National Space Development Agency of Japan Space Experiments Group
Waseda University
Waseda University
Nihon University
Nihon University
Institute of Physical and Chemical Research
Tokyo University of Fisheries
National Cancer Research Center
Nara Medical University
PL Botanical Institute
出版者
宇宙開発事業団
出版者（英）
National Space Development Agency of Japan (NASDA)
This experiment aims to measure cosmic radiation, especially Highly EnergiZed Electrons (HZE) that easily reaches the inside of a space ship by penetrating the outer wall, and secondary radiation generated from the synergetic effects between HZE and the ship body and payloads, using track detecting materials and a thermoluminescence dosimeter. This experiment also aims to investigate and evaluate the effects of the cosmic radiation on organisms at different levels such as cellular or individual level. The equipment used consists of two sets of cosmic radiation monitoring containers and 13 sets of dosimeters. The former was filled with piled stacks in which organic samples were sandwiched between solid state track-detecting materials called 'Hurtlus'. The latter includes the Hurtlus and ThermoLuminescence Dosimeters (TLD). The organic samples used include corn and soybean seeds that are sensitive to radiation, dried Artemia salina eggs, and 14 bacteria such as Escherichia coli mutants without DNA repair ability. These detecting devices and organic samples were returned to Japan for physical dose analysis and biological experiments about two weeks after the experiments in the Endeavor were over. Measuring doses with lithium fluoride TLD resulted in large dispersion with low reliability. However, measuring doses with magnesium silicate TLD showed good results with little dispersion in spite of low dose. Distribution of HZE's Liner Energy Transfer (LET) derived from solid track-detecting material analysis showed good qualitative agreement with the results of the same orbital experiments, such as IML-1 or D-1. However, the ratio of absorbed dose rate to dose equivalent rate, which was inferred from the results of the TLD and solid state track-detecting materials, was lower than that measured in the Johnson Space Center of NASA. The two kinds of plant seeds did not show any statistically significant change in somatic cell mutation: the soy bean seeds were confirmed to be more sensitive to radiation than corn seeds. Etch pit analysis of the track-detecting materials sandwiching the Artemia salina eggs allowed us to choose the eggs exposed to heavy ion beams. The exposed eggs showed that the picnosis frequency of juvenile cells was significantly higher than the ground samples. The tetracycline-resistant rate of dried Bacillus subtilis spores bearing plasmid DNA pHY300PLK was about 90 percent in the ground samples, while that of the flight samples was about 70 percent. This decrease suggests damages on the plasmid DNA or damaged host genes. The change in the survival rate of the 11 Escherichia coli mutants without enzyme activities involved in DNA repair was comparatively analyzed after returning to the Earth.
宇宙放射線の生物影響の検討と宇宙飛行士の放射線防御対策の開発
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