Formally, the Americans were the first to bring dosimeters to the moon as part of the Apollo missions. But they did not share the measurement data with the rest of the world, so it is officially believed that the level of radiation on the natural satellite of the Earth was first measured by the Chinese Chang’e-4 apparatus in January 2019. According to a publication in the journal Science Advances, it was 1,369 microsieverts per day.
Direct recalculation, taking into account hours and days, shows that the natural level of radiation on the Moon is about 200 times higher than the accepted safe norm for the Earth of 0.5 microsievert per hour. This exceeds the psychological mark of 1 millisievert per day, which means that in a thousand days a person will receive more than 1 sievert of radiation, and this is a guaranteed radiation sickness and death from its consequences. Fortunately, space missions are much shorter today.
However, already in 2024, an American astronaut, certainly a female, should land on the moon as part of the Artemis program. She will not be alone, the whole team will spend at least a week there, and the list of tasks includes several distant transitions. This will be a real test for the anti-radiation protection system that NASA will provide astronauts, because Chang’e-4 found out that the moon has its own source of radiation. This is the result of the interaction of cosmic radiation with regolith, in addition to the solar wind, galactic cosmic rays, etc.
A probable mission to Mars poses even more problems, because there a person is guaranteed to spend more than a year in space. And even if he can then go back, it will double the amount of radiation received. Even with the best prognosis, a deeply ill person with acute radiation sickness will return back. Therefore, the development of effective means of anti-radiation protection is task number 1 for future space flights.