The neutron component of the lunar radiation environment

The upcoming Atermis missions will return crew to the Moon later this decade. The risk to crew and electronics from exposure to the lunar radiation environment is one of several environmental risks that must be understood to ensure mission success. The lunar radiation environment is different in comparison to the free space and low-Earth orbit environments in that the primary galactic cosmic rays and solar energetic particles interact in both man-made structures and the lunar surface, creating a unique mix of both primary and secondary radiation. Neutrons are a significant component of the secondary radiation field and span energies up to several GeV. Measurements have been made of neutrons both in orbit around the Moon (for example, the Lunar Reconnaissance Orbiter) and on the surface (Chang e 4), over a limited range in neutron energy. Several radiation transport model calculations have also been made to provide predictions of the neutron environment, as well. Measurement of neutron fluence and energy spectra are difficult, especially in a mixed radiation environment. Neutron dosimetry may be limited by the technological challenges that limit the dynamic range of neutron energies that can be measured. This paper will review measurements and calculations made to date, as well as provide additional calculations of the neutron albedo created under different conditions of lunar soil composition and topology, in order to investigate what may or may not be needed for neutron dosimetry on the Moon.