6.1 RADIATION: A CONCERN THROUGHOUT NASA
As the nation's civilian space agency, NASA carries out many activities that require managing the potentially harmful effects of radiation in space. The degree to which these effects must be mitigated is a function of such disparate factors as the potential for human exposure, spacecraft orbit, mission duration, and the sensitivity of spacecraft microelectronics to damage or upset. Consequently, an assortment of space radiation programs and initiatives are distributed throughout the NASA centers and across its enterprises. The priority assigned to these programs also varies; programs related to minimizing the radiation hazard to humans obviously have a very high priority.
While some coordination among these activities exists, CSSP/CSTR believes more would be beneficial. This is reflected in the principal recommendation of this section, which suggests a way to better coordinate NASA's many programs that involve radiation. In the context of this report, the recommendation should be viewed as one element in an integrated program to reduce radiation risk to astronauts involved in ISS construction, maintenance, and operations.
Some units at NASA headquarters and NASA centers have their own programs to cope with the effects of radiation in space, and some units participate in other NASA radiation programs. The programs, several of which are described below, vary according to the area of responsibility of the involved unit. Some relate to engineering applications, others to high-altitude aircraft flights, spacecraft and hardware design, spacecraft operations and reliability, scientific research, or humans in space. At NASA headquarters, programs involving radiation exist in the Office of Life and Microgravity Sciences and Applications (Code U), the Office of Space Flight (Code M), and the Office of Space Science (Code S). Code S, with an emphasis on science, treats space radiation as a phenomenon that it must factor into many of its scientific priorities and objectives, particularly those concerned with major solar disturbances and subsequent geomagnetic storms and disturbances. Code M, with an emphasis on engineering, supports the Space Environment Effects (SEE) program (described below) based at the Marshall Space Flight Center (MSFC). Code U, with an emphasis on biology and medicine, includes NASA's Space Radiation Health Program at headquarters. To convey a sense of the range of diversity of the programs within NASA that involve radiation, a few of the programs are briefly described here.
6.2 NASA 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
International Solar-Terrestrial Physics (ISTP) program, now in its extended phase. ISTP and complementary Sun-Earth Connection missions such as ACE, First Auroral Snapshot Explorer (FASE), and SAMPEX employ an unprecedented fleet of spacecraft to study the Sun, interplanetary space, and Earth's magnetosphere by means of simultaneous observations from different locations in the system (see Chapter 4). For the first time, events can be followed as they develop in space and time, and cause-and-effect relationships can be established. ISTP and the complementary missions were created with solid scientific objectives that continue to be valid. They also show great promise of advancing the scientific understanding of the dynamical space radiation environment of Earth and interplanetary space, which is another reason for extending them. Of particular note, the ISTP theory program has made significant advances in magnetohydrodynamic global modeling of the magnetosphere and its dynamical responses to interplanetary disturbances originating at the Sun (see Appendix A). Since these missions provide the data that relate to the radiation environment, they constitute a common resource for the space radiation activities of the NASA codes and centers. Accordingly, let us turn now to communication across codes and centers.
6.3 COMMUNICATION BETWEEN PROGRAMS WITH AN INTEREST IN RADIATION
A radiation coordinating team involving Codes U, S, R (Office of Aerospace Technology), M, and A (Office of the Administrator) has been established at headquarters to bridge interests across NASA. The team has the authority to conceive and implement projects that cut across codes and centers, but a noticeable absence of such projects suggests that it has been less active than it needs to be to achieve its potential. Instead of coming from the team, cross-code initiatives come from individual project managers. A recent example was the useful discussions and expressions of interest in cooperation between the Office of Life Science (Code U) and the Office of Space Science (Code S), particularly the latter's Sun-Earth Connection Theme and its Solar System Exploration Theme. These discussions resulted in Code U being given the opportunity to conduct Mars radiation environment studies utilizing the Mars Surveyor 2001 and 2003 missions. There are two further areas of endeavor where the coordination of radiation activities within NASA would yield benefits.
