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Space Studies Board: Annual Report 2009 5 Summaries of Major Reports This chapter reprints the summaries of reports that were released in 2009 (note that the official publication date may be 2010). One report was released in 2008 but published in 2009—Launching Science: Science Opportunities Provided by NASA’s Constellation System was reprinted in Space Studies Board Annual Report—2008.
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Space Studies Board: Annual Report 2009 5.1 America’s Future in Space: Aligning the Civil Space Program with National Needs A Report of the Ad Hoc Committee on the Rationale and Goals of the U.S. Civil Space Program Summary From its inception in 1958, much of the U.S. space program was driven by opportunities to serve national interests in a geopolitical environment heavily colored by Cold War threats and fears. Originally, the true potential of space activities was largely speculative. In the ensuing decades, however, early expectations for discovery and technological accomplishment have been richly exceeded. Without a doubt, the first 50 years of the space age have been transformative. Astronauts have stood on Earth’s moon while millions watched. Commercial communications and remote sensing satellites have become part of the basic infrastructure of the world. Satellites support worldwide communications, providing a critical backbone for commerce—carrying billions of global financial transactions daily, for example. Direct broadcasting beams television signals into homes globally, delivering images that bring unprecedented awareness of events occurring throughout the world. Military global positioning satellites provide ubiquitous signals that support a stunning variety of services, from assisting in the navigation of civilian airplanes, shipping, and automobiles to transmitting timing signals that enable cell phone and power grid switching. Remote sensing satellites obtain high-resolution images of Earth’s surface, available now on the Internet for people worldwide to view and use, and provide critical information to monitor changes in our climate and their effects. Our understanding of every aspect of the cosmos has been profoundly altered, and in the view of many, we stand once again at the brink of a new era. Space observations have mapped the remnant radiation from the Big Bang that began our universe. We have discovered that the expansion of the universe continues to accelerate, driven by a force that we do not yet understand, and that there are large amounts of matter in the universe that we cannot yet observe. We have seen galaxies forming at the beginning of the universe and stars forming in our own galaxy. We have explored the wonders that abound in our solar system and have found locations where life might have occurred or might even now be present. We have discovered planets around other stars, so many that it is ever more likely that there are other Earths comparable to our own. What will the next 50 years bring? Today we live in a globalized world of societies and nations characterized by intertwined economies, trade commitments, and international security agreements. Mutual dependencies are much more pervasive and important than ever before. Many of the pressing problems that now require our best efforts to understand and resolve—from terrorism to climate change to demand for energy—are also global in nature and must be addressed through mutual worldwide action. In the judgment of the Committee on the Rationale and Goals of the U.S. Civil Space Program, the ability to operate from, through, and in space will be a key component of potential solutions to 21st-century challenges. As it has before, with the necessary alignment to achieve clearly articulated national priorities, the U.S. civil space1 program can serve the nation effectively in this new and demanding environment. In its initial discussions, the committee concluded that debates about the direction of the civil space program have too often focused on addressing near-term problems and issues without first putting those issues in the context of how a disciplined space program can serve larger national imperatives. In the committee’s view, characterizing the top-level goals of the civil space program and the connection between those goals and broad national priorities is necessary as a foundation on which the nation (both now and in the future) can devise sustainable solutions to nearer-term issues. Therefore, the committee focused on the long-term, strategic value of the U.S. civil space program, and its report does not address nearer-term issues that affect the conduct of U.S. space activities other than to provide a context in which more tactical decisions might be made. NOTE: “Summary” reprinted from America’s Future in Space: Aligning the Civil Space Program with National Needs, The National Academies Press, Washington, D.C., 2009, pp. 1-8. 1 The committee considered “civil space” to include all government, commercial, academic, and private space activities not directly intended for military or intelligence use.
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Space Studies Board: Annual Report 2009 The national priorities that informed the committee’s thinking include ensuring national security, providing clean and affordable energy, protecting the environment now and for future generations, educating an engaged citizenry and a capable workforce for the 21st century, sustaining global economic competitiveness, and working internationally to build a safer, more sustainable world. A common element across all these urgent priorities is the significant part that research and development can play in solving problems and advancing the national enterprise in each area. Instruments in space have documented an accelerating decline in arctic sea ice; mapped the circulation of the world’s oceans; enabled the creation of quantitative three-dimensional data sets to improve the quality of hurricane forecasting; and created new tools to address a host of agricultural, coastal, and urban resource management problems, to cite only a few examples. Such capabilities demonstrate what can be achieved when technologically challenging space problems stimulate innovation that leads to long-term advances with applications beyond the space sector. Civil space activities are central to the R&D enterprise of the nation, often in a transformational way, and thus present powerful opportunities to help address major national objectives. Observations from space offering unique capabilities for global environmental and land-use monitoring are essential to informed decision making about energy production and climate change policies, and they help provide the understanding required for wise management. The high visibility of space activities attracts students’ attention to science, technology, and mathematics, and space activities are an exciting focus for teaching those subjects. Commercial space-related ventures now figure significantly in global economic competitiveness, and, while government investments to stimulate the nation’s fragile economy will have short-term impacts, R&D investments can be counted on to make longer-term sustainable contributions to the nation’s economic strength. As has countless times proved the case, research in and from space will continue to lead to important future, and not always currently predictable, benefits that hold the promise of progress toward realizing U.S. as well as shared international goals. The committee’s overall conclusion is that a preeminent U.S. civil space program with strengths and capabilities aligned for tackling widely acknowledged national challenges—environmental, economic, and strategic—is a national imperative today, and will continue to grow in importance in the future. GOALS FOR THE CIVIL SPACE PROGRAM Structured and supported to match multiple responsibilities in serving key national objectives, the U.S. civil space program should be preeminent in the sense that it can influence, by example, nations’ use of space. To be a strategic leader in a globalized world requires that the United States have a civil space program whose breadth, competence, and level of accomplishment ensure that U.S. leadership is demonstrated, accepted, and welcomed. The committee identified six strategic goals that it regards as basic for guiding program choices and resources planning for U.S. civil space activities. The goals all serve the national interest, and steady progress in achieving each of them is necessary. To reestablish leadership for the protection of Earth and its inhabitants through the use of space research and technology. The key global perspective enabled by space observations is critical to monitoring climate change and testing climate models, managing Earth resources, and mitigating risks associated with natural phenomena such as severe weather and asteroids. To sustain U.S. leadership in science by seeking knowledge of the universe and searching for life beyond Earth. Space offers a multitude of critical opportunities, unavailable in Earth-based laboratories, to extend our knowledge of the local and distant universe and to search for life beyond Earth. To expand the frontiers of human activities in space. Human spaceflight continues to challenge technology, utilize unique human capabilities, bring global prestige, and excite the public’s imagination. Space provides almost limitless opportunities for extending the human experience to new frontiers. To provide technological, economic, and societal benefits that contribute solutions to the nation’s most pressing problems. Space activities provide economic opportunities, stimulate innovation, and support services that improve the quality of life. U.S. economic competitiveness is directly affected by our ability to perform in this sector and the many sectors enabled and supported by space activities. To inspire current and future generations. U.S. civil space activities, built on a legacy of spectacular achievements, should continue to inspire the public and also serve to attract future generations of scientists and engineers.
