly, at the top of pillars of flames that illuminated the early morning sky and remained visible until the side-boosts were extinguished 2 minutes later, leaving the continuous light of the main stage of the rocket visible as a greenish dot in the sky.

BepiColombo's journey will bring him back to Earth, twice before Venus and six times with Mercury before finally settling into orbit on December 5, 2025. The mission is a combined effort of the European Space Agency (ESA). ) and Japanese aerospace exploration. Agency (JAXA).

Questions to answer

Mercury seen by the Messenger spacecraft on January 14, 2008, about 27,000 km from the planet.
NASA / APL / Carnegie Institution for Science

Getting to Mercury is difficult – so difficult that fewer spaceships have visited Mercury than Saturn. NASA sent two spacecraft: Mariner 10, which made three overflights (in the same hemisphere) in 1974 and 1975, and Messenger, which fulfilled its orbital mission from 2011 to 2015.

Messenger was one of NASA's low-cost Discovery missions. He accomplished a lot with his reduced payload, producing a world map as well as more detailed maps of topography and composition in the northern hemisphere. (The elliptical orbit of the spacecraft has moved away from the southern hemisphere to allow detailed mapping.) Messenger has discovered Mercury's magnetic field and the tenuous cloud of light. atoms that fly in the space around the planet, confirmed the presence of ice at the poles and identified locations with relatively recent geological activity. But that left us with more new questions than answers to old questions – as should any good fact-finding mission.

How can a terrestrial planet with the largest iron core get so little iron in its crust? Why is his kernel so big? How can its crust be so much sulfur when it is the closest planet to the sun? Why is his magnetic field shifted north of the center of the planet? Why do some craters of Mercury have dark rays and other bright ones? What process has formed the strange characteristics of Swiss cheese called "hollow"?

Two spaceships in one

BepiColombo before transfer to the final assembly building. The magnetospheric mercury orbiter of the JAXA is visible at the top of the stack, the ESA mercury planetary orbitator in the middle and the ESA mercury transfer module at the bottom.
ESA / CNES / Arianespace / S. Martin (Guiana Space Center)

BepiColombo will bring to Mercury a first-class science that will answer both old and new questions. It includes two scientific spaceships. One, the Mercury Planetary Orbiter (MPO), was built by ESA and will operate in near circular orbit near the planet. The other, Mercury Magnetospheric Orbiter (MMO), was built by JAXA and will fly into a much more elliptical orbit, far from the planet. They will always be in the same plane of orbit, which will facilitate the simultaneous observation of the behavior of the magnetic field and particles in different places near Mercury.

BepiColombo's scientific package summarizes Messenger, but with a sharper and wider vision and the benefit of two spacecraft. Both probes carry magnetometers to study how Mercury's internally generated magnetic field reacts to the vibrations of the active sun. Both carry instruments to study the exosphere of the planet – the neutral atoms and the ions were projected on the surface of Mercury by the incoming radiations. MMO also has a dust counter, which Messenger did not have.

DFO has cameras and spectrometers to take pictures and measure the composition of the surface. From its almost circular orbit, DFO will get much closer to the surface of Mercury and get much sharper images than Messenger, putting its observations in the advantage of the Messenger card. DFO will try to understand the composition of Mercury's crust and the nature of its volcanic activity and will look for evidence of when it will shrink along near-surface faults. Messenger alluded to small-scale errors that a contraction could be causing today; DFO will try to determine if the innermost planet is still active. Scientists are particularly interested in seeing Mercury's South Pole closely and for the first time, to see if it has ice reservoirs and materials rich in organic matter, such as the North Pole.

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A long way to go

This graphic was created for Planetary Society member magazine, The planetary report, and is reproduced here with permission.

It is not easy to get to Mercury. A spacecraft must lose a tremendous amount of angular momentum to approach the Sun and settle into orbit around the small planet. BepiColombo will be driven by a third spacecraft built by the ESA, the Mercury Transfer Module (MTM). MTM will use solar-electric propulsion, its huge solar panels feeding ionic thrusters that will run continuously for most of the journey. Shortly before arriving at Mercury, BepiColombo will drop the MTM, thus avoiding the need to slow down in Mercury's orbit with all that extra mass.

BepiColombo still has a long way to go, but he has accomplished the most dangerous part of his mission: the launch. The Mercury Orbit insertion in December 2025 should be a child's game in comparison. When the spacecraft completes its sixth flyby of Mercury in January of that year, it will travel slowly enough to be captured naturally, by its own gravity, the seventh time the planet and the spacecraft meet.

Until then, enjoy this replay of the launch (which begins after 38 minutes)!