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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN Executive Summary INTRODUCTION Currently, the Departments of Defense (DOD) and Commerce (DOC) acquire and operate separate polar-orbiting environmental satellite systems that collect data needed for military and civil weather forecasting. The National Performance Review (NPR)1 and subsequent Presidential Decision Directive (PDD)/NSTC-2, dated May 5, 1994, directed the DOD (Air Force) and the DOC (National Oceanic and Atmospheric Administration, NOAA) to establish a converged national weather satellite program that would meet U.S. civil and national security requirements and fulfill international obligations.2 NASA's Earth Observing System (EOS), and potentially other NASA programs, were included in the converged program to provide new remote sensing and spacecraft technologies that could improve the operational capabilities of the converged system. The program that followed, called the National Polar-orbiting Operational Environmental Satellite System (NPOESS), combined the follow-on to the DOD's Defense Meteorological Satellite Program and the DOC's Polar-orbiting Operational Environmental Satellite (POES) program. The tri-agency Integrated Program Office (IPO) for NPOESS was subsequently established to manage the acquisition and operations of the converged satellite. NASA officials have long envisioned developing operational versions of some of the advanced climate and weather monitoring instruments planned for EOS. In its 1995 EOS “Reshape” exercise, NASA adopted the assumption that some of the planned measurements in the second afternoon (PM) satellite series would be supplied by NPOESS. Although NASA has altered its earlier plans for the PM satellite and other follow-on missions to the first EOS series, its intent to integrate NPOESS into its Earth observation missions remains intact. This report, the result of the first phase of a study by the Committee on Earth Studies, analyzes issues related to the integration of EOS and NPOESS, especially as they affect research and monitoring activities related to 1 See DOC12: “Establish a Single Civilian Operational Environmental Polar Satellite Program,” in Appendix A of From Red Tape to Results: Creating a Government that Works Better and Costs Less (National Performance Review Part I). Available on the World Wide Web at <http://www.npr.gov/library/nprrpt/annrpt/redtpe93/index.html>. 2 “Fact Sheet: U.S. Polar-Orbiting Operational Environmental Satellite Systems and Convergence of U.S. Polar-Orbiting Operational Environmental Satellite Systems and Landsat Remote Sensing Strategy,” statement by the White House Press Secretary, May 10, 1994. Available on the World Wide Web at <http://www.whitehouse.gov/WH/EOP/OSTP/NSTC/html/pdd2.html>.
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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN Earth's climate and whether it is changing.3 The development of high-quality, long-term satellite-based time series suitable for detection of climate change as well as for characterization of climate-related processes poses numerous challenges. In particular, achieving NASA research aims on an NPOESS satellite designed to meet the high-priority operational needs of the civil and defense communities will require agreement on program requirements, as well as coordination of instrument development activities, launch schedules, and precursor flight activities. The study of climate processes requires a coherent, comprehensive system that carefully balances research requirements that are sometimes in conflict with operational requirements. Long-term, consistent data sets require careful calibration, reprocessing, and analysis that may not be necessary to meet the needs of short-term forecasting. Acquisition of multiple copies of a satellite sensor may be the simplest and most cost-effective means to ensure data continuity, but this strategy may preclude the insertion of new techniques to improve the observations in response to lessons learned during analysis of long data records. Such conflicts are difficult to resolve and are complicated by differences in agency cultures, charters, and financial resources. APPROACH AND OBSERVATIONS In performing its assessment, the committee reviewed eight variables (eight measurement areas) that it believed to be representative of the wide-ranging set of potential variables to be measured in a climate research and monitoring program. The committee adopted this strategy in part because there is no unique set of “climate variables,” nor is there consensus on what might constitute a minimal set of variables to be monitored in a climate research program. The committee assessed the eight variables in terms of their value to climate science and whether the present state of measurements and their associated algorithms were adequate to produce “climate-quality” data products. Included in the committee's analysis is an assessment of the role of new technology or new measurement strategies in enhancing existing climate data products or delivering new data products of interest. Common Issues In its review of the eight representative climate variables the committee identified the following common issues: Need for a comprehensive long-term strategy. Systems for observing climate-related processes must be part of a comprehensive, wide-ranging, long-term strategy. Monitoring over long time periods is essential to detecting trends such as changes in sea-surface temperature and to understanding critical processes characterized by low-frequency variability. The committee notes that an observing