Austrian dose measurements onboard space station MIR and the International Space Station--overview and comparison.

The Atominstitute of the Austrian Universities has conducted various space research missions in the last 12 years in cooperation with the Institute for Biomedical Problems in Moscow. They dealt with the exact determination of the radiation hazards for cosmonauts and the development of precise measurement devices. Special emphasis will be laid on the last experiment on space station MIR the goal of which was the determination of the depth distribution of absorbed dose and dose equivalent in a water filled Phantom. The first results from dose measurements onboard the International Space Station (ISS) will also be discussed. The spherical Phantom with a diameter of 35 cm was developed at the Institute for Biomedical Problems and had 4 channels where dosimeters can be exposed in different depths. The exposure period covered the timeframe from May 1997 to February 1999. Thermoluminescent dosimeters (TLDs) were exposed inside the Phantom, either parallel or perpendicular to the hull of the spacecraft. For the evaluation of the linear energy transfer (LET), the high temperature ratio (HTR) method was applied. Based on this method a mean quality factor and, subsequently, the dose equivalent is calculated according to the Q(LET infinity) relationship proposed in ICRP 26. An increased contribution of neutrons could be detected inside the Phantom. However the total dose equivalent did not increase over the depth of the Phantom. As the first Austrian measurements on the ISS dosimeter packages were exposed for 248 days, starting in February 2001 at six different locations onboard the ISS. The Austrian dosimeter sets for this first exposure on the ISS contained five different kinds of passive thermoluminescent dosimeters. First results showed a position dependent absorbed dose rate at the ISS.

Dose assessment of aircrew using passive detectors.

Radiation exposure of aircrew is a serious concern which has been given special emphasis in the European Council directive 96/29/Euratom. The cosmic ray induced neutron component can contribute more than 50% to the biologically relevant dose at aviation altitudes. Various computational approaches to route dose assessment, e.g. CARI, are in use nowadays and are compared with experimental data. Measurements of aircrew exposure usually involve extensive instrumentation in order to cover the whole particle spectrum and energy range present inside aircraft. Due to their small size and easy handling, thermoluminescence dosemeters represent an appropriate alternative. Previous measurements onboard aircraft applying the high-temperature ratio method with LiF:Mg,Ti dosemeters for the determination of an 'averaged' linear energy transfer of mixed radiation fields demonstrate the ability of this method to evaluate the dose equivalent, according to the Q(LETinfinity) relationship proposed by the ICRP. Measurements with CaF2:Tm dosemeters are currently in progress and are discussed here.