Space Radiation Hazards and the Vision for Space Exploration: A Report on the October 2005 Wintergreen Conference

Naturally occurring radiation to which astronauts may be exposed come in three main forms: galactcosmic rays (GCRs), charged particles accelerated to high energies by eruptive events at the Sun (solar energetic particles, or SEPs), and highly energetic particles trapped in the inner magnetospheres of the Earth and other magnetized planets. Figure 1 shows the various types of radiation that pervade our solar system (heliosphere). Humans traveling outside the confines of Earth’s atmosphere are subjected to GCRs, SEPs, and trapped magnetospheric particles. All three forms of radiation can present serious health risks to astronauts (Table 1) and can adversely affect the technological systems on which both astronaut safety and mission success depend. Protecting astronauts from space radiation has been of intense concern to NASA since the beginning of the human space program. In particular, NASA’s Vision for Space Exploration (VSE) calls for a human mission to the Moon by 2020 and eventually for expeditions to Mars. The implementation of the VSE program, which will take astronauts beyond the relative safety of low-Earth orbit, has given efforts to understand and manage the space radiation threat a challenging new context and urgency. To explore the implications of this new context for the solar and space physics community, NASA, the National Science Foundation, and the National Research Council