Mercury Plasma Particle Experiments - Mercury Ion Analyzer (MIA)

[Fig 24 from Saito et al., 2021]

Measurement Principle

Mercury Ion Analyzer (MIA), one of MPPE sensors onboard Mio, measures both the 3D distribution function of solar wind ions around Mercury and the planet’s magnetospheric ions to understand the structure and plasma dynamics of Mercury’s magnetosphere, Mercury-solar wind interaction, atmospheric abundances, structures, and generation/loss processes, and the solar wind at Mercury’s position. MIA consists of a top-hat type electrostatic analyzer with toroidal deflectors, microchannel plates (MCPs), high-voltage power supplies. The analyzer selects energies of ions from 10 eV/q up to 30 keV/q depending on the operation modes with 64 spin angle sectors.


Principal Investigator
Yoshifumi Saito (ISAS/JAXA, Japan)
Wataru Miyake (Tokai University, Japan)
Yuki Harada (Kyoto University, Japan)
Shoichiro Yokota (Osaka University, Japan)
Hamamatsu Photonics K. K. (Japan)
MEISEI Electric Co., Ltd. (Japan)
Mitsuya Co., Ltd. (Japan)
YS DESIGN Ltd. (Japan)

Instrument Specifications

Field of view 3.8 deg × 90 deg (high G-factor, solar wind)
5.1 deg × 90 deg (low G-factor, solar wind)
9.6 deg × 270 deg (high G-factor, Mercury ion)
6.4 deg × 270 deg (low G-factor, Mercury ion)
Angular resolution 5.625 deg × 5.625 deg (solar wind)
22.5 deg × 22.5 deg (Mercury ion)
Energy range 10 eV/q–30 keV/q
Energy resolution ΔE/E ∼ 8.3% (FWHM, high G-factor, solar wind)
ΔE/E ∼ 2.2% (FWHM, low G-factor, solar wind)
ΔE/E ∼ 12.7% (FWHM, high G-factor, Mercury ion)
ΔE/E ∼ 3.6% (FWHM, low G-factor, Mercury ion)
Stepping energies and cadence Full energy sweep with 32 contiguous energy channels every 64 times per 4s spin
Time resolution to obtain the full 3D velocity distribution function (32 energy steps) 4 s/3D distribution function
(128 energy steps) 16 s/3D distribution function
Geometrical factor High G-factor mode (5.625 deg:SW 22.5 deg:MI): 3.39×10−6 cm2sreV/eV (solar wind)
4.64×10−4 cm2sreV/eV (Mercury ion)
Low G-factor mode (5.625 deg:SW 22.5 deg:MI): 2.81×10−7 cm2sreV/eV (solar wind)
1.23×10−5 cm2sreV/eV (Mercury ion)
Mass 1.57 kg
Power 2.96 W
Dimensions 180 mm × 254 mm × 146 mm
Data rate 0.11 kbits/s (L-mode)
2.5 kbits/s (M-mode)
17 kbits/s (H-mode)
after factor 3 compression