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Report of the Panel on Optical and Infrared Astronomy from the Ground



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Astronomy and Astrophysics in the New Millennium: Panel Reports 2 Report of the Panel on Optical and Infrared Astronomy from the Ground

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Astronomy and Astrophysics in the New Millennium: Panel Reports SUMMARY As we cross the threshold of the new millennium, astronomy with ground-based optical and infrared (O/IR) telescopes will continue to play its fundamental role in shaping our understanding of the workings of the universe, enriching the golden era of discovery that astronomy has enjoyed in the last decades. As a result of past investments in astronomical facilities, the United States led the world in observational research throughout the 20th century. Our nation has the talent, the knowledge, and the resources to carry this great tradition of leadership into the 21st century, building on a generation of powerful 8-m-class telescopes and anticipating future telescope facilities of unprecedented power and resolution. However, state-of-the-art, ground-based O/IR facilities have grown in scale and complexity so that a new paradigm is needed that balances diversity and coordination. This paradigm focuses effort on unique and complementary capabilities and will enable the efficient development and operation of the next generation of facilities together with the effective use of existing ones. Establishing a common vision within the astronomy community of how these facilities should evolve is the foundation of the recommendations of the Panel on Optical and Infrared Astronomy from the Ground for the coming decade. In this context, the panel proposes three initiatives to encourage the evolution of U.S. O/IR ground-based facilities as a system, by combining and coordinating the assets and efforts of federally funded and independent observatories: A next-generation, giant-aperture, adaptive-optics-equipped telescope whose spatial and spectral resolution will enable the unraveling of complex physical processes in the first galaxies, in nearby planetary systems, and in newborn stars. A unique opportunity exists to bring together federal and independent observatories to build and operate this facility. A large-aperture, very-wide-field synoptic survey telescope that will search the solar system for its ancient materials and open a new time window on astronomical phenomena. This facility has particular resonance with the new role envisioned for the National Optical Astronomy Observatories (NOAO). An enhanced instrumentation program for independent observatories that capitalizes on and encourages the significant investment of

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Astronomy and Astrophysics in the New Millennium: Panel Reports nonfederal funds, both to maximize the operation of U.S. facilities as an efficient system and to increase public access to these facilities. The panel has translated these generalized initiatives into concrete recommendations and prioritized them. MAJOR INITIATIVE, PRIORITY ONE: GSMT Develop the technology to build a giant (30-m class) segmented-mirror, adaptive-optics-equipped, ground-based O/IR telescope (GSMT) and begin its construction within the decade. With diffraction-limited performance down to at least 1 µm, an order-of-magnitude increase in light-gathering power, and a factor-of-4 gain in spatial resolution, GSMT will enable breakthrough science in studies of star and planet formation, stellar populations, and early galaxy evolution. The GSMT’s spatial resolution of 14 milliarcsec at 2 µm and its high spectral resolution in the near-infrared region will significantly exceed the performance of the Next Generation Space Telescope (NGST, scheduled for launch in 2008), providing an important complementarity such as that developed between the Hubble Space Telescope and the Keck telescopes. Furthermore, with the ability to add new instrumentation to GSMT, its capabilities can evolve in response to scientific advances in the early NGST-GSMT era, making it more productive and developing the scientific case for even more advanced facilities on the ground and in space. The GSMT will push relevant technology such as adaptive optics (AO) to its limits, toward what could be the ultimate ground-based telescope in the decades to come. The panel recognizes that, even with anticipated innovation in design and technology, construction of this facility requires an enormous investment of resources, perhaps exceeding $400 million; the operating costs will be similarly large over the facility’s lifetime.1 In response to the challenge of garnering such huge resources, the panel emphasizes its belief that GSMT offers a golden opportunity for partnership between national and independent observatories. To assure the maximum science return, it is essential that a broad scientific community have 1   The estimated costs for ground-based initiatives that appear in the survey committee report (Astronomy and Astrophysics Survey Committee, National Research Council. 2001. Astronomy and Astrophysics in the New Millennium, Washington, D.C.: National Academy Press) include instrumentation, grants, and operations, as described in the preface. These costs for the GSMT are estimated be about $200 million.

