The Lunar Ionising Radiation Environment - a benchmark model

A Geant4-based Monte Carlo application was developed to model the Galactic Cosmic Ray (GCR) induced radiation environment on the lunar surface. It was adapted from ESA’s detailed Mars Energetic Radiation Environment Model, incorporating lunar-specific geometry and regolith composition.

The simulations use the Badhwar–O’Neill 2020 model to derive the GCR spectrum, reproducing it both in spectra and in solar modulation. Simulations successfully reproduced the expected GCR spectra and solar modulation trends for 2009 (solar minimum) and 2015 (solar maximum). The resulting primary and albedo Linear Energy Transfer (LET) spectra showed good agreement with CRaTER measurements aboard the Lunar Reconnaissance Orbiter, accurately capturing the observed spectral shapes.

Comparisons with HZETRN calculations further confirmed consistent modeling of secondary particle production and transport. The simulation framework developed in this work establishes a reliable baseline for evaluating lunar radiation hazards and supports future analyses of shielding eWectiveness, habitat exposure, and astronaut dosimetry for both short and longduration missions.