Space radiation dosimetry onboard Mir and ISS. Overview and comparison

The radiation environment in space consists mainly of protons, electrons and heavy charged particles (HCPs) and interacts with the hull of a spacecraft, thereby producing a complex secondary radiation field that additionally includes neutrons, photons, muons and pions. The major issue of our studies concerns the development of highly precise instrumentation to provide a basis for a reliable estimation of hazardous radiation effects in astro- and cosmonauts. The paper gives an overview of the related missions with emphasis laid on the phantom experiment onboard Mir station and the first Austrian dose measurements onboard the International Space Station (ISS). Radiation doses were determined by means of thermoluminescent dosemeters (TLDs) of different types which have been calibrated individually prior to and after the flights. By application of different TLD types, information on the neutron dose can be achieved. The dose rates onboard the ISS are generally lower, although the orbital parameters are almost identical. This is partially addressed to the different solar activity conditions. The Phantom-1/2 experiments were performed in the time-frame from May 1997 to August 1998, whereas BRADOS-1 was conducted February to November 2001. On the other hand, the absorbed dose rates depend on the different shielding properties of the spacecraft. The difference between the TLD-600 and TLD-700 TL signals confirms that the neutron contribution onboard Mir is enhanced