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Astronomy and Astrophysics in the New Millennium: Panel Reports access to GSMT; the panel believes that public access should be maximized within the constraints of available funding and that the partnership between the public and private components of U.S. O/IR ground-based astronomy should be strengthened. MAJOR INITIATIVE, PRIORITY TWO: LSST Build a large-aperture (6.5-m class), very-wide-field (~3 deg) synoptic survey telescope (LSST) to produce a periodic digital map of the sky. Its unique combination of large aperture and wide field (~10 deg2) will allow LSST to map the entire sky down to 24th magnitude in a few days. Such capability will enable a wide-area variability experiment (WAVE), a finite-duration project that will accomplish many important scientific goals through a small number of simple survey modes. For example, WAVE on LSST will do the following: Discover and track 10,000 objects in the Kuiper Belt, a largely unexplored, primordial component of our solar system. Locate potentially threatening near-Earth objects (NEOs) down to 300 m in size. Discover and monitor many kinds of variable objects, including supernovae, active galactic nuclei (AGN), and microlensed stars. Produce extremely deep images over hundreds of square degrees for studying the distribution of dark matter through weak gravitational lensing. More than just a telescope, LSST with WAVE will make important strides in data processing, data mining tools, and archiving components and will play a key role in the National Virtual Observatory (NVO) described in the survey committee report. Its data product will have widespread application to all fields of astrophysics and will have enormous educational potential by virtue of its ability to produce a “living sky” that can be downloaded in the classroom. While this unique, state-of-the-art facility could capitalize on the complementary strengths of independent observatories, its mode of operation and data product would make LSST an ideal undertaking for NOAO in its developing new role. MODERATE INITIATIVE, PRIORITY ONE: TSIP Support the Telescope System Instrumentation Program (TSIP) to foster

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Astronomy and Astrophysics in the New Millennium: Panel Reports the more coherent development of public and independent telescope facilities and to increase public access. By substantially increasing its funding of instrumentation for the new generation of large-aperture telescopes at independent observatories, the NSF would encourage the continuation of substantial nonfederal investments, leverage their scientific productivity, and open up new observing opportunities for the entire U.S. astronomy community. The panel therefore proposes TSIP, which would fulfill this critical need and encourage the evolution of U.S. ground-based O/IR facilities as a coherent system. Particularly in an era of enormous investment by the European Southern Observatory, the systemization of all U.S. resources is essential to maintain leadership in the field. Leadership in astronomy is important not only to the discipline itself, but also to the vital role that astronomy plays in improving the scientific literacy of the public. SCIENCE OPPORTUNITIES ANSWERING FUNDAMENTAL QUESTIONS The world’s astronomy community has built powerful tools with which to answer fundamental questions about the birth of galaxies, stars, and planets and to explore the most exotic phenomena in the universe. These tools include (1) a new generation of ground-based O/IR telescopes, (2) the powerful new millimeter-wave arrays—the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and the Submillimeter Array (SMA), with the Atacama Large Millimeter Array (ALMA) to come later in the decade, and (3) the Hubble Space Telescope (HST) and Chandra X-ray Observatory, now in operation, the Space Infrared Telescope Facility (SIRTF) and the Space Interferometry Mission (SIM), on the way, and the Next Generation Space Telescope (NGST), to come. Properly instrumented and supported, these facilities will provide unprecedented opportunities to solve many of the mysteries that 20th century astronomical exploration uncovered. In this chapter, the panel recommends two additional ground-based O/IR facilities—a 30-m-class telescope (GSMT) and a large-aperture synoptic survey telescope (LSST) —which, in concert with the above facilities, will enable astronomers to accomplish the following goals over the next decade or two: Describe the complete cosmological state of the universe with

