Models Of Ionizing Radiation In The Lunar Environment
- Paper number
IAC-07-A1.9.-A2.7.02
- Author
Dr. Giovanni De Angelis, Istituto Superiore di Sanita' (ISS), Italy
- Year
2007
- Abstract
In view of manned missions targeted to the Moon, for which radiation exposure is one of the greatest challenges to be tackled, it is of fundamental importance to have available a tool, which allows the determination of radiation fluxes and doses at any time and at any point of the lunar surface. With this goal in mind, models of radiation environment due to Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE) on the Moon have been developed, and fluxes and spectra hereby computed. The work is described as models of incoming cosmic and solar primary particles impinging on the lunar surface, transported through the subsurface layers, with backscattering taken into account, and interacting with some targets described as material layers. Time dependent models for incoming particles for both GCR and SPE are those used in previous analyses as well as in NASA radiation analysis engineering applications. The lunar surface and subsurface has been modeled as regolith and bedrock, with structure and composition taken from the results of the instruments of the Luna, Ranger, Lunar Surveyor and Apollo missions, as well as from groundbased radiophysical measurements. In order to compare results from different transport techniques, particle transport computations have been performed with both deterministic (HZETRN) and Monte Carlo (FLUKA) codes with adaptations for planetary surfaces geometry for the soil composition and structure of the Apollo 12 Oceanus Procellarum landing site, with a good agreement between the results from the two techniques. GCR-induced backscattered neutrons are present at least up to a depth of 5 m in the regolith, whereas after 80 cm depth within regolith there are no neutrons due to SPE. Moreover, fluxes, spectra, LET and doses for most kinds of particles, namely protons, neutrons, alpha particles, heavy ions, pions, muons etc., for various other lunar soil and rock compositions have been obtained with the deterministic particle transport technique. The results from this work can only be compared in literature with previous versions of the same models or with very simplistic models. This Moon Radiation Environment Model will be tested against spacecraft instruments data (e.g. RADOM onboard the CHANDRAYAAN-1 spacecraft from Indian Space Research Organization ISRO) in the near future.
- Abstract document