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Space Studies Board: Annual Report 2009 To enhance U.S. global strategic leadership through leadership in civil space activities. Because of the growing strategic importance of space, all nations that aspire to global political and economic leadership in the 21st century are increasing their space-faring capabilities. Continued U.S. global leadership is tied to continued U.S. leadership in space. FOUNDATIONAL ELEMENTS To contribute to realizing critical national objectives, including those just listed, the U.S. space program, both the civil and the national security components, must have a strong foundation and adequate resources. While the breadth of the civil space program has grown, there is also a sense that the program has been unfocused, with corresponding impacts on the organizations and institutions that support it. The United States can no longer pursue space activities on the assumption of its unchallengeable dominance—as evidenced by the view of other nations that the United States is not the only, or in some cases even the best, option for space partnerships. U.S. leadership in space activities and their capacity to serve urgent national needs must be based on preeminent technical capabilities; ingenuity, entrepreneurialism, and a willingness to take risks; and recognition of mutual interdependencies. The time has come to reassess, and, in some cases, reinvent the institutions, workforce, infrastructure, and technology base for U.S. space activities. The committee identified four foundational elements critical to a purposeful, effective, strategic U.S. space program, without which U.S. space efforts will lack robustness, realism, sustainability, and affordability. Coordinated national strategies—implementing national space policy coherently across all civilian agencies in support of national needs and priorities and aligning attention to shared interests of civil and national security space activities; A competent technical workforce—sufficient in size, talent, and experience to address difficult and pressing challenges; An effectively sized and structured infrastructure—realizing synergy from the public and private sectors and from international partnerships; and A priority investment in technology and innovation—strengthening and sustaining the U.S. capacity to meet national needs through transformational advances. Efforts to establish each of these elements to ensure a strong foundation for the nation’s civil space program must overcome several impediments. The issues include a loss of focus on national imperatives, overly constrained resources, inadequate coordination across the federal government, missed opportunities to transition roles from government-led to private-sector-provided services, obstacles to international cooperation, weakened institutional partnerships, and lack of emphasis on advanced technology development programs. Awareness of such issues—and not an effort to resolve specific instances—guided the committee in its development of recommendations to NASA, NOAA, and the federal government at the highest levels. RECOMMENDATIONS The committee found that, in spite of their promise and utility, components of the civil space program are not always aligned to fully capitalize on opportunities to serve the larger national interest. Decisions about civil space priorities, strategies, and programs, and the resources to achieve them, are not always made with a conscious view toward their linkages to broader national interests. Accordingly, the committee recommends as follows: Addressing national imperatives. Emphasis should be placed on aligning space program capabilities with current high-priority national imperatives, including those where space is not traditionally considered. The U.S. civil space program has long demonstrated a capacity to effectively serve U.S. national interests. Recommendation 1 provides a broad policy basis on which the committee’s subsequent specific recommendations rest. The recommendations that follow address a set of actions, all of which are necessary to strengthen the U.S. civil space program and reinforce or enhance the contributions of civil space activities to broader national objectives.
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Space Studies Board: Annual Report 2009 Climate and environmental monitoring. NASA and NOAA should lead the formation of an international satellite-observing architecture capable of monitoring global climate change and its consequences and support the research needed to interpret and understand the data in time for meaningful policy decisions by Reversing the deterioration of the U.S. Earth observation infrastructure; Developing and implementing a plan for achieving and sustaining global Earth observations; Working with the international community to develop an integrated database for sensor information from all Earth-monitoring satellites; Aggressively pursuing technology development for future high-priority Earth observation missions; and Actively planning for transitions to continue demonstrably useful research observations on a sustained, or operational, basis. Scientific inquiry. NASA, in cooperation with other agencies and international partners, should continue to lead a program of scientific exploration and discovery that Seizes opportunities to advance understanding of Earth, the objects of the solar system, including the Sun, and the vast universe beyond; Includes searches for evidence of life beyond Earth; Contributes to understanding how the universe works, who we are, where we came from, and what is the destiny of our star—the Sun—our solar system, and the universe, and of the physical laws that govern them; and Is guided by peer review, advisory committees, and the priorities articulated by the science communities in their strategic planning reports, such as the NRC’s decadal surveys.2 Advanced space technology. NASA should revitalize its advanced technology development program by establishing a Defense Advanced Research Projects Agency (DARPA)-like organization within NASA as a priority mission area to support preeminent civil, national security (if dual-use), and commercial space programs. The resulting program should Be organizationally independent of major development programs; Serve all civil space customers, including the commercial sector; Conduct an extensive assessment of the current state and potential of civil space technology; and Conduct cutting-edge fundamental research in support of the nation’s space technology base. International cooperation. The government, under White House leadership, should pursue international cooperation in space proactively as a means to advance U.S. strategic leadership and meet national and mutual international goals by Expanding international partnerships in studies of global change; Leading an effort in which the United States and other major space-faring nations cooperate to develop rules for a robust space operating regime that ensures that space becomes a more productive global commons for science, commerce, and other activities; Rationalizing export controls so as to ensure ongoing prevention of inappropriate transfer of sensitive technologies to adversaries while eliminating barriers to international cooperation and commerce that do not contribute effectively to national security; Expanding international partnerships in the use of the International Space Station (ISS); Continuing international cooperation in scientific research and human space exploration; Engaging the nations of the developing world in educating and training their citizens to take advantage of space technology for sustainable development; and Supporting the interchange of international scholars and students. 2 The NRC decadal surveys have been widely used by the scientific community and by program decision makers because they (a) present explicit, consensus priorities for the most important, potentially revolutionary science that should be undertaken within the span of a decade; (b) develop priorities for future investments in research facilities, space missions, and/or supporting programs; (c) rank competing opportunities and ideas and clearly indicate which ones are of higher or lower priority in terms of the timing, risk, and cost of their implementation; and (d) make the difficult adverse decisions about other meritorious ideas that cannot be accommodated within realistically available resources.
