DOSE ASSESSMENT WITH PASSIVE DETECTORS INSIDE THE COLUMBUS LABORATORY ONBOARD THE INTERNATIONAL SPACE STATION ISS

Abstract

The natural human exploratory urge is driving humankind to discover the universe and plan future human space missions to distant objects. Regarding the radiation exposures during exploration of space, the radiation environment, which significantly differs from the radiation environment on Earth, is one of the main hazards in space. The Van-Allen radiation belts, the Galactic Cosmic Rays and the Solar Particle Events significantly contribute to the increased radiation exposure in space compared to Earth. It is therefore important to determine the radiation field in respect of solar activity, orbit parameters and different shielding conditions. The “DOSe distribution inside the ISS” (DOSIS) experiment, under the lead of the German Aerospace Center (DLR) is an approach to measure the spatial and temporal radiation distribution inside the Columbus laboratory on-board the International Space Station (ISS). Remarkable about the DOSIS experiment is the enabling of a comparison of data measured by different institutions with different measurement methods and materials. For the first time twelve institutes compared radiation measurement results for a defined experiment condition. Active and passive dosimeters distributed at eleven positions inside the Columbus laboratory measured the radiation field and the radiation distribution inside Columbus for two different periods in the years 2009 and 2010. The two “DOSimetric TELescopes” (DOSTEL) belong to the active dosimeters. Thermoluminescence detectors (TLD) and “plastic nuclear track etch” detectors (CR-39) were used as passive dosimeters, to determine a complete coverage of the entire Liner Energy Transfer (LET) range. The comparison of DLR data, as well as the comparison with data provided by other participating groups for both experiment periods consistently showed good agreements. A decrease of daily absorbed dose rates from experiment phase I to II due to the increasing solar activity was observed. A spatial dose distribution inside the Columbus module based on different shielding conditions could be seen as well. The lowest daily absorbed dose rates were observed at the “European Drawer Rack” (EDR), while the daily absorbed dose rates increased up to 36%, which were measured at the “Human Research Facility 2” (HRF-2). These results can be used for further benchmarking and development of radiation transport codes and a better risk estimation in order to enable long duration space mission.