Brad Gersey

Global real‐time dose measurements using the Automated Radiation Measurements for Aerospace Safety (ARMAS) system

The Automated Radiation Measurements for Aerospace Safety (ARMAS) program has successfully deployed a fleet of six instruments measuring the ambient radiation environment at commercial aircraft altitudes. ARMAS transmits real-time data to the ground and provides quality, tissue-relevant ambient dose equivalent rates with 5-minute latency for dose rates on 213 flights up to 17.3 km (56,700 ft.). We show five cases from different aircraft; the source particles are dominated by Galactic Cosmic Rays but include particle fluxes for minor radiation periods and geomagnetically disturbed conditions. The measurements from 2013–2016 do not cover a period of time to quantify Galactic Cosmic Rays’ (GCRs) dependence on solar cycle variation and their effect on aviation radiation. However, we report on small radiation “clouds” in specific magnetic latitude regions and note that active geomagnetic, variable space weather conditions may sufficiently modify the magnetospheric magnetic field that can enhance the radiation environment, particularly at high altitudes and mid- to high-latitudes. When there is no significant space weather, high latitude flights produce a dose rate analogous to a chest X-ray every 12.5 hours, every 25 hours for mid-latitudes, and every 100 hours for equatorial latitudes at typical commercial flight altitudes of 37,000 ft. (~11 km). The dose rate doubles every 2 km altitude increase, suggesting a radiation event management strategy for pilots or air traffic control, i.e., where event-driven radiation regions can be identified, they can be treated like volcanic ash clouds to achieve radiation safety goals with slightly lower flight altitudes or more equatorial flight paths.

Tissue Equivalent Proportional Counter Microdosimetry Measurements Aboard High-Altitude and Commercial Aircraft

FAA = Federal Aviation Administration NASA = National Aeronautics and Space Administration TEPC = Tissue Equivalent Proportional Counter ARMAS = Automated Radiation Measurements for Aviation Safety SBIR = Small Business Innovative Research ER-2 = Earth Resource – 2, a variant of the Lockheed U-2 aircraft KC-135 = Kerosene Cargo – 135, a reduced gravity aircraft operated by NASA EMF = Electromagnetic Field

Spectral Characterization of Secondary Radiation from Regolith Materials

Numerous studies have proposed the use of regolith as potential space radiation shielding for human habitats and equipment, in its raw dirt form or manufactured composite bricks and/or tiles. We have studied the shielding effectiveness of various compositions of regolith composites using physics based modeling tools. The material is modeled in the form of slabs equivalent to standard construction bricks. The production of secondary neutrons, protons and gamma rays from the interaction of primary radiation (protons with energy range 20 MeV - 1 GeV) is characterized using MCNPX multi particle capability. Additionally, the spectral characteristic of the secondary radiation behind the composite surface is evaluated. Impacts of three different parameters are studied: the composition of the regolith composite, the thickness of the slab and the energy of the impinging radiation. The secondary radiation production rates, the percent attenuation of the incident particles and the spectral characteristic of the secondary radiation are presented in this paper. Previous studies by us and others have shown that secondary radiation, particularly neutrons and gammas, becomes acute as the thickness of the shielding increases. The spectrum characterization is essential to accurately determine the dose deposition in biological tissue and the Single-Event-Effects (SEE) in electronic systems. The results of this study are complimentary to our experimental measurements and benchmark activities. The data generated from this work will be applied to evaluate different mission scenarios for the Moon and Mars.