Astronaut's Organ Doses Inferred from Measurements in a Human Phantom Outside the International Space Station

Abstract

Space radiation hazards are recognized as a key concern for human space flight. For long-term interplanetary missions, they constitute a potentially limiting factor since current protection limits for low-Earth orbit missions may be approached or even exceeded. In such a situation, an accurate risk assessment requires knowledge of equivalent doses in critical radiosensitive organs rather than only skin doses or ambient doses from area monitoring. To achieve this, the MATROSHKA experiment uses a human phantom torso equipped with dedicated detector systems. We measured for the first time the doses from the diverse components of ionizing space radiation at the surface and at different locations inside the phantom positioned outside the International Space Station, thereby simulating an extravehicular activity of an astronaut. The relationships between the skin and organ absorbed doses obtained in such an exposure show a steep gradient between the doses in the uppermost layer of the skin and the deep organs with a ratio close to 20. This decrease due to the body self-shielding and a concomitant increase of the radiation quality factor by 1.7 highlight the complexities of an adequate dosimetry of space radiation. The depth-dose distributions established by MATROSHKA serve as benchmarks for space radiation models and radiation transport calculations that are needed for mission planning.

DOSIS & DOSIS 3D: long-term dose monitoring onboard the Columbus Laboratory of the International Space Station (ISS)

“…The radiation environment onboard the ISS has been monitored since the beginning of the ISS era with various active and passive radiation detector systems (see reviews in : Berger 2008;Caffrey & Hamby 2011;Narici et al 2015) aiming for exact area monitoring within (Kodaira et al 2014) and outside the ISS . Furthermore; various experiments aimed at determining the effective dose equivalent using phantoms for the improvement of radiation risk estimations have been performed (see for example: Reitz et al 2009;Berger et al 2013, Puchalska et al 2014). In addition, passive radiation detector systems have been used as operational personal radiation detectors of the astro-and cosmonauts (Straube et al 2010).…”

Matroshka DOSTEL measurements onboard the International Space Station (ISS)

“…Therefore a comparison can only be made between MTR-DOSTEL and the passive detectors of the experiment. As for the MTR-2B mission phase the MTR-DOSTEL data does not cover the whole mission time The absorbed dose for the skin of the MTR phantom of 944 lGy day À1 (Reitz et al 2009) is more than two times higher than the results obtained with MTR-DOSTEL 373.7 lGy day À1 . The shielding of the MTR-DOSTEL is slightly higher in respect to the skin detectors.…”

“…The radiation measurement devices of MTR can be grouped into passive and active detectors. Descriptions and results of the passive detectors can be found in Reitz & Berger (2006); Reitz et al (2009) ;Zhou et al (2010); Berger et al (2013), and will not be further evaluated in this work. The active instrumentation of MTR consists of a Tissue Equivalent Proportional Counter (TEPC) provided by NASA, four Silicon Scintillator Devices (SSDs), and a Dosimetry Telescope (DOSTEL).…”

Space radiation research in Europe: flight experiments and ground-based studies

“…In recent years, the MATROSHKA experiment, supported by ESA and coordinated by DLR in cooperation with 20 research institutes, has provided a valuable dataset of organ doses in space which can be used to benchmark current models (Reitz et al 2009). MATROSHKA ( Fig.…”