Data collected during the Axiom-4 space mission, which included Indian astronaut Group Captain Shubhanshu Shukla, has provided a detailed picture of the radiation environment faced by astronauts during human spaceflight.
The findings, published in the peer-reviewed journal Scientific Reports on August 13, could help improve radiation risk assessment, astronaut health protection and future space medicine research.
Radiation is considered one of the major environmental hazards in human spaceflight. Prolonged exposure has been linked to an increased risk of cancer, cardiovascular and neurological disorders, tissue damage and changes to DNA, making accurate monitoring important for both mission planning and astronaut safety.
Axiom-4 was an 18-day mission to the International Space Station (ISS) carried out in June and July 2025. Shubhanshu Shukla, an Indian Air Force officer, served as the pilot of the Dragon spacecraft that transported the four-member crew from Florida to the ISS and back to Earth.
The study examined radiation exposure throughout the mission, covering both the astronauts' stay aboard the ISS and the transfer phases aboard the Dragon spacecraft.
Researchers found that most of the total absorbed radiation dose was accumulated during the ISS habitation phase. The spacecraft transfer phases accounted for an average of 8.5 per cent of the total mission dose, while still making a significant contribution to overall exposure.
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Scientists used specially designed RadNano-1K dosimeters and RadNanoPlus detectors placed at multiple locations to continuously record radiation levels and environmental data throughout the mission.
The researchers said the continuous, high-resolution measurements allowed them to reconstruct variations in radiation dose rates and calculate cumulative absorbed doses across the complete mission profile.
Astronauts in low-Earth orbit are exposed to a combination of galactic cosmic rays, radiation trapped by Earth's magnetosphere and occasional solar energetic particle events. These radiation fields can also generate secondary particles when they interact with spacecraft structures, creating a complex and uneven radiation environment.
The researchers said radiation data from private astronaut missions remains relatively limited despite the increasing frequency of such flights. Direct measurements from missions such as Axiom-4 can therefore help improve understanding of radiation exposure and strengthen risk assessments for future human spaceflight.
The findings could also support the evaluation of smaller, advanced dosimetry devices that can be deployed during operational missions.
With commercial human spaceflight expected to expand, the researchers said continuous radiation monitoring will remain important for assessing health risks and developing safer environments for astronauts on future missions.
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