system developed for long-term climate observations may also very well reveal unexpected phenomena, as was the case with observations of the large-scale, low-frequency El Niño/Southern Oscillation. Desirability of multiple measurements of the same variable using different techniques. Corroborating results from a variety of observing techniques increases confidence in the data; conflicting measurements suggest problems in data quality or newly emerging science questions that must be resolved. Diversity of satellite observations and sampling strategies and support for ground-based networks. While plans for NPOESS and EOS have focused primarily on polar-orbiting satellites, satellite observations from other orbits (low inclination, geostationary) have important roles in the development of a climate observing system. Differing sampling strategies will also be needed to tailor measurement requirements to instrument capabilities in a cost-effective manner. 3 The committee's forthcoming phase two report, Issues in the Integration of Research and Operational Satellite Systems for Climate Research: II. Implementation (NRC, 2000), addresses systems engineering issues related to sensor replenishment and technology insertion, explores technical approaches to data continuity and interoperability from the standpoint of data stability, and considers issues in instrument calibration and data product validation.
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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN Ground-based networks support and extend the space-based observations. They are critical for calibrating and validating space-based measurements; they also complement space-based measurements and often provide the high-resolution measurements in both time and space needed to carry out the process studies that elucidate the mechanisms underlying climate-related phenomena. In reviewing its notional set of eight climate variables, the committee found that more attention to development of ground-based networks was warranted. Preserving the quality of data acquired in a series of measurements. A particular challenge in the design of a climate observing systems is how to preserve data quality and facilitate valid comparisons of observations that extend over a series of spacecraft. With the regular insertion of new technology driven by interest in reducing costs and/or improving performance also comes the need to separate the effects of changes in the Earth system from effects ascribable to changes and gaps in the observing system. Effective, ongoing programs of sensor calibration and validation, sensor characterization, data continuity, and strategies for ensuring overlap across successive sensors are thus essential. Data systems should be designed to meet the need for periodic reprocessing of the entire data set. The role of data analysis and reprocessing. An active, continuous program of data analysis and reprocessing adds value to existing data sets and enables the development of new algorithms and new data products. Technology development and improved measurement capabilities. New sensors are needed to reduce costs and to improve existing measurement capabilities. In addition, some climate-related variables, for example, soil moisture, cannot be measured adequately with existing capabilities. Moreover, it is not clear that all critical climate-related variables have even been identified. With improved coordination with NOAA and the IPO for NPOESS, NASA technology development efforts would better address these issues and help provide increased capabilities for the operational meteorological system. Carrying Out Climate Research from Space-Based Platforms Operational agencies generally respond to short-term demands for data products; research agencies are also under increasing pressure to respond to short-term demands for technology development and science missions that can be accomplished in a few years. As a result, political and programmatic pressures for short-term returns (both in terms of science and protection of life and property) have resulted in an operational agency focus on the acute problems of storms, earthquakes, and other severe events—even though there is growing evidence that the long-term trends associated with climate will have significant economic and social impacts. Addressing the issues associated with climate will require a long-term focus and a commitment to maintain long-term, high-quality observing systems. Climate research and monitoring require a blend of short-term, focused measurements as well as systematic, long-term measurements. While the generally shorter-term and more detailed studies that characterize process studies might appear to be in opposition to a long-term program of systematic measurements, the committee emphasizes that climate-related processes are often revealed only through the study of data from long-term systematic measurements. Achieving an appropriate balance across agencies between short-term and long-term activities related to climate research, such as a balance between process studies and monitoring activities, has proved difficult. Recent NRC studies have recommended that the Executive Branch establish an office to develop and manage a climate observing strategy.4 NPOESS and Climate Research The 1994 Presidential Directive to converge DOD and DOC meteorological programs initiated a lengthy process among Air Force and NOAA operational and research users to produce a detailed list of measurement requirements. The culmination of this effort was the Integrated Operational Requirements Document (IORD-1) 4 See, for example, NRC (1998, 1999b).
