"The European Space Agency’s project MATROSHKA (MTR), dedicated to determine the radiation load on astronauts in- and outside the International Space Station (ISS), launched in Jan. 2004 and is currently in its experimental phase 3. MTR is an anthropomorphic upper torso phantom containing over 6,000 radiation detectors to determine the depth- and organ dose distribution in the body. It is the largest international research initiative performed in the field of space dosimetry, combining the expertise of leading research institutions all over the world. Consequently it generates a huge pool of data of immense value. Aiming at optimal scientific exploitation, the project HAMLET will bring together a European expert committee, consisting exclusively of members of the MTR consortium, to process and compile the data acquired individually. Based on experimental input as well as on radiation transport calculations, a three-dimensional model for the dose distribution in an astronaut’s body will be built up. The results describe the exposure conditions both for extra-vehicular activities (MTR-1:2004–05) and inside the ISS (MTR-2A/B:2006–08). The project goes beyond essential data analysis and incorporates a modelling approach to guide new experimental measurements and strengthen the predictive capacity. This allows further utilization of the data, particularly with respect to detailed modelling of radiation interactions in the human body. The scientific achievements contribute essentially to radiation risk estimations for future interplanetary human missions, putting them on a solid experimental and theoretical basis. The synthesis of data, considerably extending previous knowledge, constitutes a major accomplishment by which Europe can establish worldwide leadership in this special branch of space radiation research. Public outreach is assured by making the data and reports available to the scientific community and the public via a web-based database and a dedicated homepage."