Scientists Share First Artemis I Radiation Measurements Results

Outer space is an environment where spacecraft and astronauts are exposed to several radioactive sources. Solar activity, galactic cosmic rays, and the charged particles that form the Van Allen belts are among them. Limiting the exposure of astronauts is an important part of mission design. During the Artemis I mission, which took place in late 2022, scientists measured and mapped radiation exposure during a lunar flight.

By using detectors placed in the spacecraft and on mannequins, future lunar missions will be better equipped to protect astronauts from dangerous levels of exposure.

The experiments

Radiation detectors were placed all over the Orion capsule and on two mannequins, named Helga and Zohar. The European Space Agency contributed five mobile dosimeters based on the already-flown EuCPAD. This acronym stands for European Crew Personal Active Dosimeter, which consists of a wearable unit for data collection and a storage device for charging and data transfer.

The dosimeter was tested by ESA Astronauts Andreas Mogensen and Thomas Pesquet on the ISS. A similar system is under development for use on the Gateway space station.

*The mannequins that flew aboard Artemis I: Zohar (left) and Helga (right). The black garment worn by Zohar is the AstroRad protective vest. Credits: DLR*

The dosimeters allowed researchers to measure radiation doses during the entire journey from the Earth to the Moon. They also allowed them to assess the effectiveness of the more shielded parts of the capsule. Moreover, one of the two mannequins was wearing an AstroRad vest, which uses high-density polyethylene to further shield the most critical parts of the body.

The results

Teams from ESA, NASA, and DLR (the German Aerospace Center) have now published their findings. The scientists found that in the most shielded parts of the spacecraft, exposure is four times lower than in the least protected areas. This result thus validates the design of the shielding.

The dose from solar particles events in these areas was found to be less than 150 millisieverts. This level of radiation exposure avoids putting the astronauts at risk of experiencing acute radiation sickness.

NASA’s Space Launch System rocket carrying the Orion spacecraft launches on the Artemis I flight test, Wednesday, Nov. 16, 2022, from Launch Complex 39B at NASA’s Kennedy Space Center in Florida. NASA’s Artemis I mission is the first integrated flight test of the agency’s deep space exploration systems: the Orion spacecraft, Space Launch System (SLS) rocket, and ground systems. SLS and Orion launched at 1:47 a.m. EST, from Launch Pad 39B at the Kennedy Space Center. Photo Credit: (NASA/Bill Ingalls) — NASA’s Space Launch System rocket carrying the Orion spacecraft launches on the Artemis I flight test, Wednesday, Nov. 16, 2022, from Launch Complex 39B at NASA’s Kennedy Space Center in Florida. Photo Credit: NASA/Bill Ingalls

The spacecraft’s attitude was also found to influence radiation exposure. During the flyby of the inner Van Allen belt, Orion rotated by 90 degrees and reduced radiation exposure by 50%. This information will be crucial for the planning of future Artemis missions. Overall, the results show that the radiation levels aboard Orion are unlikely to exceed NASA limits for astronauts.

The future

Data analysis is still incomplete, and further aspects of the radiation exposure are still under investigation. For example, scientists are continuing to compare exposure levels on mannequin Helga, who did not have a protective vest, and Zohar, who had. This insight will help to further improve crew safety on future missions.

“The Artemis I mission marks a crucial step in advancing our understanding of how space radiation impacts the safety of future crewed missions to the Moon. With radiation monitors placed throughout the Orion capsule, we are gaining valuable insights into how space radiation interacts with the spacecraft’s shielding, the types of radiation that penetrate to reach the human body, and which areas inside Orion offer the most protection.

This knowledge is invaluable, as it will allow us to accurately estimate radiation exposure for ESA astronauts before they journey into deep space, ensuring their safety on missions to the Moon and beyond.”
— Sergi Vaquer Araujo, Lead for the Space Medicine Team

This work will be crucial in the planning of crewed lunar missions. The first one will be Artemis II, scheduled for no earlier than September 2025.

^{*Cover image credits: NASA}