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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN that was formally endorsed by NOAA, DOD, and NASA.5 The IORD-1 consists of 61 environmental data records (EDRs) deemed necessary to the success of NPOESS. The EDRs are distributed among six categories: atmospheric parameters, cloud parameters, Earth radiation budget parameters, land parameters, ocean and water parameters, and space environmental parameters. The EDRs developed in the IORD-1 describe a well-defined, detailed set of measurements that have demonstrable value in the primary NPOESS mission of short-term weather forecasting. Climate research and modeling, however, require assimilation and analysis of a much broader set of measurements that may also be characterized by different time and space scales. Instrument stability is a key consideration in the analysis of whether climate variables are changing, yet it is undefined for many of the EDRs. Further, the IORD-1 does not set requirements on the stability or longevity of the stipulated measurements. Despite these problems, the committee believes that NPOESS offers a unique opportunity to establish a satellite-based observing system for climate research and monitoring. Although the NPOESS and NASA EOS missions as currently planned may not be optimum for climate research, many of the critical components are already in place. These include an initial commitment to data stability on the part of the NPOESS IPO, an active program of data analysis and data product validation by NASA's Earth Science Enterprise (ESE), and an active plan for NASA and NOAA collaborative missions such as the NPOESS Preparatory Project. The committee is concerned, however, that budget pressures, shifting programmatic interests, and a lack of overall vision and leadership may continue to inhibit the establishment of a coherent Earth observing system for climate research and monitoring.6 Challenges in the Integration of NASA/ESE and NOAA/NPOESS Programs Division of responsibility in the integration of research and operational missions. Climate research and monitoring raise issues that transcend the capabilities of any single federal agency. Yet, in the committee 's view, no effective structure is currently in place in the federal government that can address such multiagency issues as the balance between satellite and ground-based observations, long-term and exploratory missions, and research and operational needs. The committee concurs with recent NRC reports that have expressed concern over the lack of overall authority and accountability, the division of responsibility, and the lack of progress in achieving a long-term climate observing system.7 The challenges in integrating ESE research satellite missions and NPOESS operational satellite missions underscore these critical issues. Adequacy of NPOESS environmental data requirements for climate research. The EDR process established by the IPO supports the primary operational goals of DOD and NOAA but was not intended to yield instrument specifications that meet climate research requirements. For example, many climate research studies require access to unprocessed sensor-level data, whereas the EDR approach focuses on the final data products. In many cases, the current EDRs are not completely specified, and in some, they are not adequate for climate research. A particular issue is the absence of measurement stability and longevity specifications for many of the EDRs. Ensuring the long-term (systematic) record begun by EOS. NASA's ESE plans that certain measurements begun on EOS satellites will be integrated later into the NPOESS program. However, given the budgetary and programmatic uncertainties that have historically characterized the EOS program, there can be no assurance that this integration will be successful. Further, the committee notes that while long-term observations are essential for climate studies, NASA's new EOS plan focuses on short-term (3- to 5-year) missions. For NASA to be able to pursue a science-based strategy that leverages NPOESS capabilities where possible, the agency will probably also have to fly complementary missions and collect specialized data sets. 5 An updated IORD and other documentation related to the NPOESS program are available online at <http://npoesslib.ipo.noaa.gov/ElectLib.htm>. 6 An additional set of issues relates to the development of suitable long-term climate data archive, the subject of another study by the committee, Ensuring the Climate Record from the NPP and NPOESS Meteorological Satellites, currently in press. 7 See, for example, NRC (1998, 1999a,b).
