Space radiation risk limits and Earth-Moon-Mars environmental models

Abstract

1] We review NASA's short-term and career radiation limits for astronauts and methods for their application to future exploration missions outside of low Earth orbit. Career limits are intended to restrict late occurring health effects and include a 3% risk of exposure-induced death from cancer and new limits for central nervous system and heart disease risks. Short-term dose limits are used to prevent in-flight radiation sickness or death through restriction of the doses to the blood forming organs and to prevent clinically significant cataracts or skin damage through lens and skin dose limits, respectively. Large uncertainties exist in estimating the health risks of space radiation, chiefly the understanding of the radiobiology of heavy ions and dose rate and dose protraction effects, and the limitations in human epidemiology data. To protect against these uncertainties NASA estimates the 95% confidence in the cancer risk projection intervals as part of astronaut flight readiness assessments and mission design. Accurate organ dose and particle spectra models are needed to ensure astronauts stay below radiation limits and to support the goal of narrowing the uncertainties in risk projections. Methodologies for evaluation of space environments, radiation quality, and organ doses to evaluate limits are discussed, and current projections for lunar and Mars missions are described.

The Martian surface radiation environment – a comparison of models and MSL/RAD measurements

“…In this paper, we therefore focus on the GCR spectra and their contribution to total radiation dose and dose equivalent. For the determination of the radiation exposure for different mission scenarios and the mitigation of the radiation risk of astronauts during such missions, numerical models are of great value as they allow, for instance, optimization of shielding conditions or selection of appropriate launching schedules (Cucinotta et al 2010(Cucinotta et al , 2011. Additionally, models are not only helpful for prospective mission analysis but are also able to extend and complement the measurements that were performed and thereby broaden our understanding of the radiation field by, for instance, extending the energy range of the particle fluxes or providing estimates of particle fluxes and dose rates for arbitrary atmospheric, or human fabricated shielding scenarios as well as for different solar modulation.…”

Near‐Real‐Time Situational Awareness of Space Radiation Hazards

“…Large SEP events on 23 January 2012, on 27 March 2012, and in the summer of 2012 contributed significantly to the hazards of the space environment over this interval. We observe that the dose rate limit of 200 centigrays for the lens dose [Cucinotta et al, 2010] is exceeded for nominal spacecraft shielding.Among the satellite measurements used by PREDICCS are data from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument on NASA's Lunar Reconnaissance Orbiter [Spence et al, 2010]. For the SEP events of 23 January (Figure 1 Figure 1.…”

“…Large SEP events on 23 January 2012, on 27 March 2012, and in the summer of 2012 contributed significantly to the hazards of the space environment over this interval. We observe that the dose rate limit of 200 centigrays for the lens dose [Cucinotta et al, 2010] is exceeded for nominal spacecraft shielding.…”

Commercial Space Tourism and Space Weather: An Update

“…Recent reports that discuss the details of space radiation exposure include National Research Council [2012], Cucinotta et al [2010Cucinotta et al [ , 2011, and Durante and Cucinotta [2011]. The key points are summarized here.…”