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Highlights: [•] ISSCREM is able to predict measured TEPC dose equivalent values at the Zvezda Service Module panel 327 (SM-327). [•] Measured dose equivalent from GCR and trapped radiation sources are predicted to within 10% and 20%, respectively. [•] Trapped radiation dose equivalent is dependent on TEPC location and orientation but GCR component varies minimally. [ABSTRACT FROM AUTHOR]

Abstract: A rapid analytical procedure for the prediction of a micro-dosimeter response function in low Earth orbit (LEO), correlated with the Space Transportation System (STS, shuttle) Tissue Equivalent Proportional Counter (TEPC) measurements is presented. The analytical model takes into consideration the energy loss straggling and chord length distribution of the detector, and is capable of predicting energy deposition fluctuations in a cylindrical micro-volume of arbitrary aspect ratio (height/diameter) by incoming ions through both direct and indirect (δ ray) events. At any designated (ray traced) target point within the vehicle, the model accepts the differential flux spectrum of Galactic Cosmic Rays (GCRs) and/or trapped protons at LEO as input. On a desktop PC, the response function of TEPC for each ion in the GCR/trapped field is computed at the average rate of 30s/ion. The ionizing radiation environment at LEO is represented by O’Neill’s GCR model (2004), covering charged particles in the 1⩽ Z ⩽28 range. O’Neill’s free space GCR model is coupled with the Langley Research Center (LaRC) angular dependent geomagnetic cutoff model to compute the transmission coefficient in LEO. The trapped proton environment is represented by a LaRC developed time dependent procedure which couples the AP8MIN/AP8MAX, Deep River Neutron Monitor (DRNM) and F10.7 solar radio frequency measurements. The albedo neutron environment is represented by the extrapolation of the Atmospheric Ionizing Radiation (AIR) measurements. The charged particle transport calculations correlated with STS 51 and 114 flights are accomplished by using the most recent version (2005) of the LaRC deterministic High charge (Z) and Energy TRaNsport (HZETRN) code. We present the correlations between the TEPC model predictions (response function) and TEPC measured differential/integral spectra in the lineal energy (y) domain for both GCR and trapped protons, with the conclusion that the model correctly accounts for the increase in flux at low y values where energetic ions are the primary contributor. We further discuss that, even with the incorporation of angular dependency in the cutoffs, comparison of the GCR differential/integral flux between STS 51 and 114 TEPC measured data and current calculations indicates that there still exists an underestimation by the simulations at low to mid range y values. This underestimation is partly related the exclusion of the secondary pion particle production from the current version of HZETRN. [Copyright &y& Elsevier]

Abstract: The radiation impact to astronauts depends strongly on the particles’ linear energy transfer (LET) and is dominated by high LET radiation. It is important to investigate the LET spectrum for the radiation field in low Earth orbit (LEO) and the influence of radiation on astronauts. The best active dosimeter used for all LET is the tissue equivalent proportional counter (TEPC); the best passive dosimeter used for high LET is CR-39 plastic nuclear track dosimeters (PNTDs). TEPC and CR-39 PNTDs were used to investigate the radiation in LEO. LET spectra and radiation quantities were obtained for STS-112 and STS-114 missions with TEPC and CR-39 PNTDs. This paper introduces the operation principles for the two types of dosimeters, presents radiation results measured and compares the results obtained with different dosimeters. [Copyright &y& Elsevier]

Abstract: The Sun goes through cycles of high and low activity that repeats approximately every 11 years. The solar activity is correlated to the number of dark spots on the Sun which are sources of sudden, sporadic eruptions, releasing energetic particles into space. This can directly affect the ionosphere and radio communications around the Earth. A spectacular and unusually high sunspot activity occurred during October and November 2003, commonly referred to as the Halloween Storms. The increased radiation exposure at aircraft altitudes during such an event is of major concern to international aviation organizations, airlines, governmental authorities and aircraft crew as well as flight passengers. Here, we report radiation exposure measurements made by ARC Seibersdorf research (ARCS) onboard commercial aircraft using a tissue equivalent proportional counter (TEPC). A unique set of long-term measurements was collected before, during and after the storm at flight altitudes. The results of these investigations give an understanding of the combined effects of magnetic field disturbances and solar particle fluence due to a solar storm, showing a 70% variation in the radiation exposure at typical flight altitudes. Whilst several predictive codes exist the radiation exposure to aircrew during a solar storm is difficult to predict by calculation models. These calculation models are still struggling with the high uncertainty of spectral input data provided by satellites during a solar storm. A reliable dose assessment concept to assess the radiation exposure to aircrew caused by a solar storm using a network of dosimeter instruments on-board several aircraft can be achieved. Such a proposal has been already introduced by experts of the European Radiation Dosimetry Group (EURADOS). [Copyright &y& Elsevier]