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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN 10 Issues, Challenges, and Recommendations COMMON ISSUES The committee's review of the eight selected measurement sets in terms of their value for climate research illuminated critical issues to be addressed by an integrated satellite observing system for climate research and monitoring. Specific findings are summarized in Chapter 2, Chapter 3, Chapter 4, Chapter 5, Chapter 6, Chapter 7, Chapter 8 through Chapter 9. Here, the committee highlights the technical and programmatic issues that are common across all measurements. These include both technical issues related to the need to ensure data continuity and interoperability as well as programmatic issues related to the integration of research with operational missions. Monitoring Trends and Understanding Processes 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, as discussed in Chapter 2 with respect to the importance of trends in radiance data records, in Chapter 4 dealing with trends in land-cover change, and also in Chapter 8 concerning trends in ozone destruction. Long-term monitoring is also necessary to understand critical processes that are characterized by low-frequency variability. Process studies focusing on specific regions or issues of scientific interest are another critical element. Because changes on a wide range of time and space scales affect Earth, it is not possible to determine a priori and with certainty the types of observations that should be made and the appropriate sampling strategy. An observing system may very well reveal unexpected phenomena such as the large-scale, low-frequency El Niño/Southern Oscillation, as discussed in Chapter 3 on sea surface temperature, and scientific opportunities are lost if the observing strategy cannot adapt accordingly. Desirability of multiple measurements of the same variable using different techniques. Many of the processes of interest for climate research and monitoring can be observed using multiple techniques. If such measurements corroborate results, revealing similar patterns and trends, then confidence in the overall quality of the data increases. Similarly, if the measurements are in conflict, then this information may suggest problems in data quality or newly emerging science questions that need resolution. The advantages of multiple measurements obtained with a variety of techniques are discussed for the study of atmospheric temperature and moisture
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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN soundings (Chapter 2), sea surface temperature (Chapter 3), land cover (Chapter 4), aerosols (Chapter 7), and Earth's radiation budget (Chapter 9). Diversity of satellite observations and sampling strategies and support for ground-based networks. An effective climate observing system depends on diverse satellite observations and sampling strategies, including measurements made by ground-based networks. The measurement tools must be responsive to the requirements imposed by the variables to be observed. While NPOESS and EOS have focused primarily on polar-orbiting satellites, satellite observations from other orbits (low inclination, geostationary) are also necessary (see Chapter 2, Chapter 3, Chapter 8, and Chapter 9). Some critical sensors will be flown by international partners, and so it will be important to integrate scientific findings on a more global basis (as discussed in Chapter 1, Chapter 3, Chapter 4, Chapter 5, Chapter 7 and Chapter 8). Surface- or ground-based networks to support process studies are also required, as discussed in Chapter 4, Chapter 5, and Chapter 7; concern for the neglect of these is expressed in Chapter 4. High-resolution measurements in both time and space (as discussed in Chapter 4, Chapter 5, Chapter 6, and Chapter 7) are a critical element of many process studies. As the observing systems improve, it is likely that undersampling (in time and space) will come to dominate the errors in the system (see Chapter 1, Chapter 2, Chapter 7, and Chapter 8). Innovative strategies, such as the use of satellite constellations, may be important for some applications, as expressed in Chapter 3. Preserving the quality of data acquired in a series of measurements. It takes a special effort to preserve the quality of data acquired with different satellite systems and sensors, so that valid comparisons can be made over an entire set of observations. There are few examples of continuous data records based on satellite measurements where data quality is consistent across changes in sensors, even when copies of the sensor design are used. Sensor characterization and an effective, ongoing program of sensor calibration and validation are essential in order to separate the effects of changes in the Earth system from effects owing to changes in the observing system. Providing for overlap across successive sensors is critical, especially given the regular insertion of new technology driven by the need to reduce costs and/or improve performance. Concern about preventing data gaps, ensuring data continuity, and developing overlap strategies is expressed in Chapter 3, Chapter 4, Chapter 5, Chapter 7, Chapter 8, and Chapter 9. Data systems should be designed to meet the needs for periodic reprocessing of the entire data set. An aggressive, science-driven