The astronauts and cosmonauts working and living in a space station at altitudes of ~400 km are exposed to radiation levels far exceeding the natural radiation environment on the ground. The three main radiation components in low-Earth orbit (LEO) are galactic cosmic rays (GCR), emissions from the Sun – either solar particle events (SPE) or coronal mass ejections (CME) – and protons and electrons trapped in the Van Allen belts. In LEO, albedo neutrons and protons can also be found that are produced when GCR particles interact with the atmosphere and travel along trajectories reflecting them back into space. The contribution of these sources to the radiation load on humans onboard a space station varies greatly and depends on various parameters such as the orbital inclination and altitude, the shielding distribution of the spacecraft and the solar cycle. Contrary to the radiation environment on Earth, the main contribution to the dose arises from heavy charged particles encountered in GCR and protons emitted by the sun. Due to their high energies, these primary particles can easily penetrate a spacecraft wall, thereby creating a secondary radiation field, which includes neutrons. The radiation load on humans in space can therefore reach levels that are up to a factor of 100 times greater than those present on Earth. The high radiation load of this complex cosmic radiation field gives the space-faring nations a legal and moral obligation to monitor the radiation exposure of astronauts and cosmonauts, particularly for long duration missions. The data from active and passive radiation monitoring act as inputs for risk estimates for human cancer induction due to the high radiation levels. Since the internal organs of the human body are more sensitive to penetrating radiation than the skin, the determination of organ doses is an essential task. This evaluation is only possible by applying anthropomorphic phantoms that allow integration of radiation detectors inside a simulated human body.

The HAMLET project is funded by the European Commission under the EU’s
Seventh Framework Programme (FP7) and coordinated by the
German Aerospace Center (DLR)

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