Radiation research without frontiers - from ISS to Mars

Paper number

IAC-06-A1.7.-A2.7.02

Author

Dr. Guenther Reitz, German Aerospace Center (DLR), Germany

Year

2006

Abstract

Risk from exposure to ionizing radiation is determined from the level of the exposure in the different organs taking into account the radiobiological quality of the radiation field and the radiosensitivity of the organs. Accurate measurements of the radiation exposure are one of the prerequisites for precise risk estimation. 
One attempt to provide accurate measurements is the determination of the depth dose distribution inside a human phantom using the ESA-Facility MATROSHKA. The facility houses a phantom upper torso consisting of 33 slices composed of natural bones which are embedded in tissue equivalent plastic. The Phantom slices are equipped with channels and cut-outs to allow the accommodation of active and passive dosemeters, temperature- and pressure sensors. The radiation experiments accommodated in the facility are performed under leadership of DLR in a cooperation of more than 15 research institutes from Europe, Japan and the US. The so-called MATROSHKA experiment represents therefore the currently biggest international radiation experiment ever performed in space. Seven active and over 6000 passive detectors constitute the radiation experiments which are not located only inside the phantom but also on top of the head of the phantom, in front of the belly and around the body as part of a Poncho and a Hood. The instrument suite is build up by thermoluminescence detectors, plastic nuclear track etch detectors with and without converter foils, a silicon detector telescope, plastic scintillators and a tissue equivalent proportional counter.
The MATROSHKA experiments allow the determination of the empirical relations between measurable absorbed doses at the skin and the tissue absorbed doses in different depth inside the phantom. Once the ratios for the tissue- and surface absorbed doses are known for a given radiation field around the human body, these values may be used in future exposures during long haul space flights e.g. a flight to Mars to determine the required tissue absorbed doses from measurements of surface absorbed doses, only. MATROSHKA measurements will therefore serve as benchmark for model calculations. 
For manned explorative missions the radiation exposure can be only approximate determined by model calculations which need to be validated by measurements in precursor missions. In the frame of the European ExoMars mission a lightweight particle spectrometer combining various techniques of radiation detection in space is in development.  Its design from heritage components makes it a powerful experiment to deliver at minimum risk outstanding scientific data. It shall characterize for the first time the radiation environment on the cruise to Mars and on the Mars surface, and provide dose and dose equivalent rates as precursor information absolutely necessary to develop ways to mitigate the radiation risks for future human exploration on Mars. The data are deemed necessary for the validation of atmospheric radiation transmission models and radiation transport codes. 

Abstract document

IAC-06-A1.7.-A2.7.02.pdf

Manuscript document

IAC-06-A1.7.-A2.7.02.pdf (🔒 authorized access only).

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