Operational astronaut and payload radiation exposure during the Axiom-4 spaceflight measured by RadNano Infinity Astronaut Dosimeters

Abstract

Abstract Accurate characterisation of the radiation environment is essential for assessing astronaut exposure and supporting space biomedical research during human spaceflights. Here we present distributed radiation measurements obtained during the Axiom-4 mission using ten compact RadNano Infinity dosimeters deployed across multiple locations. Unlike most previous ISS active dosimetry studies, this work provides continuous, high-temporal-resolution measurements across the complete mission profile, enabling detailed reconstruction of dose-rate variability and cumulative absorbed dose. Approximately 91.5% of the total absorbed dose was accumulated on the ISS, while the transfer phases contributed an average of 8.5% of the mission dose, despite their short duration. Spatial variability within the ISS was clearly observed, with module-dependent dose differences of approximately 23–28%. The South Atlantic Anomaly contributed an average of 44% of the total absorbed dose and was the dominant source of short-term dose rate peaks. Comparison with ISS reference systems showed strong agreement in temporal behaviour and, for the co-located validation unit, consistent absolute scaling. Literature-based weighting indicated estimated mission dose equivalents of about 13.7–15.6 mSv. These findings highlight the potential of compact, low-power, distributed dosimetry systems for continuous operational radiation monitoring, supporting improved exposure assessment in human spaceflight, future space medicine and dosimetry applications.