The Solar Particle Monitor (SPM) onboard MMO is a particle detector which is part of the housekeeping sensors (not the scientific instruments) of MMO. It consists of two silicon photo diodes (SPM1 and SPM2) with an effective area of 10 mm x 10 mm and a depletion layer thickness of 0.3 mm. Each sensor collects counts of incident particles with four different deposited energy channels (Lv.1, 2, 3, and 4). The silicon sensors are covered by a magnesium chassis and the SPM is located inside the MMO spacecraft. Radiation incident on the SPM has already passed through the satellite structure, the SPM chassis, and the chassis of other instruments, and hence the energy of the radiation coming from outer space is not measured as it is.

• Go Murakami (JAXA, Japan)
• Haruka Ueno (JAXA, Japan)
• Takeshi Takashima (JAXA, Japan)
• Shoya Matsuda (Kanazawa University, Japan)

• Tomoaki Hori (CHS, ISEE, Nagoya Univ., Japan)
• Shota Chiba (CHS, ISEE, Nagoya Univ., Japan)

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• A pair of two identical pariticle monitors (SPM1 and SPM2) employing a 10 mm x 10 mm x 0.3 mm solid state dector (SSD)
• The energy range: >70 keV (as deposited energy, not incident energy)

• Dec. 2024: the first release of Lv.2pre data (data ver.: r01-v01-00) to registered users.

• A set of Geant4 simulations were performed to estimate the actural incident proton energies of Lv.2 to 4 energy channels. For details, please refer to Kinoshita et al. (2025) at https://doi.org/10.1029/2024JA033147.

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the SPM page on the Mio-SC website