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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN Satellite observing systems are developed for a range of objectives that sometimes conflict, leading to the need for a framework to evaluate trade-offs and to manage risk. The NPOESS Preparatory Project (NPP) under consideration by NASA and the IPO is an encouraging step toward addressing the need to maintain continuity of critical data sets between the end of the EOS platforms and the launch of the first NPOESS platforms. Development of sustainable instrumentation. Sensors developed for NASA ESE research missions are generally intended to make ambitious state-of-the-art measurements. They are typically relatively complex and often are developed in small numbers, or even as one of a kind. In contrast, sensors for operational weather forecasting missions are generally less expensive to build and operate and are designed with reliability as a key requirement. Repeat flights of identical sensors are typical in NOAA operational meteorology programs. Developing instruments appropriate for both research- and operational-type missions that can be sustained over the longer periods characteristic of a climate research program will be a particular challenge as EOS and NPOESS satellites are integrated. Prioritizing and establishing an observing strategy. The climate research community has not yet prioritized critical data sets or developed an overall national observing strategy, including algorithm development, calibration and validation, ground observations, and new technology. Climate research priorities should reflect scientific need, while recognizing technological, fiscal, and programmatic constraints. Other important aspects of such a strategy will be periodic evaluation and readjustment of specific mechanisms for transferring data sets from research to operations. Articulation of a long-term context, spanning as much as a century or more, will be paramount in developing a credible climate observing policy. RECOMMENDATIONS The following recommendations are directed to the climate research community, NASA's Earth Science Enterprise, and the NPOESS Integrated Program Office. They derive from consideration of the common issues associated with the space-based measurement of climate variables and committee concerns related to the conduct of climate research. Recommendation 1. Climate research and monitoring capabilities should be balanced with the requirements for operational weather observation and forecasting within an overall U.S. strategy for future satellite observing systems. The committee proposes the following specific actions to achieve this recommendation: The Executive Branch should establish a panel within the federal government that will assess the U.S. remote sensing programs and their ability to meet the science and policy needs for climate research and monitoring and the requirements for operational weather observation and forecasting. —The panel should be convened under the auspices of the National Science and Technology Council and draw upon input from agency representatives, climate researchers, and operational users. —The panel should convene a series of open workshops with broad participation by the remote sensing and climate research communities, and by operational users, to begin the development of a national climate observing strategy that would leverage existing satellite-based and ground-based components. Recommendation 2. The Integrated Program Office for NPOESS should give increased consideration to the use of NPOESS for climate research and monitoring. The committee proposes the following specific actions to achieve this recommendation: The IPO should consider the climate research and monitoring capabilities of NPOESS along with other NPOESS requirements. For those NPOESS measurements that are deemed to be critical for climate research and monitoring, the IPO should establish a science oversight team with specific responsibilities for each associated sensor suite. The IPO should begin to establish plans for sensor calibration and data product validation as well as for data processing and delivery that consider the needs for climate research.
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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN Recommendation 3. The NASA Earth Science Enterprise should continue to play an active role in the acquisition and analysis of systematic measurements for climate research as well as in the provision of new technology for NPOESS. The committee proposes the following specific actions to achieve this recommendation: NASA/ESE should develop specific technology programs aimed at the development of sustainable instrumentation for NPOESS. NASA/ESE should ensure that systematic measurements that are integrated into operational systemscontinue to meet science requirements. NASA/ESE should continue satellite missions for many measurements that are critical for climate research and monitoring. Recommendation 4. Joint research and operational opportunities such as the NPOESS Preparatory Project should become a permanent part of the U.S. Earth observing remote sensing strategy. The committee proposes the following specific actions to achieve this recommendation: The NPP concept should be made a permanent part of the U.S. climate observing strategy as a joint NASA-IPO activity. Some space should be reserved on the NPOESS platforms for research sensors and technology demonstrations as well as to provide adequate data downlink and ground segment capability. NPP and NPOESS resources should be developed and allocated with the full participation of the Earth science community. REFERENCES National Research Council (NRC). 1998. Overview, Global Environmental Change: Research Pathways for the Next Decade. Washington, D.C.: National Academy Press. National Research Council (NRC). 1999a. The Adequacy of Climate Observing Systems. Washington, D.C.: National Academy Press. National Research Council (NRC), Space Studies Board. 1999b. “Assessment of NASA's Plans for Post-2002 Earth Observing Missions,” short report to Dr. Ghassem Asrar, NASA's Associate Administrator for Earth Science, April 8. National Research Council, Space Studies Board. 2000. Issues in the Integration of Research and Operational Satellite Systems for Climate Research: II. Implementation. Washington, D.C.: National Academy Press, forthcoming.
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