Relativistic electron precipitation bands in the outside radiation environment of the International space station

The Radiation risk radiometer-dosimeter (R3DR2) performed active dosimetry measurements outside the International space station (ISS) during the ESA EXPOSE-R2 missions from October 24, 2014 until January 11, 2016. The 10 s resolution flux and dose rate data were used to find, identify and classify the relativistic electron precipitation bands (PB) (Blake et al., 1996) in the outside radiation environment of the ISS. The PB were identified as rapid (10-40-s) dose rate enhancement from the normal (20-200 μGy h−1) outer radiation belt (ORB) level and similar fast return to the same low level. Only PB that have in the time profile dose rates larger than 10,000 μGy h−1, identical to flux larger than 4000 cm−2 s−1, for 10 or more seconds were selected. Sixteen PB were studied. The largest selected PB, delivered in the R3DR2 detector, which was behind 0.3 g cm−2 shielding, a dose of 464 μGy for 70 s. The later was larger than the ORB daily average dose rates for 366 days out of 442 days measurements during the analyzed period. The daily average doses inside of the ISS were measured, using the DOSTEL instrument, at an average level of 194 μGy d−1 (Reitz et al., 2005). This indicates that only for 70 s, the cosmonaut/astronaut, being on extra vehicular activity (EVA), where they are shielded only by their space suits, will accumulate the equivalent of about 2.5-days dose inside of the ISS. Only 1 PB was identified during the ESA EXPOSE-E mission on ISS in the period February 17, 2008-September 3, 2009, while in the more active geo-magnetically EXPOSE-R mission in 2010, 6 PB were registered. Although the obtained PB doses do not pose extreme risks for cosmonauts/astronauts health, being on EVA, they have to be considered as a possible extremely high dose rate source, which requires additional comprehensive investigations.