program to ensure long-term data quality and continuity is very important. The role of data analysis and reprocessing. Improvements in understanding will come from continued, thorough analysis of new and ongoing observations. An active program of data analysis and reprocessing will add value to existing data sets by expanding the purposes for which they can be used and will enable development of new algorithms and new data products. Such analysis will also provide the basis for investment in new technologies for needed improvements such as innovative sensors. Technology development and improved measurement capabilities. New sensors are needed to reduce costs and to improve measurement capabilities. For example, higher-resolution sensors could help resolve some of the still open questions discussed in Chapter 4, Chapter 5, and Chapter 7. Moreover, because all critical climate-related variables may not yet have been identified, and some, such as soil moisture (Chapter 6), cannot yet be measured effectively from space, continued technology and science investment is required. By coordinating its technology efforts with those of IPO/NPOESS, NASA could address these issues and help provide increased capabilities for the operational meteorological system. Status of NASA and IPO/NPOESS Integration 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. There is currently no effective structure in place in the federal government that can address such multiagency issues as the balance between satellite and ground observations, long-term and exploratory missions, and research and operational needs. The committee concurs with the several 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 (see, for example, NRC 1998a,b and 1999a,b; see also footnote 3 in Chapter 1). The challenges in integration of NASA/ESE research satellite missions and IPO/NPOESS operational satellite missions highlight the critical issues.
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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN Adequacy of NPOESS environmental data records for climate research. The current emphasis by IPO/NPOESS on environmental data records does not ensure development of a system that will meet the requirements for climate research. The EDR process established by IPO/NPOESS supports the primary operational needs of DOD and NOAA but was not intended to yield instrument specifications that meet climate research requirements (see Chapter 1, Chapter 4, Chapter 5, Chapter 7, and Chapter 8. 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 because they do not, for example, specify measurement stability and longevity (see Chapter 4, Chapter 5, Chapter 7, and Chapter 8). The NASA/ESE approach to long-term measurements. The current NASA/ESE approach relies on a strategy of systematic measurements that may be integrated into NPOESS with no assurances that this integration will be successful. Long-term observations are essential for climate studies, yet 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 to collect some specialized data sets (see Chapter 1 for a discussion of NASA's and NOAA's approaches to long-term measurements). A systemwide analysis of research and operational requirements is not currently in place. Such an analysis is necessary to ensure that scientific and programmatic requirements are met on a continuing basis. The NPOESS Preparatory Project is an encouraging step in 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. However, there is no assurance that the NPP experience will be repeated for other important data sets. For example, the NPOESS IPO is planning to derive vector winds from passive microwave data; however, launch of the planned Navy Windsat satellite may be necessary to prove the technique. Moreover, there is no assurance that the Navy will continue the Windsat program, and NASA support for follow-ons to its scatterometers is also not assured. Development of sustainable instrumentation. There is no indication, at present, that as measurement capabilities are integrated, the development of sustainable instrumentation will receive the necessary attention. Research instruments often are complex and are intended to make ambitious state-of-the-art measurements. Operational sensors generally should be less expensive to build and operate and above all else must be reliable, requirements that should be balanced with those for climate research, coupled with appropriate stability and longevity requirements. 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, sensor calibration and validation, ground observations, and new technology. 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. Without such a commitment, a climate observing policy will be meaningless. THE CHALLENGES OF SPACE-BASED CLIMATE RESEARCH There are many challenges associated with 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. In addition to addressing technical issues, satellite-based climate observing strategies must take into account conflicting requirements and differing agency cultures. These well-known structural problems and issues are not unique to satellite missions; similar problems confront ground-based climate observing strategies (NRC, 1999a). Nevertheless, despite such challenges, there is now an opportunity to make progress toward developing satellite-based observing systems that, while not optimum, will support climate research. Climate research and monitoring require a blend of short-term, focused measurements as well as systematic, long-term measurements (see Chapter 1). Various problems have precipitated an impasse that inhibits researchers ' ability to study and monitor
