Euro-Japanese mission to study the smallest planet in the solar system

The Euro-Japanese planetary mission BepiColombo took off from the European Spaceport in French Guiana at 3:45 am, summer time from Central Europe, on October 20, 2018 (at 19:45 local time), at Edge of an Ariane 5 launcher. "Not only is the mission to investigate the planet Mercury, but it will also bring new information about the solar system," says board member Walther Pelzer Director of the Space Administration of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt); DLR). "Once again, in meeting this huge challenge, Japan is proving to be a reliable aerospace partner for Europe." The cosmic journey of the spacecraft through the internal solar system will last about seven years.

Two ships will study mercury together

BepiColombo is the most comprehensive European project to date for exploring a planet in the solar system. The mission consists of two orbiters that will circle Mercury – Mercury Global Mercury Orbit (DFO) and Mercury Magnetospheric Orbit (MMO). While DFO is designed to study the surface and composition of the planet, the MMO will analyze its magnetosphere. Other objectives of the mission include the study of the solar wind, the internal structure, and the global environment of Mercury, as well as its interaction with the Sun's closest environment. Scientists hope that this will also provide new information on the formation of the solar system.

During the trip, the two orbiters will travel aboard the Mercury Composite Spacecraft (MCS), which will supply them with energy and, thanks to a special shield – the MOS Sunshield and Interface Structure (MOSIF) – will protect them from variable extreme temperatures between 430 degrees Celsius on the day side and minus 180 degrees Celsius on the night side.

MERTIS and BELA – Using sensors in extreme conditions

Three of the 16 instruments aboard the satellite were developed mainly in Germany: BELA (BepiColombo laser altimeter), MPO-MAG (MPO magnetometer) and MERTIS (mercury radiometer and thermal infrared spectrometer). MERTIS is an infrared imaging spectrometer and radiometer equipped with two radiation sensors that will operate in the wavelength range of 7 to 40 micrometers. Once in orbit, MERTIS will study the surface and interior of Mercury aboard DFO. With a spatial resolution of 500 meters, it will identify the minerals forming rocks at the surface in the middle infrared.

Knowledge of the mineralogical composition allows scientists to make statements about the evolution of the planet. In addition, an integrated micro-radiometer will provide data on the surface temperature and thermal conductivity of mercury. Thanks to an innovative instrument concept, MERTIS is extremely compact and energy efficient. "The two MERTIS sensors are unique," says Jörn Helbert, head of DLR experiments, and adds: "The imaging channel uses an uncooled microbolometer – the first to be qualified for space in Europe – using a sensor measuring only three by one millimeter, made from a single piece of silicon and also serving as a slot for the spectrometer – these are just two of the many innovative technologies developed specifically for this experiment. The team is led by scientists from the University of Münster and the DLR Planetary Research Institute. The experiment is managed by the Institute of Optical Sensor Systems DLR, which designed and developed MERTIS. The operation is carried out under the direction of the DLR Institute of Planetary Research, while the scientific evaluation of the data is carried out with the University of Münster.

The BELA laser altimeter provides information on the global shape, rotation and topography of the planet closest to the sun. Every second, it sends 10 laser pulses to Mercury and receives the signal reflected by the surface in a fraction of a second. The higher the point of the landscape, the shorter the time required by the laser pulse to get to the surface and from there to the BELA sensor. From the duration of millions of laser pulses, a 3D model of the entire Mercury surface will emerge during the mission. "In addition, we can use the shape of the reflected pulses to determine the roughness of the surface, which helps us better understand the physical and geological processes that shape the planet," says Hauke ​​Hußmann, BELA's scientific project manager. . Sophisticated protective measures and complete protection of heat and light prevent the instrument from overheating or damaging the radiation due to the extreme temperatures of the planet. BELA was developed and built by DLR in collaboration with the University of Bern, the Max Planck Institute for Solar System Research, the Instituto de Astrofísica de Andalucía and the industry. The operation and scientific evaluation of the data is done under the direction of the DLR Planetary Research Institute.

The MPO-MAG experiment is a high resolution digital magnetometer. As already discovered by the Mariner 10 probe, Mercury is surrounded by a magnetic field whose intensity corresponds to 1% of the Earth's magnetic field. In MPO-MAG, two sensors are used on one of DFO's arms to study Mercury's magnetic field. One of the objectives is also the exploration of the internal structure of Mercury. Karl-Heinz Glaßmeier of the Institute of Geophysics and Extraterrestrial Physics (IGEP) of the Technical University of Braunschweig is scientifically responsible.

The long journey in space

It will take about seven years for BepiColombo to reach Mercury. During this time, the spacecraft will perform several tilting maneuvers in front of Earth and Venus and even six to Mercury itself before being directed to its final orbital trajectory on the destination planet. During these tilting maneuvers, the probe uses the gravitational force of the celestial bodies to gain momentum to continue its journey in space or, also, to slow down. For an orbit to be realized, the probe must not only significantly reduce its speed to Mercury, but also counteract the gravitational gravitational pull of the Sun. MERTIS will already take measurements during Earth and Venus changes. Once at Mercury, BepiColombo will collect data for about a year.

Mercury – Our "Unknown" Neighbor of the Solar System

Mercury is more than the smallest planet. With a diameter of 4878 kilometers, it is barely larger than the moon. It is also the least explored planet of the solar system in our solar system. This is primarily due to the fact that it is the Sun's closest neighbor, emitting radiation six times more intense than the Earth, which causes a temperature of up to 430 ° C during the day, before the temperature rises. cool. at minus 180 degrees Celsius at night. In the past, only two spacecraft had visited Mercury: NASA's Mariner 10 had flown over Mercury three times, in 1974 and 1975, while NASA MESSENGER's probe had flown over three flights and bypassed our neighbor as she approached her. Northern hemisphere of our planetary neighbor. exploratory mission between 2011 and 2015. BepiColombo will perfectly complement the Messenger mission, because the southern hemisphere can also be captured accurately. At the same time, new surveys will be carried out. No MESSENGER instrument has observed the planet in the middle infrared. As a result, MERTIS will provide a new dataset.

Narrow Euro-Japanese cooperation

ESA is responsible for the mission as a whole, but also for the development and construction of the planetary mercury orbiter. The Japanese space agency JAXA has provided the magnetospheric mercury orbiter. The German part of the BepiColombo mission was coordinated and funded largely by the DLR Space Administration with the help of funds provided by the German Federal Ministry of Economy and Energy (BMWi) . The two instruments BELA and MERTIS, which have been extensively developed by the Berlin-Adlershof planetary research and optical sensor research institutes DLR, have been financed mainly by means provided by DLR Research and Technology. The mission also benefited from the support of the Max Planck Institute for Solar System Research (MPS) in Göttingen, the University of Münster and the TU Braunschweig. A European industrial consortium led by the company Airbus Defense and Space provides the industrial part of the spacecraft.

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Video: BepiColombo mission to Mercury