Radiation Models for NASA Operations
To satisfy the space weather and engineering requirements of the SEE program, it is necessary to construct better space environmental radiation models than now exist. New models should have a strong scientific basis with regard to both data quality and modeling techniques. A project such as this, which is described in Appendix A, belongs naturally in Code S, but its application is to activities in Code M. A mechanism for cross-code coordination would help here.
Radiation Data for NASA Operations
SRAG confronts severe limitations in trying to fulfill its responsibilities. Although information useful to SRAG may be available from currently operating NASA satellites, none of the mission objectives of these satellites address the needs of SRAG or the issue of human safety in space. It is essentially a matter of luck and not of program priority when a NASA spacecraft becomes available to SRAG. As Chapter 4 details, these spacecraft could be very helpful to SRAG as it tries to fulfill its responsibilities. In the Apollo era, the research and human spaceflight sides of NASA were more tightly coupled. In 1961, the IMP program was planned and ''sold" in direct response to the radiation hazard to astronauts in the Apollo program. After the Apollo era, however, and until recently, when the relevance of space weather was emphasized by the Sun-Earth Connection Theme in the Office of Space Science, a relatively low priority was assigned to developing a quantitative understanding of the Earth's space radiation environment. The scientific foundations of this discipline need to be strengthened to facilitate development of the quantitative physical models of disturbed conditions needed by SRAG. Also there is no program or initiative in NASA, such as the Rapid Prototyping Center (RPC) at NOAA (see Chapter 5), that promotes the transformation of physical research models of the space weather environment into operational
models such as would be needed by SRAG. The importance of developing operational models for nowcast or forecast purposes has been recognized by the National Space Weather Program (NSWP), but as yet only limited progress has been made, mainly by NOAA's RPC.
6.4 SUMMARY AND RECOMMENDATION
There are major programs at NASA that require an accurate knowledge of Earth's radiation environment. The kind of knowledge required varies from program to program, but the range of knowledge needed extends from the basic science, the physical processes, and the generation mechanisms of the radiation belts and particle events, to net integrated radiation doses averaged over a long period of time. The trend in recent years at NASA has been to smaller and cheaper spacecraft with smaller instruments, more onboard data processing, and increased use of microelectronics. For these and other reasons, the working knowledge of Earth's radiation environment (models, forecasts of particle events and disturbances, integrated doses, etc.) should be improved to address current planning and development requirements in just about every area of NASA activity. A better understanding of the radiation environment, which can come from programs within NASA, would be a great advantage to other NASA projects in science, engineering, technology, and the human spaceflight program. CSSP/CSTR believes the enormous complementary strength in personnel and resources at the different NASA centers should be utilized synergistically to support the needs of both the manned and unmanned programs for information on the space radiation environment.
Recommendation 6: To coordinate intra-NASA activities and concerns in radiation, NASA should establish an agency-level radiation plan and task force. It should also establish a multidisciplinary steering committee to advise the task force.
For greatest effect, the radiation plan should be developed under the leadership of headquarters and with approval of the NASA administrator. The envisioned task force, which could be a revitalized version of the existing radiation coordinating team, would be responsible for managing the radiation plan. CSSP/CSTR suggests that a number of elements be incorporated when implementing this recommendation. The task force would operate across codes. It would report to appropriate high-ranking officials in several offices at NASA headquarters (at the associate administrator level and appropriate program directors or managers). It would prepare an annual report and would be co-led by two or more NASA centers.
CSSP/CSTR suggests that MSFC and JSC be among the centers taking the lead. MSFC is managing the SEE program. JSC is responsible for safeguarding humans in space. CSSP/CSTR suggests that the steering committee be appointed by headquarters and that it have a rotating membership, ensuring representation from other agencies, universities, and industry. It is important that there be representatives on the task force from GSFC and JPL. GSFC representation is important because Goddard has strength in the basic science underlying space radiation, which is crucial for developing and implementing models and designs. For example, the National Space Science Data Center at Goddard could evaluate the scientific merits and inadequacies of current scientific and engineering models and databases. JPL's presence on the task force is needed because JPL is the lead center for deep space missions and so should take part in policy and program developments that involve the interplanetary environment. Also, it has played an important role in developing models of space radiation and space storms.