Satellite Observations to Benefit Science and Society: Recommended Missions for the Next Decade (2008)

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An Integrated Strategy Satellite Observations to Benefit Science and Society N atural and human-induced changes in the Earth system—from our planet’s interior to the land surface, atmosphere, and oceans—affect all aspects of life. If we are to understand and respond to these changes, we need a foundation of observations collected from the land, sea, air, and space, integrated for maximum usefulness in forecast models and other tools for decision making. The United States has made great strides in building and deploying a sophisticated set of Earth- monitoring satellites. In 2004, the National Aeronautics and Space Administration (NASA) com- pleted its Earth Observing System (see facing page), whose centerpiece is three multi-instrumented spacecraft—Terra, Aqua, and Aura—that together provide data for characterizing most of the major Earth system components. For decades, Earth’s landscape has been studied and documented through the Landsat mission, a long-term collaboration between NASA and the U.S. Geological Survey (USGS). Steady improvement in U.S. weather forecasts and climate projections is due in large part to the network of operational satellites managed by the National Oceanic and Atmospheric Administration (NOAA) and the NASA research satellite fleet. But this extraordinary legacy of global observations and benefits is now in serious danger. Many NASA satellites are well past their originally projected lifespan. Funding pressures are affect- ing plans for operational and research missions at both NASA and NOAA. Between 2006 and 2010 the overall number of U.S. space-based sensors will likely decrease by 35 to 40 percent (see graph on facing page). As a result, forecasts of hurricanes and other severe weather events could suffer, and major gaps may develop in some of the data sets most crucial to monitoring the Earth system and detecting changes in global climate. In 2004, NASA, NOAA, and the USGS asked the National Research Council to conduct a decadal survey of the Earth sciences community. The charge was to recommend a prioritized list of flight missions and supporting activities for space-based Earth observation over the next decade (through the 2010s) and to identify key factors in planning for the decade beyond (into the 2020s). This booklet highlights the key points made in the final report of the survey, Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond (available at http://books.nap.edu/catalog.php?record _id=11820). The study was led by the Committee on Earth Science and Applications from Space: A Community Assessment and Strategy for the Future, a group of experts from the natural and social sciences that drew on the work of seven crosscutting panels as well as input from more than 100 community members. As discussed in the survey report, scientific and technical advances make it possible to design a highly productive and integrated suite of satellite-based Earth sensors, capable of providing observations that address a broad range of societal needs. The desire for an integrated observing capability reflects both the increasingly interdisciplinary nature of Earth science and the growing complexity and interrelated nature of the knowledge and information required to meet pressing national needs. Our Earth observing system must also become more efficient to meet these needs within challenging budgetary constraints. The needed capabilities can be achieved as long as up- coming missions are coordinated and structured to complement each other and timed to ensure an unbroken record of key environmental variables. Otherwise, there is a serious risk that important yet aging capabilities will go unreplaced, that potential benefits to society will go unrealized, and that the United States will lose its global standing as a leader in Earth observation.  

Earth Science and Applications from Space  Critical Areas for Earth System Observing Improving weather and climate forecasts European agencies have overtaken their U.S. counterparts in an array of pivotal capabilities, such as 3- to 10-day weather forecasts. New observing tools are critically needed, along with enhanced computing capacity, improved atmospheric models, and tech- niques for assimilating the new data into those models. Protecting against solid-Earth hazards Scientists who study the solid Earth are hampered by a lack of data, much like weather forecasters before the satellite era. Scientists cannot reliably tell which tectonic faults are most likely to rupture and produce earthquakes and tsunamis. They are also constrained in their ability to detect and inter- pret precursors of volcanic eruptions and landslides. Ensuring our water resources The nation’s water supply is of paramount importance to econom- ic development, public health and safety, food production, and recreation. Severe drought over the last few years has struck parts of the West and Southwest where population growth is among the nation’s most rapid. Yet our ability to observe, predict, and adapt to large variations in the hydrologic cycle is inadequate. Mindful of these issues, the committee thus offers the following overarching recommendation: The U.S. government, working in concert with the private sector, academe, the public, and its inter- national partners, should renew its investment in Earth-observing systems and restore its leadership in Earth science and applications. The committee and its panels assert that the effort to obtain practical benefits for humankind can and should play an equal role with the quest to acquire new knowledge about Earth. The overarching objective is a program of science and applications that will protect life and property, enhance economic competitiveness, address profound scientific questions, and assist in the stewardship of our home planet for present and future generations. In support of this vision, the committee recommends a set of 17 Earth observing missions, summarized on pages 8 and 9 of this booklet and described in more detail on pages 10–26. The effort to select and prioritize these missions, as discussed on pages 5–7, involved researchers from an unusually broad set of specialties—geology, oceanography, atmospheric science, ecology, and others. Bringing representatives of these disciplines together was itself a landmark effort, as many of the disciplines had no tradition of working together to forge a set of common research priorities. 

