Experimental lithium fluoride crystals flown aboard NASA’s Orion spacecraft during the uncrewed Artemis I lunar mission have recorded cosmic radiation doses near the Moon. Researchers report that while total radiation levels are higher than those in Earth orbit, the difference is smaller than expected.
More than 10,000 small radiation detectors were embedded inside two human-shaped models, known as phantoms, aboard the Orion capsule during the late November and early December 2022 lunar flyby of the uncrewed Artemis I mission.
Among them were several dozen experimental fluorescent lithium fluoride detectors. They were developed at the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow. Around 600 other detectors were supplied by the Polish institute.
The research formed part of the international Matroshka AstroRad Radiation Experiment (MARE).
Tracking Cosmic Particles With Lithium Fluoride Crystals
The Polish lithium fluoride crystals require no cumbersome chemical processing, unlike conventional passive track detectors made of plastic that require chemical treatment before readout. Scientists can observe particle tracks directly using a standard fluorescence microscope, according to researchers at IFJ PAN.
The affected areas emit red fluorescent light when the crystals are illuminated with blue light in a laboratory. The crystals were developed over the past decade.
Better track resolution than conventional plastic detectors is achieved by this measurement approach, which allows researchers to register a broad range of particle types and energies.
Professor Paweł Bilski noted that the detectors recorded many particle tracks that deposited less energy than the lower detection threshold of existing detectors
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Results obtained using the lithium fluoride crystals differed by no more than 15 percent from measurements gathered using conventional track detectors across the entire overlapping range of energy deposition values.
Comparing Radiation Near the Moon to Low Earth Orbit
Data analyzed from the MARE experiment reveals that total radiation doses near the Moon are higher than those experienced by astronauts in low Earth orbit. However, the increase is not as dramatic as scientists initially anticipated.
Our measurements show that, because of the large amounts of galactic radiation, total doses near the Moon are indeed higher than in Earth orbit, but not nearly as much as one might intuitively expect.
Prof. Paweł Bilski, co-author of the study
Particles can pass directly through the human body while depositing only a fraction of their energy along the way because galactic radiation possesses extremely high energy.
Consequently, the radiation dose distribution recorded inside the mannequins during the Artemis I mission was essentially uniform. This contrasted with the nonuniform distribution caused by low-energy protons stopping at varying depths inside phantoms in low Earth orbit.
Funding and Publication Details
The Polish contribution to the experiment was funded through a grant from the National Science Centre.
Findings from the analysis of the data collected during the Orion spacecraft’s journey around the Moon were published in the journal Radiation Measurements.