DORELI: A COLLABORATIVE APPROACH TO RADIATION MEASUREMENTS IN A SPACE HABITAT

Kurzfassung

The radiation environment in the International Space Station (ISS) is among the most complex encountered by humans. Measuring it, together with its orbital variations and the effects of internal shielding, is essential for a detailed assessment of the radiation risks for human health and to strengthen the countermeasures aimed at mitigating these risks. Simultaneous measurements using a set of detectors enable cross-calibration and cross-verification, leading to more refined results and a more comprehensive characterization of the radiation environment. This approach also provides data to reduce the dependence of the measurements on detector-specific characteristics. In 2020, we initiated a collaboration to compare measurements from four radiation detector systems co-located in the ISS Columbus laboratory: LIDAL (URTV, ASI), REM(JSC/SRAG-NASA), and the DOSIS 3D DOSTEL-1 and DOSTEL-2 units (DLR, CAU). All instruments employ silicon sensors but differ in hardware design and sensor characteristics. LIDAL is a large 49 cm long telescope consisting of 18 striped silicon planes and two segmented scintillator planes (8 × 16 cm²). REM is a compact hybrid silicon pixel detector (Timepix) with a 256 × 256 pixel matrix at a 55 m pitch, providing a sensitive area of 1.982 cm². The DOSTEL instruments are silicon telescopes composed of two round Canberra PIPS detectors (6.93 cm²) separated by 15 mm. In this talk, however, the DOSTEL data are taken from a single detector operated as a dosimeter. The two DOSTEL units are installed inside the DOSIS-MAIN-BOX beneath the EPM rack in the Columbus module with fixed viewing directions along the ISS X and Y axes. LIDAL is periodically rotated along the ISS X, Y, and Z axes, and the REM detector, mounted on the LIDAL lid within the LIDAL field of view, follows all LIDAL rotations. The combined measurement period now exceeds six years (shorter for REM, which joined later), allowing the study of a substantial portion of the solar cycle, from solar minimum to beyond the recent solar maximum. Differences among the measurements primarily arise from variations in field of view, energy acceptance, local shielding, and hardware strategies. Overall, the results show strong agreement. The combined dataset is used to enhance the analysis of each detector, to extract synergistic results not achievable with individual instruments alone and to strengthen the statistical significance of the findings. Fluxes and doses measured over complete ISS orbits, including passages through the South Atlantic Anomaly (SAA), will be presented and discussed. The DORELI data are available through the RadLab database within the Open Science Data Repository at NASA Ames Research Center.