6
Support for the Precise Geodetic Infrastructure

In previous chapters, this report outlined how components of the precise geodetic infrastructure interlock to support not only Earth science but also a wide range of applications of benefit to society. Foremost among the benefits is the realization of the International Terrestrial Reference Frame (ITRF), which is determined through the integration of the Very Long Baseline Interferometery (VLBI), Satellite Laser Ranging (SLR), Global Navigation Satellite System/Global Positioning System (GNSS/GPS), and Doppler Orbitography Radiopositioning Integrated by Satellite (DORIS) networks. The ITRF, in turn, provides the foundation for nearly all ground-based and space-based observations in Earth system science and supports a variety of applications, such as land surveying, floodplain mapping, navigation, precision agriculture, and location-based services. As emphasized in Chapter 3, the primary challenge driving advances in geodesy is the study of long-term Earth system processes, such as tectonic deformation, and indicators of global climate change, including sea-level rise and ice sheet melting. While these processes are often imperceptibly slow, they are singularly important to society and simply could not be monitored and understood without the exquisitely precise observations acquired through global geodetic networks. Despite these many applications and its scientific value, many policy makers and members of the general public seem largely unaware of the nation’s reliance on the geodetic infrastructure (with the notable exception of GPS) and are therefore reluctant to invest in its maintenance and modernization.

In the United States, geodetic activities are conducted and supported under the aegis of a range of federal science agencies with participation by the national and international academic community. The committee asked representatives of these agencies and the academic community to offer their impressions of the nation’s geodetic infrastructure in terms of strengths, weaknesses, opportunities, and threats (Box 6.1). This informal analysis provided a useful framework to address the sustainability of the nation’s geodetic infrastructure. The primary conclusion of this analysis is that the geodetic infrastructure has become increasingly fragile as a consequence of delayed replacement of aging components, lack of redundancy with single-point-of-failure designs, imperfect collaboration among contributors, reductions in the trained geodetic workforce due to retirements, and ongoing tightening of operations and maintenance budgets. These factors combined pose a risk of a sudden, drastic loss of geodetic observing capability (see also NRC, 2007c).



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6 Support for the Precise Geodetic Infrastructure In previous chapters, this report outlined how components of the precise geodetic infrastructure interlock to support not only Earth science but also a wide range of applications of benefit to soci - ety. Foremost among the benefits is the realization of the International Terrestrial Reference Frame (ITRF), which is determined through the integration of the Very Long Baseline Interferometery (VLBI), Satellite Laser Ranging (SLR), Global Navigation Satellite System/Global Positioning System (GNSS/GPS), and Doppler Orbitography Radiopositioning Integrated by Satellite (DORIS) networks. The ITRF, in turn, provides the foundation for nearly all ground-based and space-based observations in Earth system science and supports a variety of applications, such as land surveying, floodplain mapping, navigation, precision agriculture, and location-based services. As emphasized in Chapter 3, the primary challenge driving advances in geodesy is the study of long-term Earth system processes, such as tectonic deformation, and indicators of global climate change, includ - ing sea-level rise and ice sheet melting. While these processes are often imperceptibly slow, they are singularly important to society and simply could not be monitored and understood without the exquisitely precise observations acquired through global geodetic networks. Despite these many applications and its scientific value, many policy makers and members of the general public seem largely unaware of the nation’s reliance on the geodetic infrastructure (with the notable exception of GPS) and are therefore reluctant to invest in its maintenance and modernization. In the United States, geodetic activities are conducted and supported under the aegis of a range of federal science agencies with participation by the national and international academic community. The committee asked representatives of these agencies and the academic community to offer their impressions of the nation’s geodetic infrastructure in terms of strengths, weaknesses, opportunities, and threats (Box 6.1). This informal analysis provided a useful framework to address the sustain - ability of the nation’s geodetic infrastructure. The primary conclusion of this analysis is that the geodetic infrastructure has become increasingly fragile as a consequence of delayed replacement of aging components, lack of redundancy with single-point-of-failure designs, imperfect collaboration among contributors, reductions in the trained geodetic workforce due to retirements, and ongoing tightening of operations and maintenance budgets. These factors combined pose a risk of a sudden, drastic loss of geodetic observing capability (see also NRC, 2007c). 101

