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Mercury, the smallest and sunniest planet, is considered a world of extreme. Its temperatures vary between the hot and the cold, between 430 degrees Celsius of the day and -180 degrees of the side of the night. Mercury is the fastest planet in the solar system and only needs 88 days for a solar orbit. The exploration of this mysterious world is laborious. In addition to differences in temperature, a spacecraft must deal with the extreme gravity of the sun and extreme exposure to radiation.
Nevertheless, the European Space Agency Esa wants to go to the heart of the mysteries of Mercury: Saturday morning, at 3:45, the probe BepiColombo Euro-Japanese part of the space station of Kourou in French Guiana to go on the planet even less known of our solar system. The journey from the probe to the interior of the solar system will take about seven years.
An error causes the mission to fail
It is only in April 2026 that research can begin. "That's Columbus in the 21st century," said Elsa Montagnon, chief of the probe's flight control team. According to Esa's information, the project is the most ambitious interplanetary mission in its history. "An error could ruin the mission," said Paolo Ferri, head of Esa's mission.
The Italian mathematician Bepi Colombo (1920-1984) had already calculated the bases of a trajectory towards Mercury. The preparations for the mission of around 1.3 billion euros lasted almost 20 years. The reason is also the inhospitable conditions near the Mercury: to allow the probe to survive, according to the terms of "hellish environment" of Esa, it was necessary to develop a number of new technologies .
Decelerate to not fall in the sun
The trip is also extremely complicated: "We need more energy than taking the plane to Pluto," said BepiColombo 's flight director and head of the Interplanetary Missions Department. Esa, Andrea Accomazzo, one of the biggest challenges. The distance from Earth to Pluto is much greater than that of Mercury. The need for energy is mainly due to the attraction of the sun.
The 6.40-meter tall, 4.1-tonne satellite approaches its destination on large elliptical orbits. It flies over planets nine times, among others, to slow down with maneuvers called "swing-by" and not to be looted by the sun. In tilting maneuvers, the probe uses the gravitational force of celestial bodies to absorb velocity during the rest of the race or to slow down. First, the Earth in 2020, then twice Venus and six times Mercury itself. "Every flyby of a planet requires two months of intense preparation time," says Accomazzo.
Two orbiters explore the planet together
When one expects the Mercury Target orbit to arrive in December 2025, the two independent scientific satellites separate from their spacecraft and explore the planet from different orbits. The Esa MPO (Mercury Planetary Orbiter) satellite, also called "Bepi", closely examines the surface of a largely unknown planet. The Japanese MMO (Mercury Magnetospheric Orbiter) satellite – or "Mio" – targets the magnetic field.
The purpose of the mission is to understand how our solar system was born and formed. For this, Mercury, so close to the sun, has a special meaning. Astronomers suspect that Mercury, like Earth, has a liquid nucleus that generates its magnetic field – but science does not know why. Fly-bys of the Mariner 10 and Messenger probes in the 1970s and 2010s Although many have provided data, but these are difficult to explain. According to Esa, this also includes surface erosion indicating that gas may have escaped. There are also traces of ice in the craters where the sun can not go.
24 engines and eleven on-board cameras
Eleven cameras and instruments specifically developed for the Mercury mission are onboard the MPO Esa satellite. Four of them concern German research institutes. For example, a thermal infrared spectrometer developed in Münster called "Mertis" is used to characterize the minerals and elements present on the mercury surface. At least a year is expected for research, but DFO could last up to four years. Then the orbiter should burn. It is said that the Japanese orbiter crushes on Mercury after about three and a half years.
The 24 BepiColombo engines are also more complex than any other Esa mission before. For the first time, four electric ionic workouts are included. They are powered by 42 square meters of solar cells. The outdoor temperature at Mercury is around 350 degrees, but panels with solar cells can only withstand 200 degrees, according to Elsa Montagnon. "They must be constantly diverted from the sun."
The first hours after departure are critical
"The first hour after the start is the most risky," says Accomazzo. Solar panels should be expanded quickly after start-up. Even within 47 hours, the Darmstadt space flight control center must react very quickly in the event of a problem. The first major obstacle is made after three days. About 80 specialists from Darmstadt are involved in the mission day and night during this period.
Then, it will be critical again in mid-December, when the ion engines will be used for the first time and they will be operational. If that does not work, the whole mission could fail, explains Accomazzo. But if he succeeds, it will be "relatively calm" in about a year and a half until BepiColombo goes on Earth.
Recently, Merkur made a speech when he was pushed in May 2016 into a so-called Merkurtransit before the sun.
By Sonja Fröhlich / RND / dpa
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