Radiation protection guidelines for space activities

At the beginning of the space age the dangers of hurtling into space were considerable. Despite this fact, radiation risks were examined in the U.S.S.R. and the U.S.A. and recommendations were made to limit the exposure of the crews to radiation. To date the radiation exposures of crews on missions in low-Earth orbits have been low. Now that missions in low-Earth orbit are becoming longer in duration and new missions into deep space are being considered, radiation protection guidelines become more important. Recently the estimates of the risks of radiation-induced cancer have been increased and new guidelines on radiation exposure limits for crew members must be developed. For deep space missions the guidelines take into account the risks posed by heavy ions. Unfortunately, knowledge about these risks is insufficient. If the new risk estimates are applied, current career dose limits may have to be reduced by a factor of two.