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Space Studies Board: Annual Report 2009 Human spaceflight. NASA should be on the leading edge of actively pursuing human spaceflight, to extend the human experience into new frontiers, challenge technology, bring global prestige, and excite the public’s imagination. These goals should be accomplished by Setting challenging objectives that advance the frontier, scientific and technological understanding, and the state of the art; Establishing clear goals for each step in a sequence of human spaceflight missions beyond low Earth orbit that will develop techniques and hardware that can be used in a next step further outward; Focusing use of the ISS on advancing capabilities for human space exploration; Using human spaceflight to enhance the U.S. soft power leadership by inviting emerging economic powers to join with us in human spaceflight adventures. National space policy too often has been implemented in a stovepipe fashion that makes it difficult to recognize connections between space activities and pressing national challenges. Often, senior policy makers with broad portfolios have not been able to take the time to consider the space program in the broader national context. Rather, policies have been translated into programs by setting budget levels and then expecting agencies to manage to those budgets. The committee believes that the process of aligning roles and responsibilities for space activities, making resource commitments, and coordinating across departments and agencies needs to be carried out at a sufficiently high level so that decisions are made from the perspective of addressing the larger national issues whose resolution space activities can help achieve. How this process is accomplished might change from administration to administration, but the need for an approach that will elevate attention to the proper level remains essential. Organizing to meet national needs. The President of the United States should task senior executive-branch officials to align agency and department strategies; identify gaps or shortfalls in policy coverage, policy implementation, and resource allocation; and identify new opportunities for space-based endeavors that will help to address the goals of both the U.S. civil and national security space programs. The effort should include the Assistant to the President for National Security Affairs and the Assistant to the President for Science and Technology, and should consider the following elements: Coordinating budgetary guidance across federal departments and agencies involved in space activities; Coordinating responsibility and accountability for resource allocations for common services and/or infrastructure; Coordinating responsibility and accountability for stimulating, nurturing, and sustaining a robust space industrial base, including the commercial space industry; Coordinating responsibility and accountability for initiatives to recruit and develop a competent aerospace workforce of sufficient size and talent, anticipating future needs; Identifying, developing, and coordinating initiatives to address long-range technological needs for future programs; Identifying, developing, and coordinating initiatives to establish and strengthen international space relationships; Harmonizing the roles and responsibilities of federal agencies to eliminate gaps and unnecessary duplication in the nation’s space portfolio; and Regularly reviewing coordinated national space strategies and their success in implementing overall national space policy.
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Space Studies Board: Annual Report 2009 5.2 Approaches to Future Space Cooperation and Competition in a Globalizing World: Summary of a Workshop James V. Zimmerman, Rapporteur Summary With the end of the Cold War, space and Earth science research and space exploration were no longer dominated by competition between two superpowers. Numerous countries and regions now have very active space programs, and the number is increasing. These maturing capabilities around the world create a plethora of potential partners for cooperative space endeavors, while at the same time heightening competitiveness in the international space arena. In assessing the effectiveness of specific past and present cooperation or coordination mechanisms and in seeking to determine how best to proceed in the future, it is important to recognize that the world has become more globalized. International cooperation and coordination on both a bilateral and multilateral basis have played a significant role in civil space activities since the beginning of the space age. Generally speaking, cooperation involves two or more countries working together, each contributing to the execution of a single mission. Coordination involves two or more countries that keep each other apprised of their activities in order to minimize duplication of effort and to obtain the maximum return through complementary activities. International cooperation and coordination have occurred extensively in Earth and space science research, Earth applications from space, human spaceflight and microgravity science, and to a lesser extent satellite telecommunications, satellite navigation, and launchers. Currently, most space-faring nations have space-related aspirations that exceed the resources available to them individually. At the same time, more countries are working to enter the field. Thus, it is appropriate to review the models for international cooperation and coordination that have or have not worked in the past to identify the most effective approaches for the future, including how best to involve nations with an emerging space capability. There are also lessons to be learned from the competitive space arena that may have relevance to developing future modes of cooperation. In opening the November 2008 workshop, Space Studies Board chair Charles Kennel noted that the ongoing globalization in today’s world and the current global financial crisis have implications for space. He expressed the opinion that the international order is going to be restructured, with major shifts in international relationships that will impact space. In his view there will therefore be a need for the space community to respond by working to develop a global approach to space. While the workshop’s charge covered both cooperation and competition, workshop discussions tended to focus more on cooperation, given the backgrounds of the majority of participants. WORKSHOP PLENARY DISCUSSIONS Following keynote presentations by former NOAA administrator Conrad Lautenbacher, entitled “Scientific and Technological Cooperation and Competition in a Globalizing World” (Appendix D), and historian Roger Launius of the National Air and Space Museum, entitled “Governmental Space Cooperation and Competition During and After the Cold War—Lessons Learned” (Appendix E), the workshop moved to panel sessions with four panels addressing different aspects of space cooperation and competition. The first panel on lessons learned from previous cooperative efforts emphasized space and Earth science cooperation, with the International Space Station (ISS) as one model; the International Traffic in Arms Regulations (ITAR), seen as a space cooperation inhibitor; and international cooperation within the commercial sector. The second panel discussed lessons learned from past and present competitive activities. Speakers were drawn from commercial launch services and commercial remote sensing sectors. NOTE: “Summary” reprinted from Approaches to Future Space Cooperation and Competition in a Globalizing World: Summary of a Workshop, The National Academies Press, Washington, D.C., 2009, pp. 1-5.
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Space Studies Board: Annual Report 2009 The third panel addressed space and national security. Major issues that surfaced related to ITAR, attitudes of the U.S. Congress with regard to international cooperation, and the implications of seeking to engage China in future cooperative space activities. The fourth panel focused on the potential offered by space cooperation as a tool for the engagement of new and emerging space nations. Particular emphasis was placed on continuing activities within the Global Exploration Strategy/International Space Exploration Coordination Group, U.S.-Japanese space cooperation, and China’s emergence as a major space power. Following panel presentations, workshop participants collectively discussed the issues raised. WORKSHOP DISCUSSION GROUPS Following the plenary discussions, workshop participants were divided into four parallel discussion groups that were each given one of the following topics to address: International space cooperation as a tool for engagement with emerging space power, The role of international cooperation in the future of space exploration, The role of Earth observations in supporting international efforts in climate and sustainability, and New approaches to global space cooperation in a time of limited resources. The views of discussion group participants were reported back to the final plenary session and are summarized below. They do not represent consensus findings or conclusions on the part of the National Research Council, the Space Studies Board, the workshop as a whole, or any other group. Engaging New and Emerging Space Powers in International Cooperation The discussion group on engaging new and emerging space powers in international cooperation observed that new and emerging space powers may desire to cooperate with the United States on space projects for a variety of reasons including: Enhancement of their prestige; Acceleration of their economic and technical development; and Greater access to knowledge, experience, and technology. From a U.S. perspective, the group identified benefits from collaboration that included: Support for U.S. foreign-policy goals; Increased access to key decision makers; Insight into capabilities, approaches, and plans; Identification of new ideas and new technologies; Reduction in U.S. costs; and Expansion of instrument flight opportunities and data analysis capabilities. Opportunities for the Future One particularly valuable effort, the group suggested, could involve the convening of forums through which existing space powers could engage in dialogue with new and emerging space powers. Such forums could provide opportunities to: Improve mutual understanding of capabilities, programs, and plans, Assess the current state of cooperation, Identify potential collaborative programs, Recommend promising mechanisms for continued joint consultations, Promote open participation, and Develop personal and institutional relationships.
