Darmstadt / Kourou (dpa) – The European Space Agency Esa wants to unveil the secrets of the sunniest planet Mercury: the BepiColombo spacecraft begins on October 20 from the Kourou space station in French Guiana to the smallest and least known planet of our solar system.
"This is Christopher Columbus in the 21st century," says the head of the probe's flight control team, Elsa Montagnon. "Mercury is a very mysterious planet". According to Esa's information, the project represents the most challenging interplanetary mission in its history: "One mistake could ruin the entire mission," says Esa's head of mission, Paolo Ferri.
The difficult journey of the European-Japanese probe to the target orbit of Mercury lasts seven years. It is not until April 2026 that research can begin, as stated by the scientist of the Esa project, Johannes Benkhoff.
The homonym is the Italian mathematician Bepi Colombo (1920-1984), who had already calculated the first bases for a trajectory of Mercury. Preparations for the mission of about 1.3 billion euro took almost 20 years. The reason is also the inhospitable conditions near Mercury: to allow the survival of the probe in this way in the words of the "infernal environment" of Esa, it was necessary to develop a series of new technologies.
The journey is also extremely complicated: "We need more energy than flying over Pluto," said BepiColombo's flight director and head of the ESA Department for interplanetary missions, Andrea Accomazzo, one of the biggest challenges. The distance from the Earth to Pluto is much greater than that of Mercury. The reason for the high energy needs is the attraction of the sun.
The 6.40 meter high and 4.1 ton spaceship approaches its destination in wide elliptical orbits. Fly past the planets nine times, among other things to decelerate and not fall on the sun. The first is Earth in 2020, then twice Venus and six times Mercury itself. "Any flight over a planet requires a few months of intense preparation," says Accomazzo.
When it is expected that the orbit of Mercury Target will arrive in December 2025, the two independent scientific satellites separate from their spacecraft and explore the planet from different orbits. The Esa MPO satellite (Mercury Planetary Orbiter), also known as "Bepi", closely observes the largely unknown planet's surface. The Japanese satellite MMO (Mercury Magnetospheric Orbiter) – or "Mio" – points on the magnetic field.
"We want to understand how our solar system has been formed and modeled," explains Benkhoff's overall goal. For this reason, Mercury, which is so close to the sun, has a special meaning.
"Probably, like the Earth, it has a liquid core that generates its magnetic field, but science does not know why," says Montagnon. Surveys of the US probes in the years 70 and 2010 would have brought a lot of data, but still a lot was not clear. "They have discovered things that no one can explain". In the words of Benkhoff, this also includes surface erosion which indicates that the gas may have escaped. There is also evidence of icy water in craters where the sun can not get there.
There are eleven cameras and instruments on board the Esa MPO satellite, four of which involve German research institutes. For example, a thermal infrared spectrometer developed in Münster called "Mertis" is used for the characterization of minerals and elements on the Merkur surface – and this too is new.
At least a year is foreseen for the research, but the MPO could last up to four years. So the orbiter should burn. It is said that the Japanese orbiter crashes after about 3.5 years on the Mercury.
The 24 BepiColombo engines are even more complex than any other Esa mission before. Four electric ion motors are included for the first time. They are powered by – a total of 42 square meters – solar cells. The outside temperature at Mercury is about 350 degrees, but the panels with solar cells could only withstand 200 degrees, reports Montagnon. "They must constantly be turned away from the sun."
"The first hour after departure is the most risky," says Accomazzo. Solar panels must be extended quickly after starting. Even in the next 47 hours, the Darmstadt space flight control center has to react very quickly, if something goes wrong. The first major obstacle is made after three days. Around 80 specialists in Darmstadt are involved in the mission 24 hours a day during this time.
So it will be critical again in mid-December, when the ion engines will be used for the first time. If that does not work, the whole mission may fail, says Accomazzo. But if it is successful, it will be "relatively quiet" in about a year and a half until BepiColombo passes close to the Earth.