Earth Science and Applications from Space  Maintaining healthy, productive oceans Satellite measurements have revolutionized our understanding of ocean circulation, biology, and interactions with the atmosphere. Many of the sources of these measurements, however, are now at risk because of budget constraints and programmatic choices. Climate change brings new risks for marine life due to ocean warming, changes in circulation, and acidification from increased atmospheric carbon. Assessing and mitigating climate change There are major weaknesses in national and global systems for monitoring climate, and there is no plan for producing a benchmark record of critical variables. Reliable global data are required to test difficult and important research questions, such as how clouds and radiation will interact in a warming climate. Also, nations attempting to regulate and manage their greenhouse emissions need regional data on carbon sources and sinks. Protecting ecosystems Space-borne sensors have helped to quantify dramatic changes to Earth’s surface, including the conversion of more than 20 percent of land areas to cropland, the loss of half the world’s wetlands and mangrove forests, and the clearing of some 25 percent of the planet’s forests. Yet more data are needed to answer key questions. For example, we lack adequate region-by- region estimates of total biomass and how it is changing. Improving human health Decision makers in public health now use satellite-derived data and infor- mation on land, oceans, weather, climate, and atmospheric pollutants. With improved satellite observations, specialists will be able to detect health- threatening environmental change more quickly, identify areas at risk in more detail, and carry out targeted interventions to preserve life and health. The survey report reflects the committee’s best judgment—informed by the work of the cross- cutting panels and discussion with the scientific community—about which Earth observation mis- sions are most important for developing and sustaining the Earth system enterprise. Participants strove to create a program of integrated and complementary observations that will remain robust despite inevitable program changes due to budgetary considerations as well as evolving scientific and societal needs. Missions were selected and phased so as to produce a balanced and integrated program, and the overall range of observations was carefully chosen to accommodate a variety of research goals and provide important societal benefits. Obtaining the necessary range of continuous observations, rather than implementing individual missions, is the top priority. To achieve a fully integrated system capable of providing the desired scientific and societal benefits, the observational tools recommended in the survey report cannot stand alone. They must be part of an Earth information system that connects satellite-retrieved data to forecasting models, information dissemination tools, and other important components. The committee also recommends that the prioritized missions be integrated with in situ observational systems and accompanied by a strong program of Earth science research and analysis. Steps in these directions are discussed on pages 27–31. 

Earth Science and Applications from Space  Earth Sensing to inform society Hurricane Katrina The nation’s worst natural disaster in modern times, Katrina was respon- sible for more than 1,700 deaths, more than $100 billion in damage, and countless other impacts on southeast Louisiana and coastal Mississippi. The human toll could have been far worse were it not for timely and accurate warnings from NOAA, based on computer models that incor- porated space- and aircraft-based observations. Forecasters also con- sulted new data sources recently incorporated into forecast models, such as upper-ocean heat content derived from satellite observations. For example, altimetry readings from NASA satellites showed that the sea- surface height along Katrina’s path in the central Gulf of Mexico was up to 70 centimeters above average, a sign of unusually deep warm water that may have contributed to the hurricane’s growth to Category 5 status. Although Katrina’s track was well predicted, forecasts of the location and magnitude of the storm surge were less accurate, indicating the need for continued research and better observations. Following Katrina, high-resolution satellite imagery showed where flood waters had receded, providing valuable assistance to relief and recovery efforts. Satellite data are also being used to identify the rate of subsidence in the Mississippi Delta, including New Orleans—valuable information for use in efforts to rebuild and also to address long-term environmental challenges. Ice Sheet Decay One of the greatest risks of human-induced climate change is the possibility that some of the world’s major ice sheets, including those atop Greenland and West Antarctica, could melt partially or completely if global average tem- perature rises by as little as 3°C. These ice sheets are now being monitored from space by the Gravity Recovery and Climate Experiment (GRACE), a collaboration between NASA and the German Aerospace Center. By measur- ing tiny changes in the separation between the two GRACE spacecraft, the system generates precise maps of month-to-month changes in the gravitational pull exerted by Earth, including its major ice sheets. In 2006, scientists used GRACE data to confirm that the melting of the Greenland ice sheet had accel- erated over the last few years. Ozone Depletion In 1978, NASA satellites began to provide reliable, high-resolution maps of global ozone on a daily basis. These data proved critical in verifying and analyzing the seasonal ozone hole discovered above Antarctica in the mid-1980s. Recent mis- sions have clarified seasonal and geographic variations in ozone concentrations over Antarctica and elsewhere around the globe. Although implementation of the Montreal Protocol and its limits on chlorofluorocarbon emissions should allow the Antarctic ozone hole to heal in the next few decades, satellite monitoring of ozone remains vital. U.S. and European observations showed that the 2006 ozone hole was as large as any ever observed, with more ozone eroded (as measured by mass deficit) than in any prior year for which data were available.