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Space Studies Board: Annual Report 2009 The discussion group members, including participants from Europe and Japan, noted that the Space Studies Board might wish to consider implementing such forums and to do so in a collaborative fashion that involves the European Space Science Committee and a counterpart organization in Japan. International Cooperation in the Future of Space Exploration Participants in the discussion group on international cooperation in the future of space exploration observed that with the world becoming increasingly interdependent, space activities need to be conducted in a manner consistent with this reality. For international space activities to offer maximum benefits, they must be conducted in genuine partnerships, where benefits flow to all partners and interdependency underlies the relationships. The discussion group members also observed that increased space collaboration can provide broad benefits to the United States by making space a routine place for all nations to operate (thereby enhancing the security of space assets), by expanding the economic sphere into space, and by demonstrating that the United States is a cooperative society desiring to work productively with all nations (which could improve the U.S. image). Opportunities for the Future The workshop group identified a number of steps that could be taken into account by the United States as it pursues future space exploration projects. These include: Assessing cooperative opportunities on their merits instead of excluding “critical path” roles for potential partners as a matter of policy; Developing a workforce (at all levels) capable of and interested in working on international programs; and Recognizing that U.S. partners need to be able to demonstrate the political and economic benefits of collaboration to the same extent as the United States. The group observed that the ISS program offers opportunities for engaging new and emerging space powers with human spaceflight capabilities and/or interests. China presents a unique opportunity in this regard, the group observed. They added that if the station becomes a tool for engagement, then ISS operations would necessarily have to be extended beyond 2016—a step could provide greater opportunities for current ISS partners to achieve acceptable returns on investments. The consequences of expanding the ISS partnership to include China and the potential impact on NASA of continuing the program beyond 2016 engendered considerable discussion during the workshop, including the broader political context of U.S. engagement with China and the impact on other NASA program areas. International Cooperation in Support of Climate Change and Sustainability Initial discussions in the workshop discussion group on international cooperation in support of climate change and sustainability concerned a redefinition of its title and mandate. The group decided that the topic should be “the role of Earth observations in supporting international efforts in climate change and sustainability,” which would be more consistent with overall workshop objectives. They observed that: Global warming is unequivocal and human actions are contributing to abrupt and irreversible climate changes and impacts; Earth observations are national and global imperatives that are fundamental to monitoring and understanding climate change, achieving sustainability, and protecting our economy and society; and Climate monitoring requires timely access and quality controlled, continuous measurements of the Earth system. Opportunities for the Future The workshop group then elaborated a number of potential “paths forward” in international cooperation which included:
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Space Studies Board: Annual Report 2009 Allocating the necessary resources to establish a national Earth observing system, including vital research and operational elements, as part of a comprehensive global effort; Continuing to provide U.S. leadership and support to the Group on Earth Observations (GEO),1 Engaging other GEO member nations to provide adequate resources for space-based Earth-observation systems; Supporting expanded GEO principles for full and open exchange of national data sets; Pursuing, through the Committee on Earth Observations Satellites (CEOS), a global architecture for continuity and coherence of space segment data sets that includes, for example, virtual satellite constellations from multiple providers; Encouraging, through GEO and CEOS among others, nations to promote open utilization of remote sensing data; Seeking improved communications between GEO and industry through establishment of a mechanism for industry representation in GEO; and Making the public aware of impending challenges posed by and consequences expected from global change as well as the necessity of space-based Earth observations to address those challenges. Approaches to International Cooperation in a Time of Limited Resources The group discussing approaches to international cooperation in a time of limited resources initially considered several factors that might influence future approaches to global space cooperation and coordination, including the following: Additional country partners (e.g., China, India, and other countries), New potential sponsors (philanthropic and military organizations), New opportunities (e.g., space solar power and participatory technologies), and Threats (e.g., global climate change and asteroids). They noted that today’s global environment is different from the past. The growth of space capabilities around the world, including those of new players, means that it is not always clear which country is dominant in a particular sphere of space activity. Opportunities for the Future The group reviewed various current and prospective models for international space cooperation, including the “benchmark” bilateral or multilateral government-to-government cooperation, and the advantages and disadvantages were noted. The group also discussed the potential for collaboration through public/private utilities (such as INTELSAT), military alliances, and philanthropic initiatives. Group participants noted that cooperation initiatives that are based on clear threats (e.g., near Earth objects and climate change) might be better served through the establishment of treaty-based collaborative mechanisms. They also noted three questions that merit further consideration, perhaps as discussion topics in a future Space Studies Board workshop: How will emerging space companies, philanthropic initiatives, and so on, interact with traditional organizations pursuing space cooperation? How will participatory technologies2 be incorporated into space collaboration efforts? Can evolutionary paths and approaches lead to better outcomes for space cooperation (e.g., could the ISS program evolve into a treaty organization and eventually into a public/private utility)? 1 See http://www.earthobservations.org/. 2 “Participatory technologies” refers to the popular Google Sky, Google Mars, and other examples of technological tools used as a means of “seeing” space and “almost being there,” from the three-dimensionality of the Google visualization. It also refers to opportunities to see images sent by the cameras on rovers such as Spirit and Opportunity—you can use your computer and pan around for different camera angles. In the future, perhaps people will be able to propose where they would like a rover to go and virtually “drive it” from their computer. In short, people could virtually be in space.
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Space Studies Board: Annual Report 2009 CONCLUDING OBSERVATIONS During the final workshop plenary session each of the participants offered concluding observations focused on the following themes: Pursuing a dialogue and exploring new opportunities to cooperate with new and emerging space powers. Identifying roles for civil space programs that contribute to broader national goals (space cooperation offers unique opportunities in this regard, several participants noted); Engaging youth in the pursuit of space cooperation; Modifying the U.S. approach to leadership; and Revising ITAR regulations to make them more efficient and effective.