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Astronomy and Astrophysics in the New Millennium: Panel Reports better than 10 percent accuracy. Using type Ia supernovae and other standard candles, gravitational lenses, and the Sunyaev-Zel’dovich effect, test the Friedmann-Robertson-Walker model back to z~3. Is the universe accelerating as a result of dark energy? Follow the history of star formation and chemical evolution over all of cosmic time. Find and characterize the first generation of stars in the early universe and relate these to the oldest stars in our galaxy and its neighbors. Chart chemical evolution in stars and the interstellar medium through star-by-star studies in nearby galaxies and integrated galaxy-light measurements back to the earliest galaxies. Balance the baryon budget: describe the location and nature of all the baryons through cosmic time. Test the hierarchical model of galaxy formation: observe and analyze the assembly of galaxies from the earliest star systems. Follow the buildup of large-scale structure from reionization to the present day and connect the evolution of individual galaxies to their environment within large-scale structure. Map the dark matter and galaxy distributions with sufficient precision to understand the role of dark matter in galaxy formation and obtain clues to its nature. Connect the formation of supermassive black holes to galaxy formation and evolution. Discover the epoch of black hole formation, the dynamics of the process, and the relation to star formation in the nuclei of galaxies. Understand better the physical processes in active galactic nuclei and solve the riddle of gamma-ray bursts. Examine in detail the processes of star and planet formation. Describe the accretion process that forms a star, including the physical properties of the raw material and the dynamic processes from molecular cloud formation to nuclear ignition. Study the evolution of planetary disks and observe the building of planets around nearby stars, from Kuiper Belt objects (KBOs) at the 100-AU zone to the 1-AU zone, where Earth-like worlds could be formed. Analyze the surviving building blocks of the solar system. Map the Kuiper Belt in our solar system and measure the physical characteristics of KBOs as examples of the primordial material that built the planets. Identify all NEOs whose impact with Earth could have catastrophic consequences. Take a census of the planetary populations around other stars. Understand the relationship between brown dwarfs and planets and the distribution of giant planets in neighboring systems. Search for worlds that could, or already do, support life as we know it.

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Astronomy and Astrophysics in the New Millennium: Panel Reports These are ambitious goals, and ground-based O/IR facilities will play a substantial, often crucial, part in achieving them. Despite the large foreign investments around the world in ground-based astronomy, the United States is well positioned to maintain its leadership role in this field. EXPLOITING THE DIVERSE, UNIQUE FACILITIES OF U.S. GROUND-BASED O/IR ASTRONOMY Astronomers now probe the physics of exotic and extreme environments using observations across the electromagnetic spectrum, ranging from radio waves to gamma rays and everything in between. Ground-based O/IR research remains at the heart of this endeavor. Ground-based spectroscopic observations have been crucial to research with the HST for such diverse topics as high-redshift galaxies, the extragalactic distance scale and cosmological parameters, and stellar populations in the Milky Way and other nearby galaxies. The study of radio galaxies relies on a combination of radio, optical, and infrared (IR) data, as does the goal of linking the evolution of the interstellar medium to stellar evolution. The x-ray halos of galaxies and the hot interstellar gas in rich clusters are being understood thanks to both space-based observations and ground-based optical data, and the recent discovery that gamma-ray bursts take place in distant galaxies, making them the most energetic known phenomenon, is the result of hard-won spectroscopic data from the Keck telescopes and rapid-response imaging from a variety of ground-based instruments. The ambitious scientific program outlined above requires a broad suite of telescopes with a range of aperture sizes and powerful state-of-the-art instrumentation employing the latest array detectors. Ground-based O/IR facilities available to U.S. astronomers include both national and independent installations in a unique combination that has kept U.S. astronomy strong. Remarkably, most of the glass resides at independent observatories, but the National Science Foundation’s (NSF’s) role is nevertheless vital to the health of the entire enterprise: NSF not only supports NOAO and Gemini but also plays a crucial role at the independent observatories by virtue of its grant support for research and instrumentation. Strong competition for leadership in astronomy is now coming from the European Southern Observatory (ESO), which has made huge investments at two Chilean observatories. The most recent of the investments was for the Very Large Telescope (VLT), four 8-m telescopes at