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10 PRECiSE GEODETiC iNFRASTRuCTuRE BOX 6.1 Informal analysis of strengths, weaknesses, opportunities, and threats of the geodetic infrastructure, as perceived by U.S. agencies Strengths Weaknesses • Collaborative initiatives involving multiple agen- • Lack of clear chain of responsibility and authority cies and countries. for maintenance and development of the nation’s • Open and transparent data collection, process- geodetic infrastructure. • Degradation and loss of geodetic stations and ing, and distribution. • Ongoing progress and improved performance satellites. • Uneven geographic distribution and inadequate over multiple decades. • Major technological advances. co-location of geodetic techniques. • Collection of accurate global position, satellite • Lack of satellite data continuity, especially for orbit, altimetry, and gravity data sets to support GRACE and IceSAT missions. • Systematic technique errors, requiring improve- research on changes in the Earth system. • Support of a broad range of groundbreaking ments in technology. • Inaccessibility of geodetic concepts and societal applications. terminology. Opportunities Threats • Continued scientific and technological advance- • Lack of general awareness and understanding of ment. contributions of geodesy. • Evolution toward geodetic imaging and real-time • Lack of sustainable, long-term funding due to applications. competing priorities and structure of the federal • Efficient data transfer from remote stations to cen- budget process. • Perception that current geodetic infrastructure is tral data processing centers, allowing for shorter time intervals and near-real-time solutions. precise enough. • Retiring workforce and lack of adequate training for the next generation of geodesists. Based on its review of prior studies and the scientific literature as well as interviews with members of stakeholder communities, the committee developed a set of recommendations for the maintenance and long-term sustainability of the geodetic infrastructure servicing the full range of existing and future users.1 These recommendations touch on the national and global fundamental station network,2 high-precision, real-time GNSS/GPS networks, international collaboration and cooperation, education of the geodetic science workforce, and long-term support of federal geodetic services. These specific recommendations, discussed in the rest of this chapter, all derive from the committee’s core recommendation: Recommendation: The united States, to maintain leadership in industry and science, and as a matter of national security, should invest in maintaining and improving the geodetic infrastructure through upgrades in network design and construction, modernization of current observing systems, deployment of improved multi-technique observing capabili - ties, and funding opportunities for research, analysis, and education in global geodesy. 1The committee developed no specific recommendation for the proposed GRAV-D project to define a gravity-based verti - cal datum for the United States, since that proposal is already official policy for NGS and is included in its 10-year plan. However, the committee endorses this concept and notes that it will be an important improvement to the existing national geodetic infrastructure. 2A fundamental station includes VLBI and SLR, plus other geodetic systems. See Glossary for full description.

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10 SuPPORT FOR ThE PRECiSE GEODETiC iNFRASTRuCTuRE THE GEODETIC INFRASTRuCTuRE AND SOCIETy Implicitly or explicitly, nearly all observations of the Earth system and applications derived from those observations depend on the geodetic infrastructure. This report illustrates that the geo - detic infrastructure is critical to the ability to understand and respond to such global issues as climate change and natural hazards, and that its impact also permeates our everyday lives. For example, drivers of cars, airplanes, and boats can now use inexpensive GPS receivers to determine their posi - tion to sub-meter precision in real time anywhere on the planet. In the foreseeable future, not only will we be able to know a vehicle’s position to centimeter accuracy in real time, but we also may be able to control that position through autonomous navigation systems. Such systems would make possible many tasks offering enormous economic advantages. In addition, future applications of precise geodesy to soil moisture mapping, precise agriculture, transportation systems, and hazard mitigation would have direct economic benefits. These current and future applications illustrate that the geodetic infrastructure and its related data sets are public goods, in the same sense that national highway systems or weather-prediction services are public goods. Previous National Research Council reports have made the case that raw environ- mental data are a public good and, as such, should be supported by taxpayers (NRC, 2001). Based on this premise, government agencies have historically covered the costs of building and operating the ground-based networks, observation satellites, and data systems that collect global environmental observations and make them available to researchers and to the public. The long-term support of geodetic equipment, data collection, and data analysis and distribution systems is, in a very direct way, a governmental responsibility that must be incorporated in the permanent mission statements