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Space Studies Board: Annual Report 2009 outreach efforts between researchers and NASA, and it should improve the coordination of education efforts between NASA’s Heliophysics Division and its Office of Education. Guidance to Improve the Next Decadal Survey The committee provides eight guidelines to improve the quality of the next decadal survey in solar and space physics. These guidelines are not formal recommendations to NASA, but they do give important advice for negotiating the statement of task for the next decadal survey and its committee. Guideline 1: Schedules for future NASA roadmapping exercises should be phased to follow future NRC decadal surveys and midterm assessments. Guideline 2: The next decadal survey should reconsider any missions from the 2003 decadal survey that have not begun development at the time of the next decadal survey. Guideline 3: The next decadal survey should incorporate cost thresholds beyond which NASA must consult with the community through a formal mechanism (such as committees of the NASA Advisory Council or other independent, external, community priority-setting bodies) to review a mission’s continued priority. Guideline 4: The next decadal survey should develop a methodology to preserve mission coordination when mission coordination is equal to or greater than the importance of the missions themselves. Guideline 5: In addition to refining cost estimates for mission development, the next decadal survey should improve cost estimates for mission operations and data analysis. Guideline 6: The next decadal survey should explicitly budget for all recommendations, not just those associated with missions, mission operations and data analysis, and research. Guideline 7: The next decadal survey should maintain the practice of providing a prioritized consensus list of program recommendations. Guideline 8: The next decadal survey should include a sufficient number of scientists with spaceflight investigation experience from each of the relevant subdisciplines.
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Space Studies Board: Annual Report 2009 5.7 Radioisotope Power Systems: An Imperative for Maintaining U.S. Leadership in Space Exploration A Report of the Ad Hoc Radioisotope Power Systems Committee Summary For nearly 50 years, the United States has led the world in the scientific exploration of space. U.S. spacecraft have circled Earth, landed on the Moon and Mars, orbited Jupiter and Saturn, and traveled beyond the orbit of Pluto and out of the ecliptic. These spacecraft have sent back to Earth images and data that have greatly expanded human knowledge, though many important questions remain unanswered. Spacecraft require electrical energy. This energy must be available in the outer reaches of the solar system where sunlight is very faint. It must be available through lunar nights that last for 14 days, through long periods of dark and cold at the higher latitudes on Mars, and in high-radiation fields such as those around Jupiter. Radioisotope power systems (RPSs) are the only available power source that can operate unconstrained in these environments for the long periods of time needed to accomplish many missions, and plutonium-238 (238Pu) is the only practical isotope for fueling them. The success of historic missions such as Viking and Voyager, and more recent missions such as Cassini and New Horizons, clearly show that RPSs—and an assured supply of 238Pu—have been, are now, and will continue to be essential to the U.S. space science and exploration program. Multi-Mission Radioisotope Thermoelectric Generators (MMRTGs) are the only RPS currently available. MMRTGs convert the thermal energy that is released by the natural radioactive decay of 238Pu to electricity using thermocouples. This is a proven, highly reliable technology with no moving parts. The Advanced Stirling Radioisotope Generator (ASRG) is a new type of RPS that is still being developed. An ASRG uses a Stirling engine (with moving parts) to convert thermal energy to electricity. Stirling engine converters are much more efficient than thermocouples. As a result, ASRGs produce more electricity than MMRTGs, even though they require only one-fourth as much 238Pu. It remains to be seen, however, when development of a flight-qualified ASRG will be completed. THE PROBLEM Plutonium-238 does not occur in nature. Unlike 239Pu, it is unsuitable for use in nuclear weapons. Plutonium-238 has been produced in quantity only for the purpose of fueling RPSs. In the past, the United States had an adequate supply of 238Pu, which was produced in facilities that existed to support the U.S. nuclear weapons program. The problem is that no 238Pu has been produced in the United States since the Department of Energy (DOE) shut down those facilities in the late 1980s. Since then, the U.S. space program has had to rely on the inventory of 238Pu that existed at that time, supplemented by the purchase of 238Pu from Russia. However, Russian facilities that produced 238Pu were also shut down many years ago, and the DOE will soon take delivery of its last shipment of 238Pu from Russia. The committee does not believe that there is any additional 238Pu (or any operational 238Pu production facilities) available anywhere in the world. The total amount of 238Pu available for NASA is fixed, and essentially all of it is already dedicated to support several pending missions—the Mars Science Laboratory, Discovery 12, the Outer Planets Flagship 1 (OPF 1), and (perhaps) a small number of additional missions with a very small demand for 238Pu. If the status quo persists, the United States will not be able to provide RPSs for any subsequent missions. Reestablishing domestic production of 238Pu will be expensive; the cost will likely exceed $150 million. Previous proposals to make this investment have not been enacted, and cost seems to be the major impediment. However, regardless of why these proposals have been rejected, the day of reckoning has arrived. NASA is already making mission-limiting decisions based on the short supply of 238Pu. NASA is stretching out the pace of RPS- NOTE: “Summary” reprinted from Radioisotope Power Systems: An Imperative for Maintaining U.S. Leadership in Space Exploration, The National Academies Press, Washington, D.C., 2009, pp. 1-4.
