A Comparison of the Radiation Environments in Deep Space

Both humans and onboard radiosensitive systems (electronics, materials, payloads and experiments) are exposed to the deleterious effects of the harsh space radiations found in the space environment. The purpose of this paper is to present the space radiation environment extended to deep space based on environment models for the moon, Mars, Jupiter, and Saturn and compare these radiation environments with the earth's radiation environment, which is used as a comparative baseline. The space radiation environment consists of high-energy protons and electrons that are magnetically “trapped” in planetary bodies that have an intrinsic magnetic field; this is the case for earth, Jupiter, and Saturn (the moon and Mars do not have a magnetic field). For the earth this region is called the “Van Allen belts,” and models of both the trapped protons (AP-8 model) and electrons (AE-8 model) have been developed. Trapped proton and electron models have been developed for Jupiter (GIRE model) and for Saturn (SATRAD model). The space radiation environment also consists of extremely energetic stripped elemental nuclei ranging from hydrogen (proton) to uranium; this environment is called the galactic cosmic radiation (GCR) environment. In addition to trapped and GCR particles, the space environment is sometimes dominated by the emission of high-energy solar protons; these sporadic occurrences or events are called solar proton events (SPE's). Particle spectra (flux vs. energy) and depth dose data for several shielding materials are presented for the moon, Mars, Jupiter, and Saturn and are compared with the particle spectra and radiation exposures for earth orbit.