and budgets of relevant state and federal agencies. In addition, because technological progress often arises from research conducted at universities and agencies that are free of any such long-term responsibil - ity, there is a need to systematically transfer technology and expertise gained from geodesy research developments to operational agencies. These agencies must in turn allocate adequate resources and prepare a workforce to take advantage of the geodetic infrastructure and support advanced applications. This is especially true of anticipated future advances, such as those described in Chapter 4. Geodetic capabilities have advanced by about one order of magnitude per decade since the first satellite operations. This rate of progress shows that a level of performance that is “pushing the envelope” today stands a good chance of becoming tomorrow’s basic requirement. As discussed in Chapters 2 and 3, many aspects of geodetic techniques, technologies, and data analysis are progress - ing rapidly today; such trends will likely persist in the foreseeable future. For example, societal applications of geodetic imaging, using active remote sensing tools such as radar and LiDAR with increasing spatial and temporal resolution and improving accuracy, will probably contribute power- fully to this progress. Recognizing the benefits of the geodetic infrastructure to science and society and considering anticipated future needs and advances, the committee developed both short-term and long-term recommendations, which are discussed in the following sections. THE NATIONAL AND GLOBAL FuNDAMENTAL STATION NETWORK Chapter 5 illustrates the critical contribution of VLBI and SLR to the determination of the ITRF. VLBI uniquely defines the orientation of the ITRF in space, while SLR provides the precise tie to the origin of the Earth (the geocenter). Together, these techniques provide the only strong constraint on the ITRF “scale,” but both are susceptible to various error sources that need to be controlled. Maintenance of these techniques, therefore, is essential for maintaining the ITRF in order to meet the ever-increasing accuracy demands of current and future geodetic applications. The most effective use of U.S. investments in this equipment, in the context of the global network, would be to upgrade current VLBI and SLR sites that have been occupied for decades, thereby retaining

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10 PRECiSE GEODETiC iNFRASTRuCTuRE and extending their worth for long-term ITRF determination. An analysis by Pavlis and colleagues (2010) demonstrated that a densification of the global network of combined VLBI and SLR stations from 8 up to 24 stations would yield substantial improvements in the ITRF. Recommendation: In the near term, the united States should construct and deploy the next generation of automated high-repetition rate SLR tracking systems at the four current u.S. tracking sites: Haleakala, Hawaii; Monument Peak, California; Fort Davis, Texas; and Greenbelt, Maryland. It also should install the next-generation VLBI systems at the four u.S. VLBI sites: Greenbelt, Maryland; Fairbanks, Alaska; Kokee Park, Hawaii; and Fort Davis, Texas. Maintaining the long history of data provided by these sites is essential for reference frame stability as we transition between ever-evolving geodetic techniques. Recommendation: In the long term, the united States should deploy additional stations to complement and increase the density of the international geodetic network in a coop - erative effort with its international partners, with a goal of reaching a global geodetic network of at least 24 fundamental stations. Other countries have recognized the importance of contributing to the global geodetic infra - structure to support the Global Geodetic Observing System initiative, as well as to advance their own national geodetic goals. One example is the AuScope project, funded under Australia’s National Collaborative Research Infrastructure Strategy (Coleman et al., 2008). With an investment of $20 million, the project plans a significant increase in Australia’s geodetic infrastructure, including three new VLBI telescopes, a VLBI correlator center, four new gravity instruments (including an absolute gravimeter), an upgrade to one of Australia’s two SLR stations, a transportable SLR campaign, and approximately 100 new continuously operating GNSS sites (Johnston and Morgan, 2010). The next generation of fundamental geodetic sites, comprising VLBI, SLR, and other geodetic systems, needs to be designed with several considerations in mind in order to satisfy requirements for ITRF accuracy and stability. All components must be accurately surveyed to provide local ties between techniques. Furthermore, NRC (1991) and Plag and Pearlman (2009) suggest that three or more GNSS/GPS stations be deployed with permanent, stable monuments within 100–1,000 meters of the SLR and VLBI sites so that differences in local site motions are either negligible or easily monitored. Co-locating three GNSS/GPS stations (or more) allows occasional updates of equipment without jeopardizing the continuity of observations. Periodic satellite or airborne InSAR site char- acterization also would be extremely valuable to ensure that local motions or deformation are well mapped and understood. These considerations are consistent with the International Association of Geodesy’s recommendation 4.1, which asks that “the ITRF be maintained and made accessible with an operational core ensuring ITRF with the accuracy, long-term stability, and the level of accessibil - ity required by Spatial Data Infrastructure applications” (Plag and Pearlman, 2009). 