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Space Studies Board: Annual Report 2009 powered missions by eliminating RPSs as an option for some missions and delaying other missions that require RPSs until more 238Pu becomes available. Procuring 238Pu from Russia or other foreign nations is not a viable option because of schedule and national security considerations. Fortunately, there are two viable approaches for reestablishing production of 238Pu in the United States. Both of these approaches would use existing reactors at DOE facilities at Idaho National Laboratory and Oak Ridge National Laboratory with minimal modification, but a large capital investment in processing facilities would still be needed. Nonetheless, these are the best options in terms of cost, schedule, and risk for producing 238Pu in time to minimize the disruption in NASA’s space science and exploration missions powered by RPSs. IMMEDIATE ACTION IS REQUIRED On April 29, 2008, the NASA administrator sent a letter to the secretary of energy with an estimate of NASA’s future demand for 238Pu.1 The committee has chosen to use this letter as a conservative reference point for determining the future need for RPSs. However, the findings and recommendations in this report are not contingent on any particular set of mission needs or launch dates. Rather, they are based on a conservative estimate of future needs based on various future mission scenarios. The estimate of future demand for 238Pu (which is about 5 kg/year) is also consistent with historic precedent. The orange line [hollow square data points] in Figure S.1 shows NASA’s cumulative future demand for 238Pu in a best-case scenario (which is to say, a scenario in which NASA’s future RPS-mission set is limited to those missions listed in the NASA administrator’s letter of April 2008, the 238Pu required by each mission is the smallest amount listed in that letter, and ASRGs are used to power OPF 1). The green line [solid square data points] shows NASA’s future demand if the status quo persists (which is to say, if OPF 1 uses MMRTGs). Once the DOE is funded to reestablish production of 238Pu, it will take about 8 years to begin full production of 5 kg/year. The red and blue lines [triangular data points] in Figure S.1 show the range of future possibilities for 238Pu balance (supply minus demand). A continuation of the status quo, with MMRTGs used for OPF 1 and no production of 238Pu, leads to the largest shortfall, and the balance curve drops off the bottom of the chart. The best-case scenario, which assumes that OPF 1 uses ASRGs and DOE receives funding in fiscal year (FY) 2010 to begin reestablishing its ability to produce 238Pu, yields the smallest shortfall (as little as 4.4 kg). However, it seems unlikely that all of the assumptions that are built into the best-case scenario will come to pass. MMRTGs are still baselined for OPF 1, there remains no clear path to fight qualification of ASRGs, and FY 2010 funding for 238Pu production remains more a hope than an expectation. Thus, the actual shortfall is likely to be somewhere between the best-case curve and the status-quo curve in Figure S.1, and it could easily be 20 kg or more over the next 15 to 20 years. It has long been recognized that the United States would need to restart domestic production of 238Pu in order to continue producing RPSs and to maintain U.S. leadership in the exploration of the solar system. The problem is that the United States has delayed taking action to the point that the situation has become critical. Continued inaction will exacerbate the magnitude and the impact of future 238Pu shortfalls, and it will force NASA to make additional, difficult decisions that will reduce the science return of some missions and postpone or eliminate other missions until a source of 238Pu is available. The schedule for reestablishing 238Pu production will have to take into account many factors, such as construction of DOE facilities, compliance with safety and environmental procedures, and basic physics. This schedule cannot be easily or substantially accelerated, even if much larger appropriations are made available in future years in an attempt to overcome the effects of ongoing delays. The need is real, and there is no substitute for immediate action. HIGH-PRIORITY RECOMMENDATION. Plutonium-238 Production. The fiscal year 2010 federal budget should fund the Department of Energy (DOE) to reestablish production of 238Pu. As soon as possible, the DOE and the Office of Management and Budget should request—and Congress should provide—adequate funds to produce 5 kg of 238Pu per year. NASA should issue annual letters to the DOE defining the future demand for 238Pu. 1 Letter from the NASA Administrator Michael D. Griffin to Secretary of Energy Samuel D. Bodman, April 29, 2008 (reprinted in Appendix C).
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Space Studies Board: Annual Report 2009 FIGURE S.1 Potential 238Pu demand and net balance, 2008 through 2028. DEVELOPMENT OF A FLIGHT-READY ADVANCED STIRLING RADIOISOTOPE GENERATOR Advanced RPSs are required to support future space missions while making the most out of whatever 238Pu is available. Until 2007, the RPS program was a technology development effort. At that time, the focus shifted to development of a flight-ready ASRG, and that remains the current focus of the RPS program. The program received no additional funds to support this new tasking, so funding for several other important RPS technologies was eliminated, and the budget for the remaining RPS technologies was cut. As a result, the RPS program is not well balanced. Indeed, balance is impossible given the current (FY 2009) budget and the focus on development of flight-ready ASRG technology. However, the focus on ASRG development is well aligned with the central and more pressing issue that threatens the future of RPS-powered missions: the limited supply of 238Pu. The RPS program should continue to support NASA’s mission requirements for RPSs while minimizing NASA’s demand for 238Pu. NASA should continue to move the ASRG project forward, even though this has come at the expense of other RPS technologies. Demonstrating the reliability of ASRGs for a long-life mission is critical, but it has yet to be achieved. The next major milestones in the advancement of ASRGs are to freeze the design of the ASRG, conduct system testing that verifies that all credible life-limiting mechanisms have been identified and assessed, and demonstrate that ASRGs are ready for flight. In lieu of any formal guidance or requirements concerning what constitutes
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Space Studies Board: Annual Report 2009 flight readiness, ongoing efforts to advance ASRG technology and demonstrate that it is flight ready are being guided by experience gained from past programs and researchers’ best estimates about the needs and expectations of project managers for future missions. While this approach has enabled progress, the establishment of formal guidance for flight certification of RPSs in general and ASRGs in particular would facilitate the acceptance of ASRGs as a viable option for deep-space missions and reduce the impact that the limited supply of 238Pu will have on NASA’s ability to complete important space missions. RECOMMENDATION. Flight Readiness. The RPS program and mission planners should jointly develop a set of flight-readiness requirements for RPSs in general and Advanced Stirling Radioisotope Generators in particular, as well as a plan and a timetable for meeting the requirements. RECOMMENDATION. Technology Plan. NASA should develop and implement a comprehensive RPS technology plan that meets NASA’s mission requirements for RPSs while minimizing NASA’s demand for 238Pu. This plan should include, for example: A prioritized set of program goals. A prioritized list of technologies. A list of critical facilities and skills. A plan for documenting and archiving the knowledge base. A plan for maturing technology in key areas, such as reliability, power, power degradation, electrical interfaces between the RPS and the spacecraft, thermal interfaces, and verification and validation. A plan for assessing and mitigating technical and schedule risk.,., RECOMMENDATION. Multi-Mission RTGs. NASA and/or the Department of Energy should maintain the ability to produce Multi-Mission Radioisotope Thermoelectric Generators. HIGH-PRIORITY RECOMMENDATION. ASRG Development. NASA and the Department of Energy (DOE) should complete the development of the Advanced Stirling Radioisotope Generator (ASRG) with all deliberate speed, with the goal of demonstrating that ASRGs are a viable option for the Outer Planets Flagship 1 mission. As part of this effort, NASA and the DOE should put final-design ASRGs on life test as soon as possible (to demonstrate reliability on the ground) and pursue an early opportunity for operating an ASRG in space (e.g., on Discovery 12).
