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Introduction Japanese page>>
Mercury Exploration: Scientific Objectives
Mercury has been known several thousands years ago.
However, "scorching environment" [10 times as strong sunlight as earth!] and "difficulty to make an orbiter" [A big thrust is required!] have obstructed the search for this planet for a long time.
The spacecraft which was able to approach Mercury until now is only the Mariner 10 (1974-5) about 30 years ago.

Although the Mariner 10 only passed through near Mercury 3 times, it brought about big results, such as the discovery of intrinsic magnetic field and Magnetosphere.
The revisit to this planet nearest to the sun was the target of the scientist over many years.

BepiColombo(*1), an Interdisciplinary Mission to Mercury, is the first large-sized joint space science project in Japan and Europe. This mission observes on many sides and synthetically the magnetic field, the magnetosphere, the interior, and the surface of Mercury.
The main objectives of this project are as follows:
  • The terrestrial planets with intrinsic magnetic field are only the earth and Mercury. Detailed observation of the Mercury magnetic field and a magnetosphere enables the first comparative studies with Earth and brings a big leap to these fields.
  • Planet Mercury has unique structures such as "a huge core" (3/4 of the radii. It might be related to its intrinsic magnetic field). Detailed observations of its interior and surface reveal the planet formation occurred in the area nearest to the sun.
We waited for about 30 years. We expect the big achievement affected for solar system science.

[*1 It is named by ESA from the Italian scientist Giuseppe Colombo, who proposed the Mercury encounter trajectory of Mariner 10.]
BepiColombo: Mission Baseline
European Space Agency (ESA) and Japan Aerospace Exploration Agency (JAXA) will send the two orbiters to Mercury: the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (MMO).
  • Mercury Planetary Orbiter (MPO): Developed and employed by ESA. Optimized to the surface and internal observations of Mercury. (3-axis stabilized / low-altitude polar orbit)
  • Mercury Magnetospheric Orbiter (MMO): Developed and employed by JAXA/ISAS. Optimized to the Magnetic field and Magnetosphere observations of Mercury. (spin stabilized / long-elliptical polar orbit)
JAXA is responsible for the MMO spacecraft, optimized to the observation of magnetic field and a magnetosphere, supported by strong scientific communities of this field.
ESA is responsible for the MPO spacecraft, and also the whole BepiColombo project including the launch, cruising, and the Mercury orbital insertion.

Both spacecraft are launched together on one Ariane 5 rocket, and will make the trip to Mercury as the unified module.
After Mercury orbital insertion, they will be separated and start the corporative observation activities.

Final selection of the payloads was done in Fall 2004. The several Euro-Japan joint payload teams are making design and development activities now.
Observation will be planned by "BepiColombo International Science Working Team", including not only the selected payload team members but also many scientists from scientific communities in Japan and Europe.
Japan Aerospace Exploration Agency (JAXA) Institute of Space and Astronautical Science (ISAS) European Space Agency (ESA) BepiColombo Project (ESA)
BepiColombo, a cooperative mission by Japan Aerospace Exploration Agency (JAXA) / Institute of Space and Astronautical Science (ISAS) and European Space Agency (ESA), will explore Mercury, the planet closest to the Sun. ISAS/JAXA is building one of the main spacecraft, the Mercury Magnetospheric Orbiter (MMO), and ESA will contribute the other, the Mercury Planetary Orbiter (MPO).
[Mercury exploration] JAXA >> ISAS >> [Space Plasma Group, ISAS/JAXA]
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