3 However, Plag and Pearlman (2009) urge a much expanded network—of 40 fundamental stations—by 2020. In addition, the committee also recognizes the importance of accurate gravity field measurements in support of space-based positioning techniques. Further, the proposed implementation of a national geoid-based4 height system, consistent with global gravity models and accurate to 1–2 centimeters, 3See also The GGOS 2020 Recommendations: http://www.iag-ggos.org/activities/ggos2020_recommendations.php. Ac - cessed June 3, 2010. 4The geoid is the level surface (a surface of constant gravitational potential) that approximates mean sea level. The height above the geoid is used to define the actual elevation of a point on the land surface. Extending the geoid to land was typically accomplished with ground-based leveling techniques but is now augmented with global gravity field models from space- based techniques. The International Association of Geodesy is initiating a pilot project for the definition and implementation of a unified geoid-based World Height System, but this issue, still under discussion, lies beyond the scope of this report.

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10 SuPPORT FOR ThE PRECiSE GEODETiC iNFRASTRuCTuRE requires strong support for gravity satellite missions and a revitalized U.S. terrestrial (ground and airborne) gravity program. Such a program also would support the multiple scientific and civil appli - cations that call for monitoring changes in the gravity field over regional and global scales. NATIONAL HIGH-PRECISION, REAL-TIME GNSS/GPS NETWORKS Chapters 2 and 3 of this report discuss various scientific applications that require high-preci - sion, real-time GNSS/GPS networks. The report also identifies new and future applications of societal importance that call for a rapidly sampled (at least one hertz), real-time GNSS/GPS data stream. These include systems that enable autonomous navigation for land, sea, and air vehicles and robotic equipment; precision tracking of aircraft for laser and radar imaging; monitoring of space weather in the ionosphere; early warning for such natural hazards as earthquakes and tsunamis; improved forecasting of extreme weather events; measurement of ground displacement in landslides; and monitoring of critical structures after a natural disaster to inform emergency response efforts. The Plate Boundary Observatory (PBO) GPS network, a major component of the NSF-led EarthScope program, could serve as the backbone for a national high-precision, real-time GNSS/ GPS network. This 1,100-station network, built with uniform high-quality equipment, standards, and monuments, represents a large capital investment. The potential to transition this infrastructure from research to operations at the completion of the EarthScope project presents a unique opportunity for the nation. With long-term maintenance, densification, and upgrades to facilitate tracking of other navigation satellite constellations, the PBO network would serve the dual purposes of providing both a national backbone for high-precision applications and local reference stations for surveyors and local commercial and governmental service providers. While there is an overlap between the PBO and other geodetic networks (for example, CORS and state networks), most such networks were not built specifically to support precise geodesy, and the lack of deep anchors tying the GNSS/GPS receiver to the ground in these other systems may introduce uncontrolled movements of the receiver relative to the reference system as a result of shallow deformations or temperature effects (see Agnew, 2007). Any GNSS/GPS network built to scientific standards, however, could be joined with the PBO network. One example is the approximately 200-station GPS network operated by the U.S. Geological Survey to moni - tor seismic and volcanic hazards in the western United States. Present-generation high-quality GNSS/GPS receivers in this and other networks are capable of high-rate sampling and streaming data over the Internet; consequently, many of these sites either already operate in real-time or could be upgraded to do so. The strategies for densification of a national high-precision, real-time GNSS/GPS network could be responsive to the needs of specific applications. For example, early warning systems for earth- quakes and tsunamis would require a more dense station spacing (approximately 20 kilometers apart) along the west coast of the United States. Weather prediction, on the other hand, might only require 50-kilometer spacing but would require expansion offshore to help predict the strength and tracks of hurricanes. In addition to such applications, a national high-precision, real-time network also would meet the needs of scientists conducting long-term research studies. Shared use of a single network with common transmission of data and data archiving would yield significant cost savings. Recommendation: The united States should establish and maintain a high-precision GNSS/GPS national network constructed to scientific specifications, capable of streaming high-rate data in real-time. All GNSS/GPS data from this network should be available in real-time without restrictions (and at no cost or a cost not exceeding the marginal cost of distribution), as well as in archived data files.