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Space Studies Board: Annual Report 2009 5.8 Uncertainty Management in Remote Sensing of Climate Data: Summary of a Workshop Martha McConnell and Scott Weidman, Rapporteurs Introduction Great advances have been made in our understanding of the climate system over the past few decades, and remotely sensed data have played a key role in supporting many of these advances. Improvements in satellites and in computational and data-handling techniques have yielded high quality, readily accessible data. However, rapid increases in data volume have also led to large and complex datasets that pose significant challenges in data analysis (NRC, 2007). Uncertainty characterization is needed for every satellite mission and scientists continue to be challenged by the need to reduce the uncertainty in remotely sensed climate records and projections. The approaches currently used to quantify the uncertainty in remotely sensed data, including statistical methods used to calibrate and validate satellite instruments, lack an overall mathematically based framework. An additional challenge is characterizing uncertainty in ways that are useful to a broad spectrum of end-users. In December 2008, three standing committees of the National Academies held a workshop to survey how statisticians, climate scientists, and remote sensing experts might address the challenges of uncertainty management in remote sensing of climate data. The emphasis of the workshop was on raising and discussing issues that could be studied more intently by individual researchers or teams of researchers, and on setting the stage for possible future collaborative activities. Issues and questions that were addressed at the workshop include the following: What methods are currently used to compare time series at single points in space with instantaneous but sparsely sampled area averages to “validate” remotely sensed climate data? Are there more sophisticated or advanced methods that could be applied to improve validation tools or uncertainty estimates? Are there alternative means of measuring the same phenomena to confirm the accuracy of satellite observations? How can fairly short-term, spatially dense remote sensing observations inform climate models operating at long time scales and relatively coarse spatial resolutions? Are there remotely sensed data that could, through the use of modern statistical methods, be useful for improving climate models or informing other types of climate research? What are the practical and institutional barriers (e.g., lack of qualified statisticians working in the field) to making progress on developing and improving statistical techniques for processing, validating, and analyzing remotely sensed climate data? In her introductory remarks at the workshop, planning team chair Amy Braverman from the Jet Propulsion Laboratory presented Table 1-1 to illustrate how statistical methods (rows) can help address three major challenges in the use of remotely sensed climate data (the columns). The first of these three major challenges is the validation of remote sensing retrievals. When a remote sensing instrument retrieves a measurement that is used to infer a geo-physical value (e.g., atmospheric temperature), uncertainties exist both in the measured values and in the statistical model used to validate the remotely sensed parameter. The second challenge is improving the representation of physical processes within all types of climate models. Workshop participants stressed the need to better represent physical processes within global earth system models, a critical component to projecting future climate accurately, reducing uncertainty, and ultimately aiding policy decisions. The third major challenge in climate research where statistics plays an important role is aggregating the observed and modeled knowledge, each with their associated uncertainties, to develop a better understanding of the climate system that can lead to useful predictions. Complex and multifaceted relationships in the physics of the climate system contribute uncertainty over and above that which is normally present in making inferences from massive, spatio-temporal data. Isolating and quantifying these uncertainties in the face of multiple scales of spatial and temporal resolution, nonlinear relationships, NOTE: “Introduction” reprinted from Uncertainty Management in Remote Sensing of Climate Data: Summary of a Workshop, The National Academies Press, Washington, D.C., 2009, pp. 1-10.
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Space Studies Board: Annual Report 2009 feedbacks, and varying levels of a priori knowledge poses major challenges to achieving the linkages shown in Table 1-1. A formal statistical model that articulates relationships among both known and unknown quantities of interest and observations can sharpen the picture and make the problem more tractable. Random variables can represent uncertain quantities and describe relationships through joint and conditional distributions. Random variables can also be infused into systems of physical equations, to carry information about uncertainties along with information provided by physical knowledge. Crafting such hybrid physical-statistical models to capture the essence of our understanding is not easy. The climate system is inherently nonlinear and includes feedback loops where variables directly and indirectly affect one another. Figure 1-1, presented at the workshop by William Rossow from the City College of New York, is a simple diagram of the energy and water cycles of the climate system that demonstrates how the system is interconnected. In order to gain a true understanding of climate feedbacks it is important to understand multiple variables in the climate system and their interactions. Clouds and precipitation, for example, play a crucial role in both the water cycle and the earth’s energy balance, affecting the sources and sinks of heat in the climate system. The release of latent heat during precipitation events provides energy that drives atmospheric circulations, and, in turn, atmospheric circulation processes that affect the distribution of water vapor and the formation of clouds have a pronounced effect on the transfer of radiation through the atmosphere. Therefore, analyzing the interrelationships between multiple variables in the climate system is key to understanding processes of interest. Large volumes of remote sensing data are available to assist in refining models of physical systems like that shown in Figure 1-1. Data provide information about physical mechanisms at work in the atmosphere, and also about the uncertainties or gaps in our understanding of how those mechanisms operate. To make use of data in this way, however, requires that inherent uncertainties and biases in the data themselves be known and quantified. Therefore, the problem requires a holistic approach to uncertainty management beginning with data collection and validation strategies that are cognizant of the uses of the data. These challenges can be addressed in two ways: By identifying data collection and analysis methods that minimize the uncertainties; and By identifying the contributions to uncertainty at the various steps in collection and analysis, thereby pointing out the most promising targets for improvement. TABLE 1-1 Three Major Challenges in the Use of Remotely Sensed Climate Data (Columns) and Three Roles Played by Statistical Methods (Rows) Challenge: Validation of remote sensing retrievals Challenge: Improving physical representations and understanding Challenge: Extrapolating to future climate predictions Role for statistics: Clarify and characterize sources of uncertainty in remote sensing data Characterize spatio-temporal mismatches, retrieval algorithm differences; address sparseness or absence of ground truth Develop new statistical methods to make the most of new data types to address new science questions Maximize value of limited data and hard-to-formalize assumptions about relationships among past, present, and future Role for statistics: Develop statistical methods to quantify and reduce uncertainty Develop formal statistical error measures for both bias and variance Develop new methods to exploit massive datasets in an inferential setting Develop formalisms for combining output from different models in light of available data Role for statistics: Provide an overarching framework Overcome mismatches by statistical modeling of relationships between observed and unobserved quantities. Pose problems as formal questions of statistical inference Combine physical and statistical models SOURCE: Table courtesy of Amy Braverman, JPL.
