Physical dosimetric evaluations in the Apollo 16 microbial response experiment

Nine biological species, including viruses, bacteria, fungi, and nematodes, were exposed to various combinations of space vacuum, galactic radiation, and solar UV light during the Apollo 16 space flight. No major changes in number of surviving cells occurred, permitting detailed genetic and somatic studies of returned test subjects. To enable dose-response studies, solar UV was employed as a mutagenic source with cells exposed to full sunlight or to components of the UV spectrum at peak wavelengths of 254, 280, and 300 nanometers over a range of energy levels. Proper in-flight UV irradiation monitoring required the development of a potassium ferrioxalate actinometer and an anaerobic photographic emulsion dosimeter which were tested for the first time in space. Studies of the mutagenic activity of cosmic-ray particulate radiation environment required measurement of its components with several lithium fluoride thermoluminescent dosimeters and a package of passive nuclear-track detectors capable of recording high-energy multicharge particles. These detectors included cellulose nitrate, Lexan, Ilford G5, and silver chloride crystals. The nuclear track detectors measured the incident heavy particles with the recorded spherical fluences with LET350,H2O>100 keV x micrometers-1 to be 19.3 +/- 1.8 particles cm-2. This value was found to be lower than that recorded by detectors located in the Biostack and the passive personnel dosimeters worn by the astronauts, suggesting a somewhat greater average shielding.