Radiation in Space: Relevance and Risk for Human Missions

Radiation exposure of astronauts during long-term space missions exceeds dose limits for terrestrial occupational radiation exposure by far. In the atmosphere, exposure to cosmic radiation augments with increasing height, resulting in an additional average annual radiation dose to aircrew of 2 mSv in Germany. Leaving the atmosphere and entering space, the radiation exposure enhances further, by the lack of atmospheric and magnetic shielding and by the additional contribution from particles contained in the radiation belts. The complexity of the space radiation field poses a huge challenge for dosimetry and evaluation of its biological effects. Traversals of energetic charged particles of cosmic radiation can even be perceived as light flashes by astronauts after dark adaptation. Countless heavy ion accelerator experiments were and are performed in order to understand the effects of heavy ions at molecular, cellular, tissue, and organismal level and to develop countermeasures.