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Space Studies Board: Annual Report 2009 FIGURE 1-1 Schematic of energy and water cycles. Red represents transfers of energy while blue lines show transfers of water. Figure courtesy of William Rossow, City College of New York. Uncertainty quantification, in the broadest sense, is to account for not only uncertainty in individual parameters within the models that are used, but also to account for the uncertainty inherent in the actual models themselves, which are only approximate representations of physical processes. Workshop participants emphasized that improving physical process representation is critical for both improving climate models and for better characterizing their uncertainties. Statistics can contribute to solving this problem by moving beyond linear analysis for individual parameters to capture more complex relationships that have a physical meaning. A good statistical model is built in a way that captures some of the physical processes that control elements of the climate system, or alternative hypotheses about those processes. The classical method, described at the workshop, for characterizing uncertainty in earth science modeling is through sensitivity analysis. Simply, this method includes changing parameter values in a model to learn how much that parameter affects the model output. This method does not account for the possibility that more than one process represented in the model might rely on the parameter itself, which will affect the uncertainty estimate. In addition, the compounding effect of different sources of uncertainty on different parameters is difficult to quantify through sensitivity analyses. Alternative statistical approaches define uncertainty through joint probability distributions of parameters. While it is difficult to use this approach to identify the correct parameters and distributions when datasets are small, advances in data collection, management, and processing technologies are increasingly resulting in large datasets. Statistical distributions and their parameters can be estimated accurately when large volumes of data are available. Scientists in the satellite era have this luxury, but are concomitantly faced with massive data volumes that create challenges for processing and analysis techniques. In principle, large, complex, and detailed datasets offer the promise of new knowledge from which to better understand the climate system. Statistical methods that are developed specifically for new data types can better exploit these large, complex datasets that traditional methods (i.e., sensitivity analysis) cannot. Understanding the uncertainties of different processes in the climate system requires a variety of approaches. Collaborations involving climate scientists and statisticians were identified at the workshop as an effective way to promote the development of targeted new methods that would aid the science community to question all aspects of the data, and geophysical and statistical models. Workshop participants also remarked that modern statistical methods can be useful for fusing data from two different instruments, which is a more challenging problem than
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Space Studies Board: Annual Report 2009 is generally appreciated. For example, data assimilation techniques are one approach to addressing the spatial and temporal mismatch between models and observations (Daley, 1991; Luo et al., 2007). As described by workshop participant Anna Michalak from the University of Michigan, such approaches need to account for the spatial and temporal structure of the dataset to allow a better understanding of the physical processes that make up the climate system. WHY WORRY ABOUT STATISTICAL STRUCTURE: AN EXAMPLE FROM MODELING SNOW DEPTH Anna Michalak at the University of Michigan described how the statistical properties in remote sensing datasets offer both a challenge and an opportunity. For example, understanding and accounting for statistical dependence, including spatial and temporal correlations, can improve the utility of observational datasets. The opportunity is that by skillfully handling these complexities, we can better take advantage of the full information content of the available data, and use this information to guide high-payout improvements in models of the Earth system. In some cases, statisticians and earth scientists use similar techniques to evaluate, and take advantage of, the spatial and temporal structure of observations of environmental parameters. For example, spatial statistical techniques allow one to interpolate (the earth scientist’s term) or predict (the statistician’s term) the value of specific environmental parameters at unsampled locations. The vast majority of environmental parameters (e.g., clouds, precipitation, winds) exhibit spatial and/or temporal correlation, with associated characteristics of scales of variability. As stated by Tobler as the “first law of geography”: “Everything is related to everything else, but near things are more related than distant things” (Tobler, 1970). Both statisticians and earth sciences have used quantitative tools to assess the spatial autocorrelation exhibited by sampled data. Both use variograms and/or covariance functions to quantify the degree of spatial autocorrelation. An accurate assessment of the spatial variability of observed parameters can be used to better understand the underlying physical processes. Figure 1-2 illustrates how understanding and exploiting the spatial and temporal structure of data can be useful. In this example, a limited number of measurements that are clustered in a non-ideal way are used to estimate the mean snow depth in a valley. Simply averaging the ten measurements of snow depth does not provide a good representation of mean snow depth. Instead, the clustered observations in the left portion of the valley clearly need to be weighted less relative to the isolated observation in the right region. However, how much weight should be assigned to each data point? Spatial statistics methods can be used to determine the degree of spatial variability in the snow-depth distribution based on an analysis of how similar nearby measurements are to one another, and how dissimilar far-away measurements are to one another. This information, in turn, can be used to quantify the optimal weights to be assigned to each measurement. This simple method in spatial statistics allows one to calculate an unbiased estimate of mean snow depth in the valley based on an uneven distribution of measurements. In Figure 1-3, we look at a hypothetical dataset describing snow depth as a function of elevation, and assuming that the snow depth is also autocorrelated in space (top panel). These synthetic data were generated in such a way that, in reality, there is no overall trend of snow depth with elevation, and any observed trend is therefore the result of randomness introduced in generating the data. This hypothetical dataset is then used to test whether two competing approaches are able to correctly conclude that there is no relationship between snow depth and elevation (middle panel). In the first approach (red line), classical linear regression is used, which ignores the spatial correlation in the data. In the second approach (green line), the spatial correlation is accounted for in the estimation process. In the example shown in the figure, the classical approach incorrectly rejects the null hypothesis that there is no trend between snow depth and elevation, whereas the approach based on spatial statistics correctly does not reject this hypothesis at the 95 percent confidence level. As the experiment is repeated multiple times with new synthetic data (bottom panel), we observe that the linear regression approach incorrectly concludes that there is a trend between elevation and snow depth approximately 20 percent of the time, which is much too high given that the test was run in a way that should have yielded only a 5 percent chance of incorrectly concluding that there was a trend. The approach that accounts for spatial correlation, concludes that there is a trend 5 percent of the time, as expected. Overall, this example illustrates that statistical approaches that ignore spatial and/or temporal correlation inherent in environmental data carry with them an increased risk of erroneously concluding that significant relationships exist between physical phenomena (snow depth and elevation, in this case), and, more generally, yield biased estimates due to their assumption of independent observations.
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Space Studies Board: Annual Report 2009 FIGURE 1-2 Example of sampling snow depth in a watershed. Top: aerial map of an alpine basin with sample locations Bottom: snow depth at sampling location versus distance from the left edge of the valley. The red line represents the biased estimate of average snow depth obtained from a simple average of the available observations. The green line represents the unbiased estimate obtained by assigning weights to the observations based on an understanding of the scales of spatial variability of the snow depth in the valley. Figure courtesy of Anna Michalak, University of Michigan. Original figure by Tyler Erickson, Michigan Tech Research Institute.
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Space Studies Board: Annual Report 2009 FIGURE 1-3 Hypothetical data on snow depth as a function of elevation. Top: illustrates one case of the generated data, and the estimated slope between snow depth and elevation, using simple linear regression (red line), and an approach that accounts for the spatial correlation of the data (green line). Middle: illustrates the probability distribution of the trend of snow depth with elevation using the two approaches. Bottom: demonstrates that if the experiment were repeated many times, one would erroneously conclude that there was a relationship between snow depth and elevation too often if using simple linear regression. Figure courtesy of Anna Michalak, University of Michigan. Original figure by Tyler Erickson, Michigan Tech Research Institute.