Updated Computational Model of Cosmic Rays Near Earth

An updated computational model of the galactic-cosmic-ray (GCR) environment in the vicinity of the Earth, Earth’s Moon, and Mars has been developed, and updated software has been developed to implement the updated model. The GCR model and software in their original forms, developed during the early 1990s, were based on balloon and satellite data from 1954 to 1992. This model accounts for solar modulation of the cosmic-ray contribution for each element from hydrogen through iron by computationally propagating the local interplanetary spectrum of each element through the heliosphere. The propagation is effected by solving the Fokker-Planck diffusion, convection, energy-loss boundary-value problem. Since August 1997, the Advanced Composition Explorer NASA satellite has provided new data on GCR energy spectra. These new data were used to update the original model and greatly improve the accuracy of prediction of interplanetary GCR. The updated software was also simplified significantly, relative to the original software. The updated model and software are expected to provide highly accurate GCR-environment data for use by interplanetary- mission planners in planning for protecting astronauts against radiation and ensuring radiation hardness of electronic equipment.

This program was written by Patrick M. O’Neill of Johnson Space Center. For further information, contact the Johnson Technology Transfer Office at (281) 483- 3809. MSC-23891

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