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Astronomy and Astrophysics in the New Millennium: Panel Reports Cerro Paranal costing approximately $700 million. Eight first-generation instruments are under construction at a cost of approximately $90 million. An ongoing instrumentation program funded at $10 million per year is anticipated to provide state-of-the art facilities throughout the decade. A world-class interferometer is also under construction for the VLT. Early results from the VLT are impressive. In addition, ESO has announced its intention to build a truly enormous telescope, currently planned to have a 100-m aperture; this billion-dollar-plus initiative is unprecedented in the history of ground-based astronomy. To meet this challenge, the United States must use its unique combination of federal, state, and private resources to best advantage. The spirit of independence and individual initiative that has characterized U.S. ground-based O/IR astronomy should continue, for it has had highly productive and creative results. But federal resources are sufficiently scarce, and the need at both national and independent observatories so acute that a greater degree of cooperation is urgently needed. Put simply, the suite of U.S. observatories should function as a coherent system to ensure that U.S. astronomers will have the means to participate fully in pursuing the fundamental goals outlined above. Although the recommended new facilities and programs described below are completely justified by scientific arguments alone, the panel sees as equally important the additional overarching goal of strengthening the system and creating a process for its development. To reach this goal, NSF and other agencies that fund O/IR astronomy should appreciate all the elements of the U.S. O/IR system and implement policies that guide the system’s development so that federal funding will achieve maximum science and maximum opportunity. Implicit in this new goal is a changing role for NOAO. The McCray report, A Strategy for Ground-Based Optical and Infrared Astronomy,2 and the AURA-sponsored study on the future of NOAO3 emphasized that to be a more effective component of the U.S. ground-based O/IR system, NOAO must have as its first priority to represent the entire U.S. astronomy community, carrying on activities that benefit all. These activi- 2   Panel on Ground-Based Optical and Infrared Astronomy, National Research Council. 1995. A Strategy for Ground-Based Optical and Infrared Astronomy (Washington, D.C.: National Academy Press); also known as the McCray report after the panel’s chair, Richard McCray. 3   Association of Universities for Research in Astronomy, Inc./NOAO. 2000. Building the Future: NOAO Long Range Plan: 2001–2005 (Washington, D.C.: AURA).

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Astronomy and Astrophysics in the New Millennium: Panel Reports ties will include providing the scientific leadership and technical expertise needed for building the largest facilities, identifying and providing complementary capabilities that support the suite of large telescopes, and representing U.S. interests in efforts that develop as collaborations, either between public and private institutions or with international partners. In the future, NOAO will probably run unique facilities in preference to nonunique ones; as well, it could play an important, multifaceted role in coordinating the entire suite of U.S. ground-based O/IR facilities. MAJOR INITIATIVE, PRIORITY ONE: DEVELOP AND BUILD A NEXT-GENERATION GROUND-BASED TELESCOPE (GSMT) MISSION DESCRIPTION The panel recommends that highest priority be given to the design of a giant (30-m class) segmented-mirror, AO-equipped, ground-based O/IR telescope (GSMT), with the goal of beginning construction before the end of the decade. The GSMT will be a filled-aperture, diffraction-limited telescope with atmospheric correction by AO down to at least 1 µm. It will achieve order-of-magnitude gains over any extant ground-based O/IR telescope and will provide substantial gains in spatial resolution and near-IR high-resolution spectroscopy even over NGST, for which it will be an essential complement (Figure 2.1). The facility will achieve substantial breakthroughs in the science covered in the NASA Origins theme. Especially in view of the ESO initiative to build even larger, more ambitious ground-based telescopes over a substantially longer timescale than this decade, the successful development of a next-generation ground-based telescope, accessible to all U.S. astronomers and contemporaneous with NGST, is essential for maintaining the tradition of U.S. leadership in astronomy. The ESO proposal for a 100-m-class telescope would offer even more spectacular gains for many kinds of observations, but it is the opinion of the panel that the proposal is too ambitious for the current decade and that an intermediate step, to a 30-m telescope, would be optimal in terms of science, technology, and allocation of resources. Of particular importance, the panel believes, is that a next-generation, ground-based facility be available during the lifetime of NGST. The GSMT will operate over the wavelength range from 0.3 to

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Astronomy and Astrophysics in the New Millennium: Panel Reports FIGURE 2.1 The performance of a 30-m ground-based telescope (GSMT) is compared with that of NGST for point sources for a number of spectral resolutions over a range of wavelengths. The vertical axis is the ratio between the S/N achieved for an observation of a given duration (for an object much fainter than the sky) by GSMT and the S/N achieved by NGST. Diffraction-limited image quality at all wavelengths and an emissivity of 10 percent are assumed for GSMT NGST’s advantage beyond 4 µm is likely to be even greater owing to improvements in detector dark currents and read noise. Superposed is a line showing atmospheric transmission. The comparison shows that GSMT is substantially more effective than NGST in obtaining moderate-to high-resolution spectra of faint compact objects, especially below 2.5 µm. NGST is more effective at longer wavelengths, at wavelengths blocked by the atmosphere, and for observations done at low spectral resolution. It should also be noted that no spectroscopic capability is planned for NGST below 1.0 µm, nor is GSMT expected to deliver diffraction-limited images below 1.0 µm. Courtesy of L.Ramsey, Pennsylvania State University, 1999. 25 µm, with a field of view (FOV) of ~20 arcmin and expected diffraction-limited images over a ~1 arcmin field ranging from ~8 milliarcsec at 1 µm to 0.2 arcsec at 25 µm and with seeing-limited performance of ~0.5 arcsec in the UV. The telescope will provide diffraction-limited performance with AO for λ≥1.0 µm. Its high spatial resolution and powerful spectroscopic capability will be a true quantum leap over any other existing or planned U.S. facility. At the same time, the immense aperture

