Biological Effects of Space Radiation

The radiation exposure in space missions can be reduced by appropriate measures, but it cannot be prevented. The reason is that space radiations due to their high energy deeply penetrates in matter. In comparison to the shielding thickness of the atmosphere of approximately 10 meter water equivalent, a spacecraft provides only 1-30 cm shielding depending on the equipment installed inside the spacecraft. Much more shielding cannot be provided due to mass constraints. A small shelter may be constructed, but the shielding thickness is still far away from that what the atmosphere provides. In the orbit of the International Space Station (ISS) the radiation exposure due to galactic cosmic radiation and the radiation belts results for long term missions in an considerable access risk for cancer mortality. In extravehicular activities (EVAs) due to solar particle events exposures may occur resulting in acute radiation effects. Since risks from this exposures cannot be eliminated, they are treated as occupational hazard. Highest possible accuracy on information is therefore essential concerning the radiation environment and their biological effects for the evaluation of the radiobiological risk.