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10 PRECiSE GEODETiC iNFRASTRuCTuRE INTERNATIONAL COLLABORATION AND COOPERATION Chapter 4 of this report describes voluntary international collaborations, such as the Interna - tional GNSS Service (IGS), which set standards for participation, including those for site documen - tation and data provenance; oversee data analysis and quality control through analysis centers; and make data and data products freely available to users. From a global viewpoint, data from the IGS supports the GNSS/GPS component of the ITRF by enabling high-accuracy satellite orbit deter- mination and clock calibration. As such, IGS products are a natural starting point for applications requiring the highest accuracies and are routinely used by researchers and by U.S. federal agencies, even by agencies with their own “in house” capabilities (such as the U.S. Naval Observatory and the National Geospatial-Intelligence Agency). For this reason, among others, IGS is a critical asset to the United States’ geodetic infrastructure for science and commerce. In addition, its importance as an adjunct to the national high-precision GPS network recommended above cannot be overstated. A well-distributed geodetic network around the globe leads to higher accuracy and reduces dependence on data from particular stations. Poor geographic coverage leads to lower accuracy and greater dependence on particular sites, which are given undue weight in the solutions. If such stations experience temporary equipment failures, the determination of orbit parameters and the realization of the ITRF can be affected excessively, a problem that is exacerbated by the existence of systematic model errors that become more detrimental as we push to achieve greater accuracies. Stations currently in the IGS network are sparsely distributed in the southern hemisphere relative to the northern hemisphere (see Figure 5.1). To balance the data from stations in the IGS network for the purpose of maintaining the ITRF, it is therefore necessary to select an optimal subset of northern stations while depending heavily on data from all available sites located south of the equator. Consequently, maintaining and upgrading the IGS stations of the southern hemisphere and expanding the southern portion of the network to the extent possible should receive the highest priority by the IGS. NASA currently supports the United States’ contribution to the IGS network, which includes approximately 70 GPS stations both within and outside of U.S. borders. Outside the United States, some of these sites are on U.S. military bases or scientific installations, and some are operated cooperatively with local agencies or universities. Those sites that are co-located with other geodetic systems play a particularly important role in determination of the ITRF. A significant number of these co-located stations are in the southern hemisphere or other areas where the IGS network has poor geographic coverage or is otherwise weak. As a result, eliminating these stations would have unfortunate consequences for the IGS and its contribution to the ITRF. Given the geographic and temporal gaps in coverage, degrading infrastructure, and potential loss of data continuity for key geodetic observing systems, and given the increased leverage of col - laboratively funded efforts, it is in the interest of the United States to make a long-term commitment to a strong IGS network. This commitment includes support for operation and maintenance of a global network of homogeneous, high-quality sites supporting IGS standards within and outside the United States. These sites should be capable of real-time data transmission to support the recom - mended national GPS network. In addition to strengthening the global GPS network to enhance the United States’ own geo - detic infrastructure, playing a leading role in the IGS enables the United States to exert a strong and lasting influence on IGS standards and practices for the global network and IGS products. To sustain this influence, participation by United States investigators in the bureaus, analysis centers, working groups, and projects of the IGS must be supported.

