MATROSHKA—The first ESA external payload on the International Space Station

Abstract

MATROSHKA is an experiment unit for studies of the depth dose distribution of the different components of the orbital radiation field at different sides of the organs of astronauts during an extravehicular activity (EVA). MATROSHKA consists of a contained human phantom upper torso, allowing the accommodation of dedicated radiation measurement devices. MATROSHKA is currently installed outside to the Russian Segment “ZVEZDA” of the International Space Station. It is designed as a “longduration, non-maintainable, space-exposed payload”. The objective of the MATROSHKA experiment is to determine the empirical relations between measurable absorbed doses and the tissue absorbed doses in a realistic human phantom exposed to the concrete radiation field to be monitored. The radiation field during EVA is that of the free space environment modified only by the space suit. Since EVAs are a substantial fraction of the work-schedule in the space station scenario, such measurements have highest priority, especially in view of long term spaceflight endeavours in the frame of space exploration. Once the ratios for the tissue absorbed doses and surface absorbed doses are known for a given radiation field around the human body, these values may be used in future exposures to determine the required tissue absorbed doses from measurements of surface absorbed doses. In addition, the objectives are to enlarge the still modest quantity of empirical data of the composition of the radiation field in space. This includes: the mapping of the radiation environment in space and its variation with time and orbital parameters (such as solar cycle, solar flare event, inclination and altitude) and the study of the modification of the radiation dose in space by mass shielding (e.g. attenuation, build up and/or activation). The collected data will be used to reduce the uncertainties of risk estimates for radiation-induced cancer and for the refinement of realistic shielding distributions in future spaceflights. There are other important scientific aspects especially regarding radiation health for the crew, help in mission planning and design of the ISS environmental monitoring package.