Whitepaper #080 in the Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033. Main topics: basic research. Additional topics: other basic research; space-based missions/projects; user-need-driven basic space weather research.
The particle and radiation environment in cis-lunar space is becoming more important as space exploration efforts turn to the Moon and beyond. This paper highlights gaps in energetic particle measurements. We recommend key observations near Earth and distributed measurements in the heliosphere, magnetosphere, and lunar surface to improve the scientific understanding of these particle populations.