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10 SuPPORT FOR ThE PRECiSE GEODETiC iNFRASTRuCTuRE Recommendation: The united States should continue to participate in and support the activities of the international geodetic services (IGS, ILRS, IVS, IDS, IGFS and IERS) by providing long-term support for the operation of geodetic stations around the world and by supporting the participation of u.S. investigators in the activities of these services. From the beginning of the field of geodesy, U.S. scientists have recognized the benefits of a global infrastructure and the need for international collaboration. Indeed, the spectacular progress in geodesy over the past half century has benefited greatly from the initial and continued U.S. lead - ership. Scientists and engineers from many nations now contribute to geodesy to the extent that no individual national contribution—including that of the United States—can be withdrawn without a visible impact. U.S. participation in international coordinating organizations has served the national geodetic community well by creating opportunities for leadership and global collaborations. The United States’ utilization of a robust global geodetic infrastructure directly benefits numer- ous commercial, military, and scientific applications. Sustaining U.S. participation in international coordinating organizations is therefore important, even from a narrowly national point of view, because the infrastructure supported by these organizations supports a wide range of domestic uses and applications. Much of the success of international collaborations relies on the commitment of volunteer participants, typically scientists and engineers, with support from governments. Although this system has served the scientific community and the general public well, there remains a per- sistent danger that competing priorities could pose a risk to the continued global operation of the geodetic infrastructure. Specifically, a long-term national commitment to the primary global geodetic product—the ITRF—would by de facto imply a long-term commitment to the geodetic infrastructure, which is needed to ensure the continuity and stability of the ITRF and the many geodetic observing systems that depend on it. Recommendation: The united States, through the relevant federal agencies, should make a long-term commitment to maintain the International Terrestrial Reference Frame (ITRF) to ensure its continuity and stability. This commitment would provide a founda - tion for Earth system science, studies of global change, and a variety of societal and commercial applications. The committee also endorses the Global Geodetic Observing System (GGOS), a component of the Global Earth Observation System of Systems (GEOSS), being built under the aegis of the Group on Earth Observations (GEO), a voluntary partnership of governments and international organiza - tions of which the United States is a leading member. GGOS links together existing and planned observing systems around the world and promotes common technical standards so that data from all these systems can be combined into coherent data sets. GGOS was conceived and introduced by the International Association of Geodesy as the new paradigm for sustained international coopera - tion toward integrating space-based geodetic techniques. The maintenance and development of the global precision geodetic infrastructure is recognized by GEO as a cross-cutting activity that affects many aspects of Earth science and the lives of most inhabitants of the planet. AN EDuCATED GEODETIC SCIENCE WORKFORCE The committee found that one of the “weakest links” in the implementation of a precision geodetic infrastructure was a lack of trained workforce to develop and maintain the infrastructure in the coming decades. Skilled workers are needed to obtain the highest level of accuracy from the

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10 PRECiSE GEODETiC iNFRASTRuCTuRE infrastructure, assess the capabilities of the infrastructure as it continues to evolve, and capitalize on advances in technology to improve the accuracy of (or decrease the cost of) the infrastructure. As highlighted in the informal analysis summarized in Box 6.1, representatives from every federal agency that spoke with the committee raised concerns about a growing deficit of well-trained space geodesists and engineers with this necessary knowledge. As a science, geodesy has long been a niche discipline, populated by a small group of experts. Agencies are finding it difficult to replace these highly skilled geodesists as they retire and instead are forced to hire young professionals from other disciplines, such as physicists, whom they must train on the job. Alternatively, U.S. agencies can tap into students educated abroad in countries with strong programs in geodesy. Many American geodesists were trained and supported by the NASA Crustal Dynamics Project (CDP) and the Dynamics of the Solid Earth (DOSE) investigation of the 1980s and early 1990s. These projects focused on addressing important geophysical problems using the nascent geodetic techniques of VLBI, SLR, GPS, and radar altimetry. To achieve the goals of the CDP and DOSE, NASA supported fundamental geodetic research and the training of a generation of graduate stu - dents. Today, geodetic tools pioneered by NASA are routinely used in a wide range of Earth sciences. As NASA’s focus moved from technique development to science applications in the late 1990s, however, opportunities for graduate training in geodesy diminished. Although many NSF-supported efforts (for example, the EarthScope program) rely on these precise geodetic tools, NSF also does not at the moment have a program that specifically targets fundamental geodetic research. One of