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Earth Observations from Space: The First 50 Years of Scientific Achievements 1 Introduction Over the past 50 years, the United States has developed impressive capabilities for observing Earth from space-based platforms. Global observations of a wide range of geophysical and biological parameters have provided unprecedented insight into how the Earth system functions and have led to many fundamental scientific advances. The capacity to forecast and project weather, climate, and environmental hazards has benefited extensively from satellite-based Earth observations. Satellite observations have literally transformed the way we view the planet. Earth observations from space have provided the information needed to verify and complete our understanding of how ozone chemistry in the stratosphere controls the infamous polar ozone hole; how ocean currents, temperatures, and atmospheric processes are coupled to the El Niño-Southern Oscillation; how snow cover affects water cycle dynamics; and how numerous global and regional factors influence sea level change. The Earth science community is devoting significant efforts to planning future observations and research to be conducted with space-based platforms. One important element of this effort is the recent “decadal survey” led by the National Academies: Earth Science and Applications from Space: Urgent Needs and Opportunities to Serve the Nation (NRC 2005) and Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond (NRC 2007a). These are two forward-looking reports funded jointly by the National Aeronautics and Space Administration (NASA), U.S. Geological Survey, and National Oceanic and Atmospheric Administration (NOAA). The reports provide guidance to the three agencies regarding future priorities and briefly summarize the value of satellite observations to the well-being of society. However, the continued availability of environmental satellite data in the future is jeopardized because of budgetary constraints and programmatic difficulties (NRC 2005, 2007a). Consequently, the reports recommend a renewal of the commitment to support observations from space in view of the scientific and societal challenges of understanding and managing natural resources over the coming decades. In addition to the decadal survey, NASA asked the National Academies to look back on the history of space-based observations of Earth to illustrate the contributions to the scientific enterprise to date (Box 1.1). THE STUDY’S APPROACH The committee relied on the relevant literature, its own collective experience, and input from the Earth science community to compile an extensive list of accomplishments resulting from Earth observations from space. Using its expert judgment, the committee chose a subsample of the major accomplishments that are compelling and illustrative to convey the extent to which satellite observations have revolutionized the way people view, understand, and study Earth. The committee did not attempt to provide a comprehensive inventory of accomplishments resulting from satellite information and recognizes the inherent bias of composing any selective list. Nevertheless, the committee believes that any other group of Earth scientists would have provided a compilation with considerable overlap with the one presented in this report, in part because committee members were selected with careful consideration to balancing expertise. In addition to its own expertise, the committee invited other experts to contribute in a variety of ways: the committee invited presentations during a series of meetings, held a town hall session at the 2006 Annual Meeting of the American Geophysical Union, posted a call for input on the committee’s website, and approached the following Earth science communities with a solicitation for contributions on accomplishments from Earth satellite observations: members of the National Academy of Sciences and National Academy of Engineering,
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Earth Observations from Space: The First 50 Years of Scientific Achievements BOX 1.1 Statement of Task This study documents specific scientific accomplishments resulting from the nation’s research and development of space-based Earth observational capabilities. The study committee sought broad community input to identify examples of important accomplishments, in part by drawing on the expertise of the various entities within the National Academies and also involving those scientific communities that develop and use remote sensing observations of the Earth. The study’s main objective is to document, using examples and explanation, how satellite observations uniquely contributed to scientific understanding of the atmosphere, ocean, land, biosphere, and cryosphere. As secondary objectives, the study also addresses how satellite observations have contributed to the ability to predict variations in the Earth system (e.g., weather, climate variability, water availability, earthquakes, volcanoes, and tsunamis) and comments on opportunities to improve future Earth science research enabled by the vantage point of space. To the extent possible, the committee organizes its comments to correspond to NASA’s seven Earth science foci: (1) atmospheric composition; (2) carbon cycle and ecosystems; (3) climate variability and change; (4) earth surface and interior structure; (5) weather; (6) water and energy cycles; and (7) Sun-Earth connection. members of relevant boards within the National Academies, recipients of the quarterly newsletter of the National Academies’ Board on Atmospheric Sciences and Climate, and members of relevant scientific e-mail distribution lists. This report begins with a brief early history of the evolution of Earth observations from space (Chapter 2). In subsequent chapters the committee presents examples of major scientific accomplishments that have transformed and contributed to the Earth sciences. The committee considered as major accomplishments only scientific advances that resulted in a new discovery, transformative science, proving or disproving an important theory, opening new major research venues, or providing significant societal benefits. These accomplishments are described in Chapters 3 to 11. In the final chapter (Chapter 12), the committee summarizes conclusions drawn from these major accomplishments and highlights opportunities to improve future Earth science research enabled from the vantage point of space.