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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN climate change from either satellites or in situ systems. Measurements often are not made with sufficient accuracy or precision (see Chapter 2, Chapter 3, and Chapter 8), changes in instrumentation lead to inconsistent data records, and the records are sporadic. Data archives are not designed to facilitate large-scale reprocessing of data, and pricing policies discourage large-volume data extraction. The political and programmatic pressures for short-term returns (both in terms of science and protection of life and property) lead to short changing of the chronic problems of climate change and climate variability in favor of the acute problems of storms, earthquakes, and other severe events.1 Current federal divisions of responsibility constitute a structural impediment to the integration of operational and research components for Earth observation. Overcoming these structural obstacles will require the initiative of the Executive Branch of the federal government to build a broad consensus and then assign clear responsibilities and authority. The outcome of this effort would be a strategy that balances the interests and needs of various constituencies. Key stakeholders include not only the climate research community and the operational agencies, but also the broader Earth science community and other public and private entities that stand to benefit from a strong national program of Earth observations and research. These diverse stakeholders need to be brought together to achieve goals that transcend those of the individual entities. Reaching agreement on how to resolve issues will require compromise and collaboration, rather than mandates. There is, at present, no effective forum within the government for making trade-offs and weighing options with regard to short-term forecasting systems for operational needs, long-term, systematic observing systems, and process studies needed for climate research. Research agencies such as NASA are wary of any commitment to maintaining long-term operational satellite monitoring systems that may prevent them from pursuing new technologies and new research directions. Operational agencies such as NOAA and DOD are wary of committing to long-term observation requirements that may impose significant new costs on an already-cost-constrained system. The Earth science community, while recognizing the need for long-term observations for some climate processes, is wary of relinquishing responsibility for and oversight of instrumentation to an operational agency that may find an “instrument facility” approach necessary to manage multiple demands and the long-term stability and performance of the sensor system. Achieving progress will require the initiative of the federal government, with active planning and continuing involvement by the climate research community. Various agency configurations have been proposed as solutions to this dilemma. For example, the climate-observing mandate might be given to an operational agency such as NOAA. At the very least, NRC panels have suggested that the Executive Branch establish an office to manage a climate observing system (NRC, 1998a, 1999b). However, climate research and monitoring require a culture and a program structure far different from those currently in place in NOAA. Moreover, there is still a strong research component that must be maintained; the collection of many climate measurements is simply not ready to be placed under operational control, and new measurements and technologies aimed at augmenting or improving the operational measurement suite ought to continue to be developed. An alternative plan would be to engage the National Science and Technology Council, which could balance the operational elements of NOAA and the IPO with the research elements of NASA. However, the potential scientific and programmatic consequences of any of these possible options have not been studied in detail. Although the key agencies are beginning to propose studies, the committee is concerned that the eventual solution will be based largely on programmatic and fiscal constraints, not on the needs identified for climate research and monitoring. Maintaining the status quo will continue to impede progress in understanding the processes of climate change and variability. Without such understanding, researchers will be unable to deliver sound scientific information and advice to policymakers to support informed decision making. Over the past 20 years, the power of satellite remote sensing to illuminate global-scale processes, especially in the area of short-term predictions, has become clear. 1 However, there is growing evidence that long-term trends associated with climate will have significant economic impacts. For example, if the frequency of hurricanes on the U.S. East Coast changes, then the property insurance industry will have to adjust its investment and pricing policies. Similarly, long-term changes in precipitation in the Pacific Northwest may force the timber industry to alter its cutting cycle.