the recommendations of the National Research Council report Rising above the Gath- ering Storm is particularly relevant to the need for a trained geodetic workforce: “Sustain and strengthen the nation’s traditional commitment to long-term basic research that has the potential to be transformational to maintain the flow of new ideas that fuel the economy, provide security, and enhance the quality of life” (NRC, 2007c). The past decade has seen the emergence of exciting new geodetic imaging techniques and rapid positioning methods. These advances have the potential to address a host of new scientific questions and applications. The development of these emerging technologies in the United States requires long-term support for fundamental research and training for the next generation of geodesists. Although the committee did not collect quantitative demographic data about the geodesy workforce, the anecdotal evidence presented to the committee is sufficient to bring the issue to the fore. Recommendation: A quantitative assessment of the workforce required to support precise : geodesy in the united States and the research and education programs in place at u.S. universities should be undertaken as part of a follow-up study focused on the long-term prospects of geodesy and its applications. NATIONAL GEODETIC INFRASTRuCTuRE: : A MATTER OF COLLABORATION Even a cursory examination of the scope of responsibilities assigned to the various agencies that contribute to the national geodetic infrastructure reveals a complex bureaucratic structure, which might be streamlined and clarified with considerable benefit to the nation. The U.S. geo- geo- detic infrastructure is dispersed and has not previously been considered holistically. It consists of: (1) interdependent precise geodetic techniques (mainly VLBI, GNSS/GPS, and SLR, but also grav - ity, altimetry, and geodetic imaging); (2) standards for data acquisition, archiving, and distribution; (3) a geodetic reference system (the North American Datum of 1983); (4) analysis that combines the data sets to create the ITRF; (5) other derived data products (including, but not limited to,

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109 SuPPORT FOR ThE PRECiSE GEODETiC iNFRASTRuCTuRE atmosphere, ionosphere, and local reference frames); and (6) mechanisms enabling access to those data products. This geodetic infrastructure is a shared national asset that is required for the nation to maintain its global leadership in economic and scientific spheres and to sustain national security. A number of governmental agencies (including NASA, NOAA, DoD, NSF, and USGS) utilize, gov - ern, and support portions of the nation’s geodetic infrastructure; in addition, they each depend on the global geodetic infrastructure. Each has independent missions and requirements, however, and there is no clear chain of responsibility (or authority) for maintaining, upgrading, and augmenting the geodetic infrastructure. Cooperation between and within national agencies and international services is essential to ensure the long-term viability of the global geodetic infrastructure. Fortunately, the discipline of geodesy offers a conceptual framework that has proven successful on a global scale and that could be adapted to satisfy national needs. Recommendation: The united States should establish a federal geodetic service to co - ordinate and facilitate the modernization and long-term operation of the national and global precise geodetic infrastructure to ensure convenient, rapid, and reliable access to consistent and accurate geodetic data and products by government, academic, commer- cial, and public users. The essential functions of a federal geodetic service would include: • Maintaining, upgrading, and augmenting the geodetic infrastructure. • Coordinating the scientific requirements and applications across stakeholders, including federal and state agencies, the scientific community, and commercial and public users. • Selecting a primary provider and clearinghouse agent for data products, such as raw instru - mental data, tracking data, and the necessary metadata. • Coordinating the production and dissemination of data products, especially when the utili - zation of identical products by most or all end-users would be demonstrably beneficial or, in some instances, critical (for example, orbit information for precise navigation). • Supporting emerging geodetic technologies, such as geodetic imaging, and developing the associated tools and data sets to support these technologies. • Fostering fundamental research and education focused on technological and theoretical developments, ongoing deployments, and novel uses of geodetic infrastructure. • Functioning as the lead U.S. partner in the deployment of global infrastructure and interna - tional services. The concept of a federal service is nothing new (consider, for example, the National Weather Service), and neither is the concept of multi-agency coordination. The reason for invoking this concept in the context of geodesy is the enormous surge in demand by all stakeholders, which is expected to continue to increase in the foreseeable future. In developing its concept of a federal geodetic service, the committee considered the role and function of the National Executive Com - mittee on Space-based Positioning, Navigation, and Timing (PNT). Although PNT delivers basic and essential administrative coordination at the national policy and agency level, it is not currently charged with coordination of activities at the data product level, nor is it charged with orchestrating the community to ensure an orderly and effective development and promotion of data and data prod- uct standards. Thus, the federal geodetic service is needed to provide a centralized access point for accurate, consistent geodetic information for government, academic, and commercial users through geodetic

