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Radiation and the International Space Station: Recommendations to Reduce Risk
6.2NASA PROGRAMS THAT INVOLVE RADIATION
The Space Radiation Health Program (Code U) conducts ground-based radiation studies with appropriate particle species and energy ranges to simulate space radiation effects on cell depletion, on tissue and bone, and on health and living matter in general. These ground-based studies are being carried out at Brookhaven National Laboratory with the expectation that a recent restructuring of the budget will allow the research to be funded and developed in accordance with program objectives. Ground-based research is less expensive than research in space and allows more elaborate and varied experiments to be conducted and repeated. At present, however, not all aspects of the space radiation environment can be simulated in ground-based experiments, especially the synergistic effects of multiple, simultaneous forms of radiation. Thus, ground-based radiation studies must be complemented at least occasionally by well-chosen experiments in space.
The SEE program (Code M), based at MSFC, has close ties to technology and engineering interests at NASA headquarters. SEE is a wide-ranging program: it comprises a number of working groups, and there is participation from other NASA centers, including the Goddard Space Flight Center (GSFC), the Jet Propulsion Laboratory (JPL), and Lewis. Its goal is "to collect, develop, and disseminate the space environment technologies that are required to design, manufacture and operate reliable, cost effective spacecraft for the government and commercial sectors that accommodate or mitigate the effects of the space environment." Towards fulfilling this goal, it provides engineering definitions of the space environment, databases, and design guidelines and attempts to update its capabilities through directed research in response to an occasional NASA Research Announcement (NRA). The SEE program has fostered the development of models of the space radiation environment through its technical working groups, NRAs, and workshops. SEE products, including models and databases, are made freely available to "current and future government and commercial space missions."
One recent SEE study, the Orbiting Technology Testbed Initiative (OTTI) Integrated Trade Study, involved many participants from MSFC and other NASA centers and the DOD and a few participants from the private sector. The objective of the program was to determine the need for and the feasibility of developing a means to test instruments and components for spacecraft that will operate in the high-radiation environment of middle to high altitudes in geospace (above low Earth orbit). Shielding, communications, computer dependability, and the overall reliability and durability of space operations were of central concern to OTTI. The final study recommended that a testbed program be developed utilizing a secondary payload platform to keep costs down. Test flights could begin in a year or two and would be modest in size, mass, and cost, with shared input and objectives from the government and private sectors. Because of its engineering and technology outlook, OTTI did not place scientific needs and requirements among its top objectives, although it did identify science needs. The "trade study" aspect of OTTI refers to the sharing of costs and resources among NASA, DOD, and the private sector.
In October 1998, NASA headquarters adopted a Strategic Program Plan for Space Radiation Health Research (Code U) and designated the Johnson Space Center as the lead center to manage and implement it. The program's goal is to achieve the exploration of space by human beings without subjecting them to unacceptable risks from exposure to ionizing radiation. Implementing the program entails integrating basic science and engineering tools to predict and manage radiation risk for ISS and other deep space exploration projects.
Also located at JSC, the Space Radiation Analysis Group (SRAG) is part of the EVA support team. As was described in Section 1.5, SRAG's responsibilities are to give the flight surgeon the information needed to help protect astronauts from excessive radiation exposure during spaceflight. EVAs are of special concern since an astronaut is shielded less against radiation inside a space suit than inside a spacecraft. SRAG provides preflight projections of the crew's exposure to radiation, real-time estimates of their exposure during flight, and postflight analysis of the radiation actually experienced. For EVAs, a radiation hazard assessment is made in real time, from one hour before EVA egress to its conclusion. SRAG makes go/no go and start/stop recommendations to the flight surgeon, who reports to the flight director.
The radiation program within the Office of Space Science (Code S) concentrates on two themes: the Sun-Earth Connection and Solar System Exploration. Through the years, Code S has accomplished most of the basic research leading to our current knowledge of the space radiation environments of Earth, other planets, and interplanetary space. Of the missions now operating, the most relevant are those in the Mars program and the