People have known about the existence of Mercury since the BCE period. However, due to the difficulty of placing a spacecraft into orbit around Mercury, and the intensely hot environment created by the strong sunlight that is ten times as strong as it is on Earth, only two missions (Mariner10 and Messenger) have been sent to Mercury so far.
BepiColombo, an international mission to study Mercury, is the first large-scale cooperative project between Japan and Europe that will make comprehensive and multifaceted observations of the magnetic field, magnetosphere, internal structure, and surface of Mercury for the first time. The mission comprises of two orbiters, the JAXA Mio (MMO: Mercury Magnetospheric Orbiter) and the ESA MPO (Mercury Planetary Orbiter), which are travelling in a combined configuration towards Mercury.
Mercury and Earth are the only planets with their own magnetic fields among the terrestrial planets that also include Mars and Venus. In comparing these two planets, it may be possible to obtain clues to understanding Earth’s magnetic field and magnetosphere as well as the various magnetospheres which exist in space.
Mercury also has a unique structure not seen in other planets, which includes an enormous core that is three quarters of the planet radius. By studying the surface and the inner structure of the planet in detail, it may be possible to further understand the process of planet formation, such as how planets in the area closest to the Sun were created.
Mio (MMO) was launched on October 20, 2018, combined with MPO developed by Europe. It is scheduled to arrive at Mercury in November 2026 after approximately 8 years. After arrival, Mio will be separated, extend its antenna and mast, and then begin science observations.
| Name | MIO (MMO:Mercury Magnetospheric Orbiter) |
|---|---|
| International Designation code | 2005-031B |
| Objectives | The BepiColombo project is a large-scale mission to perform a comprehensive study on Mercury including its magnetic field, magnetosphere, interior and surface with two Mercury Planetary Orbiter (MPO) explorers developed by ESA and Mercury Magnetospheric Orbiter MIO developed by JAXA. Missions of MIO ・Elucidation of its intrinsic magnetic field ・To discover the cause of formation of the planet's magnetic field by measuring magnetic field around Mercury with high accuracy. ・Elucidation of unique magnetosphere different from the earth's ・To identify universality and specificity of the planet magnetosphere in comparison with the earth's by observing structure and movement of the magnetosphere. ・Elucidation of thin atmosphere released from Mercury's surface ・To observe large-scale structure and variation of thin atmosphere mainly consisting of natrium, and to discover the process of generation and disappearance. ・Observation of interplanetary space near the Sun ・To observe strong shock waves near the Sun that are not seen around the earth, and to reveal their energy process. |
| Launch Date | 10:45:28 a.m., October 20, 2018 (JST) |
| Launch Location | Guiana Space Center, Kourou, French Guiana |
| Launch Vehicle | Ariane 5 rocket |
| Weight | Total weight: approx. 250 kg, observation instruments: approx. 40 kg |
| Shape | Octagonal cylinder, 180cm long from face to face and 90cm high Equipped with four wire antennas (15m) for electric-field and radio-wave measurement and two masts (5m) for magnetic-field measurement |
| Orbital Altitude | Perihermion 400 km, Apohermion 12,000 km |
| Orbital Inclinarion | 90° |
| Type of Orbit | Orbit around Mercury |
| Orbital Period | Approx.9.3 hr |
| Scientific Instruments(Planned) | 1.MGF (Magnetic Field Investigation) studies magnetic field from the planet, magnetosphere, and interplanetary solar wind. 2.MPPE (Mercury Plasma Particle Experiment) studies plasma & neutral particles from the planet, magnetosphere, and interplanetary solar wind. 3.PWI ( Plasma Wave Investigation) studies electric field, electromagnetic waves, and radio waves from magnetosphere and solar wind. 4.MSASI (Mercury Sodium Atmosphere Spectral Imager) studies thin sodium atmosphere of Mercury. 5.MDM (Mercury Dust Monitor) studies dust from the planet and interplanetary & interstellar space. |
| Pamphlet | ・Mission to Mercury BepiColombo (MIO -Mercury Magnetospheric Orbiter- ) |
