The Miniaturized Electron Proton Telescope on board HERMES

The Lunar Gateway, part of NASA’s Artemis program, is a space station orbiting around the moon expected to launch in 2027. The Heliophysics Environmental and Radiation Measurement Experiment Suite (HERMES) is a suite of instruments placed on the outside of the Habitation and Logistics Outpost (HALO)  to study the coupled Sun-Earth system and monitor the Sun’s radiation environment and space weather.

We describe in detail the  Miniaturized Electron Proton Telescope (MERiT) on board HERMES. MERiT  measures electrons and protons in the energy range ~0.5-9.0 MeV and ~1-190 MeV in 11 and 20 differential energy channels respectively. MERiT is a solid-state detector telescope with the two sensor heads facing sunward and  anti-sunward directions. MERiT will study solar energetic particles, low energy cosmic rays and energetic electrons in the magnetospheric tail. 

The MERiT has also been proposed to the ARTEMIS Lunar Terrain Vehicle program. On the Lunar surface, MERIT will characterize charged particle effects on the regolith, probe for sub-surface hydration, explore micro magnetization and study dielectric discharge effects due to penetrating cosmic rays, and high energy solar protons.