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In recent years, space agencies such as ESA, NASA, the Chinese space agency and even private sectors have been planning human deep space exploration programs to the Moon and Mars. This requires a very timely and thorough investigation to better understand the space weather conditions and effects for such deep space activities in order to further develop mitigation strategies against the associated radiation risks on humans in space.
Radiation damage in deep space comes mainly from two sources, Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs). As an omnipresent background, radiation induced by GCRs, which are modulated by solar activities, may increase the chance of long-term health consequences, such as onset of cancer, cardiovascular diseases, skin atrophy, eye cataract, leukemia, anemia, leucopenia and malfunctions of the central nervous system. On the other hand, intense solar energetic particles (SEPs) can be considered as mightily related to deterministic radiation effects which are of great concern for space exploration. Acute radiation syndrome (ARS) or sickness or poisoning or toxicity is induced after a whole-body exposure to high doses of radiation between at the Gy [J/kg] level. Such events, despite of being rather infrequent, could result in severe damage to humans and equipment and lead to potential failure of the entire mission and therefore should be detected and mitigated as immediately as possible.
Under different shielding environment, the intensity and composition of the GCRs/SEPs may vary due to the interactions of primary particles (of different energies and charges) with the surrounding material and the generation of secondaries. Therefore, a precise quantification of the change of particle spectra under different shielding environment (e.g., within a spacecraft in deep space or at Martian surface or even subsurface which might be used for future habitat shielding) using a synergistic combination of measurements and particle-transport models is essential for assessing and predicting the radiation environment therein as well as its changes during different solar activities.
Another major challenge in predicting the radiation risks for humans in space is the sudden and sporadic radiation induced by SEPs which can be very intense, dynamic and may vary drastically in time and location. Specifically speaking, the radiation and particle enhancement measured at (or predicted for) Earth’s vicinity may be completely different from of that detected elsewhere in the heliosphere as for a Mars mission, due to the different magnetic connection and distance of Mars (or the cruise spacecraft) from the acceleration and release region of SEPs near the Sun. We highlight the utmost importance of utilizing multi-spacecraft in-situ and remote sensing observations of the Sun and the heliosphere to better understand such dynamic events and their dynamic effects across the heliosphere in particular at locations where human explorations may take place.
