A research group consisting of domestic and foreign organizations such as the Japan Aerospace Exploration Agency (JAXA), the National Institute of Polar Research, and Waseda University will be installed on the outboard experiment platform of the Japanese Experiment Module "Kibo" on the International Space Station (ISS). Using the simultaneous observation data of the three observation devices developed by Japan for two and a half years, we succeeded in measuring the exposure dose due to the "concentrated heavy rain of electrons".
As the ISS passes through high magnetic latitudes at night, it may encounter a phenomenon in which electrons fall for several minutes (relativistic electron descent phenomenon / REP phenomenon). During the REP phenomenon, the number of radiation electrons increases hundreds to thousands of times during normal times in the area, so the effects of exposure of astronauts during EVA, especially to the eye (lens). Is a concern.
To measure the exposure dose, it is necessary to know the number of radiation electrons and their energy distribution.This time, in addition to the all-sky X-ray monitoring device (MAXI) capable of high- and low-energy electron counting and the high-energy electron / gamma-ray telescope (CALET), the space environment measurement mission device (SEDA-AP) was used. The REP event was determined by MAXI and CALET, and the energy spectrum at the time when REP was detected by SEDA-AP was observed.As a result, 2 events were found in the REP phenomenon in a period of about two and a half years.As a result of calculating the exposure dose, it was found that at the largest REP event on the ISS ship, the exposure dose can reach several times higher than the exposure dose received in one day in a quiet environment.
Although this level of exposure dose does not directly affect the health of aviators, the effect of radiation on the crystalline lens is related to both the dose rate and the cumulative dose, and the lower the exposure dose, the more desirable it is. Research activities that can predict the occurrence of REP events in advance are expected.
Paper information:[Space Weather] Radiation dose during relativistic electron precipitation events at the International Space Station
