On the radiation environment during consecutive balloon flights over New Mexico and Antarctica

Abstract

Remarkably, we know more about the radiation environment onboard the International Space Station than we do about radiation values at altitudes between 30-40 km in the middle stratosphere. Within this work, we provide data about the radiation dose measured during two consecutive balloon flights flown within a 4-month timeframe over New Mexico and Antarctica Data were measured with the M-42 radiation detector. On each flight, the M-42 was installed as part of a larger research payload: MARSBOx (New Mexico, 23 September 2019); and E-MIST (Antarctica, 15 December 2019-12 January 2020). The temporal proximity of the flights provided similar prevailing space weather conditions and solar activity (minimal during each mission). Against that common backdrop, the main differences between flights, including mission duration and geomagnetic shielding could be readily compared. Near identical space weather conditions provided a window of opportunity for studying the influence of altitude and geomagnetic shielding on dose and fluence rate of galactic cosmic radiation under maximum intensity conditions. Herein, we report relevant count- and dose rates for the missions, alongside Geant4 Monte Carlo calculations; this included crossings of the Regener maximum during the ascent and descent flights over New Mexico and the absence of a distinct maximum in dose rates at zero geomagnetic shielding for the polar flight. While dose rates in silicon at float altitudes (≈35 km-39 km) were a maximum of 2.5 +/- 0.4 microGy/h over New Mexico, we reached values of up to 8.4 +/- 0.3 microGy/h over Antarctica, thereby approaching dose rates similar to the surface of Mars.