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110 PRECiSE GEODETiC iNFRASTRuCTuRE state-of-the-art technology, such as Internet portals. This geodetic information would include (but technology, would not be limited to): • Satellite orbits (for GNSS/GPS, altimetric, or other geodetic satellites); • Time-dependent station positions; • Earth rotation and orientation parameters; and • Time-dependent topography, gravity field, and geoid information. The concept of a federal geodetic service does not supersede the current missions and strategic plans of the many agencies that contribute to the geodetic infrastructure. Instead, it would remain consistent with, complement, and facilitate these missions. Reflecting previous recommendations, the action items of a federal geodetic service for the recommendations, operation and modernization of the geodetic infrastructure should include: • upgrading the United States’ components of the SLR and VLBI networks, and processing the data from these networks to a level of accuracy equal to or surpassing current best performance; • constructing scientific-quality GNSS/GPS sites throughout the United States, converting CORS sites to PBO standards of accuracy and stability where necessary and practicable; and • transitioning PBO stations from research to operations upon completion of the NSF- funded the EarthScope experiment. In addition to these previously described recommendations, the committee also recommends the federal geodetic service take on coordination and supervisory roles to ensure that all stakehold - ers adopt common standards and common data products, and that these products are generated and distributed using the most efficient, state-of-the-art mechanisms available. Many approaches could satisfy these requirements for a federal geodetic service, all of which could have both strengths and weaknesses. Possibilities include: • Lead agency: A specific agency is assigned the lead responsibility and the necessary resources to head the federal geodetic service. This approach takes advantage of agency expertise and funding, but may be complicated by interagency competition . • Embedded organization: The federal geodetic service activities are consolidated into a new organization housed within one of the existing agencies. This approach could offer a more holistic approach. Precedents and possible models include the National Weather Service and the National Biological Survey. However, funding for the long-term support of the infrastructure might decline sharply unless the budget is protected. • Multi-agency federal service: A formalized, comprehensive structure is established whereby the work of the federal geodetic service is carried out mainly by participating agencies, with clearly spelled-out areas of responsibility and authority. The federal geodetic service would have small staff of its own, with participating agencies operating under an interagency agreement to develop, deploy, and operate the infrastructure and coordinate the product generation and dissemination activities. This concept offers the same advantages as the “lead agency” approach, but with a more holistic outlook. On the other hand, the cost would have to include strategic planning. This approach could follow the model of some of the successful international services described in Chapter 4. It is important that the federal geodetic service take advantage of the existing talent and exper- tise in federal and state governmental agencies, research organizations, academia, and industry. In order for such a service to succeed and be sustainable, innovative, and flexible, it is imperative that that its staff be steeped in state-of-the-art scientific research in precise global geodesy. For this purpose,

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111 SuPPORT FOR ThE PRECiSE GEODETiC iNFRASTRuCTuRE all agencies that support scientific research in this field (for example, DoD, NASA, NOAA, NSF, and USGS) ideally would provide input to the strategic plan of the service. Periodic independent advice from stakeholders in the public and private spheres and those operating at the local and global level would ensure that the service continues to provide reliable access to accurate geodetic information. CONCLuSION The development and deployment of a global precise geodetic infrastructure over the last several decades not only represents a scientific and technological tour de force, but has truly been a classical case of disruptive technology. We cannot imagine our society returning to the days of sextants, spirit levels, and star navigation. Instead, we can imagine autonomous vehicles moving safely at high speed within inches of other vehicles, as well as real-time images of inflating volca - noes or seismic waves rippling across continents. With clocks onboard satellites synchronized with Earthbound clocks to one part in a trillion, we will enable practical uses of general relativity for innumerable scientific and everyday purposes. Because we have yet to explore the applications of much higher spatial and temporal geodetic resolution, we can also expect new science to emerge from a healthy, stable, and well-maintained infrastructure. This report’s recommendation for a new federal geodetic service is aimed at facilitating, and perhaps accelerating, such progress. Finally, if the history of similar services is any guide, it can be anticipated that a federal geodetic service would immediately feed into economic activity, provided that users can safely assume an implied long-term, stable operation in support of the geodetic infrastructure.

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