Space Radiation Hazards and the Vision for Space Exploration Report of a Workshop (2006) / Chapter Skim
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3 Operational Strategies for Space Weather Support
3 Operational Strategies for Space Weather Support
Pages 38-53
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CURRENT OPERATIONS SUPPORT (SPACE SHUTTLE AND INTERNATIONAL SPACE STATION MISSIONS IN LOW EARTH ORBIT) The Space Radiation Analysis Group (SRAG)
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The impact of GCR is also lower during solar maximum, because the increased speed and density of the solar wind intensifies the interplanetary magnetic field generated by the Sun, making it more difficult for GCR to penetrate the inner solar system. Radiological Support During Missions The radiation consoles in the Mission Control Center at Johnson Space Center (JSC)
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Radiation Monitoring Instruments and Dosimeters The present suite of detectors used to monitor the radiation environment during manned missions includes passive dosimeters (crew passive dosimeter [CPD] and radiation area monitor [RAM]
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Twenty-four hours of ISS ground track overlaid with the magnetic shielding boundaries for quiet and active storm conditions and the South Atlantic Anomaly. The quasi-latitudinal pair of high-latitude lines in each hemisphere indicates the low-latitude borders of areas accessible to radiation from solar energetic particle (SEP)
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· GCR and SEP event environmentDetermine the limits of the long-term variability in the space radiation environment, including GCR and SEP events, through continued research into the long-term
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Solar monitoring is required in order to place the forecasts and observations of SEP events into a context of ongoing and potential solar activity. Near-real-time observations of solar active regions and emerging coronal mass ejections (CMEs)
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The generic elements of a radiation risk mitigation strategy include space environment situational awareness, radiation exposure forecasting, and exposure impact and risk analysis. These elements combine to generate recommendations to the mission commander to keep the radiation exposure as low as reasonably achievable.
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Risk management architectures are likely to take advantage of a space weather network designed to protect Earth, with additional elements added to measure or estimate astronaut exposure and to provide communication links to the Moon base and astronauts on surface EVA. Space Space Environment Environment Radiation Safety Observations Models Information Flow Dosimetry, Radiation Space Transport Environment Models Situational Awareness Mission Manifest, Flight Rules, Other Safety Exposure Factors Forecast Data Archive Exposure Impact and Verification, Risk Validation Analysis Crew Recommendations Exposure to Mission History Commander FIGURE 3.3 Components of the radiation safety information flow leading to specific recommendations to the mission commander.
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The final determination of the appropriate elements of the risk mitigation architecture will depend on many things. On the forecast side, the most significant consideration will be the state of the art in predicting the eruption and character of coronal mass ejections and the evolution of associated SEP events.
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It is reasonable to assume that an Earth-based solar-monitoring network (including orbital elements such as geosynchronous particle detectors, the planned NOAA soft x-ray imager, and research-quality solar monitors as employed on the Solar and Heliospheric Observatory and planned for future NASA solar missions) will be available to support SEP event monitoring, alerts, and forecasts.
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Shielding Dose/Dose-Rate Monitors Spacecraft Communications Particle Environment Monitor(s) Habitat Rover Suit Dosimeter Data Concept of Surface Operations Outlook/ Warning/ Impact/ Instructions Alert Options to Astronauts Space Weather SRAG and Flight Mission Forecast Center Surgeon Operations Climatology Limits Flight Plan Nowcast Environment Models and Flight Rules Forecast Analysis Input Transport Code FIGURE 3.5 One potential construct of a space radiation warning architecture.
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Since the spacecraft will be the only source of shelter on a Mars mission for the hundreds of days that the crew will be in deep space, it is critical that it provide adequate shielding to protect the crew from the steady GCR exposure and the sudden impact of multiple large SEP events. NASA has known for some time that shielding on the order of 100 to 200 g/cm2 or more would be necessary to reduce dose equivalent in space to Earth background levels (Nealy et al., 1989; Simonsen et al., 1990)
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However, since this limited approach is similar to what is done today, significant advances in the understanding of SEP events will be necessary to improve on the currently available false-alarm rate, miss rate, and poor flux estimation capability.
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Despite Mars's lack of a significant magnetic field, the thin atmosphere (2 percent of the thickness of Earth's atmosphere) , and the planet's mass, which reduces particle fluxes by one-half, will provide additional shielding to protect astronauts on the martian surface from GCR and SEP event radiation.
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Supplemental data could be obtained relatively inexpensively by placing energetic particle detectors and plasma monitors on interplanetary targets of opportunity during the years preceding the Mars mission. A distribution of in situ data points could provide valuable information on the state of the interplanetary magnetic field, solar wind conditions, and propagation conditions for shocks and SEP events.
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Discussions at the workshop considered ideas for narrowing the gap so that knowledge from the solar and space physics scientists could be transferred to support the VSE. It was recognized that communication at workshops such as these, among an interdisciplinary group of participants, can identify where scientists can contribute to the high-priority needs of the users -- whether it be those versed in radiation climatology talking to mission planners and hardware engineers, or space environment modelers talking to mission operations personnel.
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