Safe space mission Helga and Zohar provide important insights into space radiation

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During the Artemis I mission, researchers were able to collect detailed radiation data on the way to the Moon using two measurement phantoms. The measurement data provide important insights into radiation exposure in space and the necessary protective measures.

In space missions, astronauts are exposed to dangerous space radiation. To protect astronauts on longer missions, appropriate measures must be taken. This requires detailed measurement data on radiation exposure during spaceflight outside the Earth's magnetic field.

At the end of 2022, the two measuring mannequins Helga and Zohar were launched with the NASA spacecraft Orion as part of the Matroshka AstroRad Radiation Experiment MARE, led by the German Aerospace Center (DLR). During the Artemis I mission, they flew on a journey of over 25 days to the Moon and back. For the first time, continuous measurement data on the radiation levels between the Earth and its nearly half a million kilometers distant satellite were obtained.

Radiation detectors in the spacecraft and on measurement phantoms

The DLR, together with NASA and ESA, characterized the radiation differences within the Orion spacecraft. For the measurement data, "a very large number of radiation detectors, called dosimeters, were placed at various fixed positions within the spacecraft as well as in our two life-sized MARE measurement phantoms Helga and Zohar," says Dr. Thomas Berger, radiation physicist from the DLR Institute for Aerospace Medicine in Cologne and head of the MARE experiment.

The research team from DLR, ESA, and NASA has now published initial results. During the passage through Earth's proton belt, the so-called inner Van Allen belt, the radiation dose inside the spacecraft varied significantly depending on the location of the detector: The dose rates between the most and least protected areas inside the space capsule differed by a factor of four.

Measurement data are the basis for future missions

These enormous differences confirm the design and shielding concept of the space capsule. In the more heavily shielded area of the capsule, the Storm Shelter, the total dose affecting the crew can be limited to a maximum of 150 millisieverts during large solar particle events. At this dose, no symptoms of acute radiation sickness are expected.

The data also show that the orientation of the spacecraft during the proton belt traversal had a significant impact on the radiation levels within the capsule. "Our measurement data are a valuable information base for the design of future missions," says DLR radiation physicist Berger.

The researchers were supported by modern computer simulation. With its help, the radiation environments can be improved as the experimental measurement data largely match the predicted model calculations.

Alarm during a high-energy radiation event

NASA equipped the Orion spacecraft with its radiation measurement and warning system "Hybrid Electronic Radiation Assessor," or HERA for short. HERA consists of three radiation sensors installed in differently shielded areas of Orion. It is designed to sound an alarm when the crew should seek protection during a high-energy radiation event, such as a solar flare.

In this case, the crew would move to a better-shielded part of Orion and open the floor flaps, then install shielding material as additional protection over their heads. The ESA also provided five mobile dosimeters—the EAD-MUs (ESA Active Dosimeter - Mobile Units)—at various points in the space capsule to measure radiation.

Measurement phantoms are modeled after the female anatomy

The dosimeters distributed in the Orion capsule by ESA were designed, tested, and built by the DLR Institute of Aerospace Medicine in Cologne in collaboration with ASRO, Finland. The active DLR measuring devices M-42 and passive sensors in Helga and Zohar were developed and manufactured by the DLR Institute of Aerospace Medicine in Cologne. The two measurement phantoms in the MARE project were specifically modeled on female anatomy to study the particular stresses for women during long-term stays in space.

Dr. Thomas Berger and his team from the DLR project MARE are currently working on comparing the radiation exposure of Helga, the measurement dummy that flew without protection, and Zohar, who wore the AstroRad radiation protection vest during the lunar orbit. (heh)

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Link: Das Strahlungsexperiment MARE (external link).