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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN However, progress toward a climate observing system remains problematic. The IPO has recognized the requirements for climate observations through its inclusion of stability requirements for certain variables. The longer design life for the NPOESS sensors is also helpful. Nevertheless, the IPO has no mandate for climate observation. NASA/ESE has recognized the need to coordinate more closely with operational programs such as NPOESS to ensure long-term systematic measurements for critical climate variables. Activities such as the NPOESS Preparatory Project are tangible examples of such cooperation. However, from the perspective of the climate research community, much remains to be done. The overall integration of both operational and research components needs to be actively managed so that there is an effective process to achieve regular rebalancing in light of technological and scientific advances. NPOESS offers a unique opportunity to establish a satellite-based climate observing system. 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, 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 lack of overall vision and leadership may continue to inhibit the establishment of a coherent Earth observing system for climate research and monitoring. RECOMMENDATIONS The following recommendations 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. They are directed to the climate research community, the NASA Earth Science Enterprise, and the NPOESS Integrated Program Office. 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. NPOESS represents a significant step forward in the nation's ability to produce and deliver short-term observations and predictions on Earth processes for protection of life and property. The present U.S. remote sensing strategy also contains many of the critical elements necessary for climate research and monitoring. Executive level initiative is essential to reconcile these requirements and to ensure that the nation's needs for short-term predictions are balanced with the needs to deliver scientifically based information on longer-term climate processes. Although the NPOESS platforms represent an essential component for stable, long-term observations, the present approach does not ensure that climate research needs will be met. Coordination of the needs for systematic and process measurements, sustainable and innovative technology, satellite and ground-based observations, and rapid delivery of data as well as ongoing, creation of long-term, consistent data sets relies primarily on a set of ad hoc agreements. A rigorous plan is needed, within the constraints of resources and assets, for achieving a rational balance between short-term (weather) and longer-term (climate) objectives. This balance should be evaluated on a periodic basis as scientific, programmatic, and fiscal constraints change. 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 the requirements for operational weather observation and forecasting. Such a panel would monitor agency efforts to provide balanced consideration of operational and climate research requirements. Elements to be considered include the research missions undertaken by NASA/ESE, the operational missions of IPO and NOAA, as well as ground-based networks and associated data systems. Remote sensing missions to be considered include polar, low inclination, and geostationary orbits. The panel should meet
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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN on a regular basis to assess the evolution of climate research and technological capabilities and to recommend adjustments to the observing system where appropriate. 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 would maintain cognizance of all the critical elements of the observing system that are relevant to operational uses and to climate research. It would pay close attention to the overall U.S. strategy to meet both sets of requirements, within the constraints imposed by schedule, funding, technology, and programmatics. It would recognize that there is not an “optimum” system but ensure that climate research requirements are considered along with other requirements. 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. The workshop process would establish the science priorities for climate observations and contribute to the development of a strategy that best meets these priorities within fiscal, schedule, technical, and programmatic constraints. Particular attention should be paid to the emerging plans of NASA/ESE, leveraging these with the capabilities of IPO/NPOESS programs. Although the initial focus would be on NASA and IPO, attention should also be paid to the other national and international components of the observing system as well as to modeling, data analysis, and algorithm development. Recommendation 2. The Integrated Program Office for NPOESS should give increased consideration to the use of NPOESS for climate research and monitoring. The development of NPOESS should greatly improve short-term observations and predictions. Because of its emerging commitment to data stability, long-life platforms, and more capable sensors, there is an opportunity to develop NPOESS as part of the U.S. climate observing strategy without jeopardizing its focus on operational short-term forecasts. 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. The proposed panel on satellite-based measurements for climate research should review and provide advice to the IPO as its plans for NPOESS mature, including its overall plans for sensor characterization, algorithm development, product validation, data system design, and so on. However, this approach should not be construed to mean that NPOESS should become a climate research mission, but rather that climate research requirements will be considered along with other 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. Because climate research requires the close involvement of scientists in all aspects of sensor development and operations, the IPO should establish mechanisms that go beyond the traditional contractor-selected teams. Climate science teams should be selected through a competitive process, perhaps in coordination with NASA. These science teams would function much like a NASA science team, developing and documenting algorithms, validating data products, and so on, but would focus on climate research. 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. Although the NPOESS sensors will not be launched for several years, climate research and monitoring will impose unique requirements on data systems and data quality. By utilizing the capabilities of NASA (where feasible), it may be possible to meet these requirements at a reduced cost to the IPO. Since NPOESS sensor development will begin soon, such efforts should start now to ensure that proper sensor tests are designed and implemented and critical information on sensor performance is maintained.
