Simulations of MATROSHKA experiment outside the ISS using PHITS

The radiation environment at the altitude of the International Space Station (ISS) is substantially different than anything typically encountered on Earth in both the character of the radiation field and the significantly higher dose rates. Concerns about the biological effects on humans of this highly complex natural radiation field are increasing due to higher amount of astronauts performing long-duration missions onboard the ISS and especially if looking into planned future manned missions to Mars. In order to begin the process of predicting the dose levels seen by the organs of an astronaut, being the prerequisite for radiation risk calculations, it is necessary to understand the character of the radiation environment both in- and outside of the ISS as well as the relevant contributions from the radiation field to the organ doses.