Ax-4 mission data provides Indian astronaut Subhanshu Shukla with new insight into the dangers of space radiation

In one of the first studies of its kind, scientists have analyzed sustained mission-level radiation levels to which astronauts were exposed on the Axiom-4 space mission, of which an Indian Air Force officer was a member, which will help in future space medicine research and exposure assessment in human spaceflight.

Radiation is one of the most important environmental biomedical risks in human spaceflight and is associated with long-term risks of cancer, heart disease, neurological disorders, and DNA damage. This makes careful radiation monitoring a critical element in astronaut health protection and mission planning.

Axiom-4 was an 18-day mission to the International Space Station (ISS) from June to July 2025 with a four-person crew. Group Captain Subhanshu Skukla was the commander of the Dragon spacecraft that transported the crew from the Kennedy Space Center in Florida to the International Space Station and back to Earth.

The study provides a high-resolution view of the radiation environment experienced by astronauts and payloads across the International Space Station’s operations and the transportation phases of the Dragon spacecraft. “The results indicate that the majority of the total absorbed dose accumulated during the habitation phase of the ISS, while the transfer phases contributed a smaller but still relevant portion of exposure, representing on average 8.5% of the total mission dose,” the researchers stated.

Conducted by scientists from the Doctoral School of Engineering Sciences and the Institute of Mathematics and Basic Sciences at the Hungarian University of Agriculture and Life, the study was published in Nature’s Scientific Reports, a peer-reviewed journal, on August 13. One of the astronauts on the mission was from Hungary.

The researchers used several specially designed instruments called RadNano-1K dosimeters and RadNanoPlus detectors deployed at multiple sites, which recorded human and environmental data continuously during the mission. “Unlike most previous active dosimetry studies of the ISS, this work provides continuous, high-resolution measurements across the entire mission profile, enabling detailed reconstructions of dose rate variability and cumulative absorbed dose,” the researchers said.

In low Earth orbit (LEO), astronauts are exposed to a complex mixture of galactic cosmic rays, trapped radiation from the Earth’s magnetosphere, and scattered solar particle events. The study noted that these radiation fields produce primary and secondary particles inside spacecraft structures, generating a heterogeneous radiation environment.

It is well established that such exposure is associated with an increased long-term risk of cancer, cardiovascular disease, degenerative tissue effects, acute radiation syndrome, and potential effects on the central nervous system. Even low-intensity cosmic rays can cause DNA damage.

“Despite the increasing frequency of private astronaut flights, relatively limited data on radiation exposure from these missions have been reported in the scientific literature. Direct measurements of astronaut radiation exposure on such missions are essential to improve risk assessment and support evaluation of emerging compact dosimetry technologies, designed for operational deployment,” the researchers said.