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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. Through its funding of climate research and its investments in technology, NASA can significantly enhance the climate research and monitoring capabilities of NPOESS and other operational missions. Activities could include the flight of complementary sensors and support for sensor characterization, as well as sensor calibration and data product validation, research and analysis, data reprocessing, and development of new technology. 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. Operational missions have stringent cost (for both development and operations) and longevity requirements, whereas the development of research instrumentation often faces fewer such constraints (especially in the short-term technology-driven missions in NASA/ESE's Earth Probes program). This discrepancy inhibits commitment by an operational agency to incorporate new technology into its programs. NASA should allocate some of its technology investments specifically to incentives designed to encourage the transition of technology to operational status, such as lowering the costs and improving the reliability and performance of candidate sensors. This might also include innovative methods for ensuring data continuity and sensor calibration. Such an approach can work effectively only if NASA's ESE and the NPOESS IPO cooperate at all stages of the process. NASA/ESE should ensure that systematic measurements that are integrated into operational systems continue to meet science requirements. Although NASA/ESE intends to shift long-term responsibility for systematic measurements to operational programs, this may require that NASA/ESE continue to allocate resources to these measurements. Operational measurements may need enhanced capability, sensors may require more extensive calibration, and data will need to be analyzed and reprocessed. Operational programs may provide stable orbiting platforms, but not necessarily all of the infrastructure required to accomplish climate research and monitoring. NASA/ESE should continue satellite missions for many measurements that are critical for climate research and monitoring. Because of conflicting requirements, some of the measurements required for climate research may not be incorporated into operational programs such as NPOESS. For example, some may not be deemed critical for short-term forecasts, or they may simply be too costly. NASA/ESE should continue such critical measurements, while pursuing new technologies or approaches that may reduce the costs of such observations. It is unrealistic to expect that all of NASA/ESE's systematic measurement requirements can be met by NPOESS. Recommendation 4. Joint research and operational opportunities such as the NPOESS Preparatory Project (NPP) should become a permanent part of the U.S. Earth observing remote sensing strategy. The Operational Satellite Improvement Program (OSIP) was a joint activity between NASA and NOAA to improve short-term weather forecasting. A similar program in the area of climate research could help to fill the serious gap that now exists between the NASA/ESE research missions and the operational missions such as NPOESS. Operational missions tend to be conservative, valuing highly reliable and proven sensor designs as well as sensors that are inexpensive to operate. Research missions often value cutting-edge technology and favor new designs and new scientific approaches. A joint program could buffer the rapidly changing mix of science and technology emerging from NASA with the more constant requirements and capabilities of operational programs. 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. A permanent R&D testbed evolved from NPP would provide a unique opportunity to infuse research requirements and innovative technology into NPOESS without disrupting the operational requirements. In much the way that Nimbus provided a regular series of satellite platforms, a permanent series of NPP-style platforms could fly
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ISSUES IN THE INTEGRATION OF RESEARCH AND OPERATIONAL SATELLITE SYSTEMS FOR CLIMATE RESEARCH: I. SCIENCE AND DESIGN both operational and candidate operational sensors that measure identical variables as well as test new sensor concepts. A permanent NPP would ease the integration of research and operational missions by reducing risk and increasing confidence. 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. Current NPOESS plans include limited spare satellite resources (space, weight, power, etc.) that could support flight demonstrations of new sensor concepts. These resources are needed to ensure continued evolution of NPOESS capabilities over the decades that it will be in operation. Such an approach is only prudent and will ensure that NPOESS continues its state-of-the-art capabilities in short-term forecasting as well as improving its capabilities for climate research. NPP and NPOESS resources should be developed and allocated with the full participation of the Earth science community. Because of time limitations, current plans for NPP were developed without much input from the science community. If the NPP concept is to be a permanent program element, then it is essential that future implementations be developed with much broader participation. Long-term goals should also be established. Some of the spare resources on the NPOESS platforms should be allocated based on a competitive process to ensure that the best science is accomplished. Such a program could be administered jointly by NASA and IPO as joint research announcements. REFERENCES National Research Council (NRC). 1995. Earth Observations from Space: History, Promise, and Reality. Washington, D.C.: National Academy Press. National Research Council (NRC). 1998a. Overview, Global Environmental Change: Research Pathways for the Next Decade. Washington, D.C.: National Academy Press. National Research Council (NRC). 1998b. The Atmospheric Sciences: Entering the Twenty-First Century. 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.
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