JAXA’s Mercury Magnetospheric Orbiter (also known as Mio) is a spin-stabilised spacecraft that will make 15 rotations per minute, with its spin axis 90º to the Sun. It will operate from a 9.3 hour elliptical polar orbit, that will take it between 590 and 11 640 km above the planet’s surface.
Because it won’t be spinning during the journey, Mio will be protected by the Magnetospheric Orbiter Sunshield and Interface Structure (MOSIF). This ESA-built component will not only provide thermal protection but also mechanical and electrical interfaces for Mio, before it is discarded after arriving at Mercury.
The MMO has five science instruments:
Mercury Magnetometer (MMO-MAG): Providing a detailed description of Mercury’s magnetosphere and of its interaction with the planetary magnetic field and the solar wind. Principal Investigator: Wolfgang Baumjohann, Austrian Space Science, Graz, Austria.
Mercury Plasma Particle Experiment (MPPE): Seven sensors studying plasma and energetic particles in the magnetosphere and the interaction between the solar wind and Mercury’s magnetosphere. Principal Investigator: Yoshifumi Saito, Institute of Space and Astronautical Science, Kanagawa, Japan.
Mercury Plasma Wave Instrument (PWI): In situ and remote-sensing analysis of electric fields, plasma waves and radio waves in Mercury’s plasma environment. Principal Investigator: Yasumasa Kasaba, Tohoku University, Sendai, Japan.
Mercury Sodium Atmosphere Spectral Imager (MSASI): Measuring the abundance, distribution and dynamics of sodium in Mercury’s exosphere to investigate its sources and related processes. Principal Investigator: Ichiro Yoshikawa, University of Tokyo, Japan.
Mercury Dust Monitor (MDM): Studying the distribution of interplanetary dust in the orbit of Mercury. Principal Investigator: Masanori Kobayashi, Chiba Institute of Technology, Japan.