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Astronomy and Astrophysics in the New Millennium: Panel Reports of the telescope will, in and of itself, make the GSMT a uniquely powerful facility for partially corrected or uncorrected observations.4 SCIENCE WITH THE GSMT The need for very high spatial resolution and moderate to high spectral resolution, with dramatically increased sensitivity, drives the development of GSMT. When steps of the size proposed are taken, it is often the case that the greatest impact will come from discoveries that cannot be predicted—such is the nature of exploration and discovery in astronomy—and that are a major source of the excitement that surrounds a powerful new facility of this kind. Nevertheless, the panel sees many unique opportunities for GSMT to help answer today’s leading scientific questions. Summarized below are a few of the exciting possibilities. STAR AND PLANET FORMATION The development of the theory of stellar structure and evolution was one of the greatest achievements of 20th century science. Yet this elegant theory, which explains the life cycle of stars, is incomplete in one critical aspect: it does not predict or account for the formation of stars. Despite its key role in processes as diverse as the origin of planetary systems and the evolution of galaxies, star formation is probably the least-understood aspect of the fundamental processes. Nonetheless, over the last quarter of the 20th century impressive advances in our understanding of star formation came from the continued development of new technological observational capabilities from both the ground and space. During this period astronomers learned the following: Stars form continually in our galaxy within the dense cores of giant molecular clouds. 4   In addition to the ESO project, called OWL, there are three other programs in the early planning stages: MAXAT, a 30- to 50-m telescope (New Initiatives Office at NOAO), the 30-m-class CELT (Caltech and the University of California), and ELT, a 25-m scale-up of the HET (Pennsylvania State University and the University of Texas). The GSMT described here corresponds closely with CELT or MAXAT. Although it is too early to judge the future direction of those projects, the panel believes that GSMT could evolve directly from either of them, one from the private, the other from the public sector, or from a joint project created by merging the two.

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Astronomy and Astrophysics in the New Millennium: Panel Reports $5 million to $10 million apiece (the VLT average is $11 million). Furthermore, data storage, analysis, and dissemination costs will be substantial. Fortunately, the investment required is incremental to the funds already expended at both private and public observatories for construction and continued operation of the new telescope facilities. The panel proposes a new investment beginning at $5 million per year in instrumentation for the independent observatories, concentrated on the new 8-m-class telescopes, which would leverage a scientific yield several times over. Although the panel believes that the program originally proposed in the McCray report10 and recently reviewed and endorsed by the Committee on Astronomy and Astrophysics11 provides the framework for the administration of this program, here it emphasizes elements of the McCray report that have not been applied so far. The McCray report recognized that maximizing the quality and quantity of astronomical research in the United States depends on a vigorous investment from NSF; the report also acknowledged NSF’s long-standing commitment to provide wide access to astronomical facilities, so that studies outlined in research proposals and rated as excellent through the peer review process could be carried out at premier facilities, public and private. It is important to recognize that private facilities now support a large fraction of the U.S. astronomy community (~50 percent, according to the NRC report Federal Funding of Astronomical Research12), a situation very different from that existing when Kitt Peak National Observatory was founded in the 1950s. Although there are now many additional new opportunities for astronomical research, including space-based facilities, radio observatories, and data archives, it is abundantly clear that some measure of public access is vital to the health of U.S. astronomy. The panel reaffirms the critical importance of maximizing scientific return and ensuring greater public access, and it emphasizes the crucial importance of regarding all of the U.S. O/IR facilities as a system. The 10   Panel on Ground-Based Optical and Infrared Astronomy, National Research Council. 1995. A Strategy for Ground-Based Optical and Infrared Astronomy (Washington, D.C.: National Academy Press). 11   Committee on Astronomy and Astrophysics, National Research Council. 1999. “On the National Science Foundation’s Facility Instrumentation Program” (Washington, D.C.: National Academy Press), June 2. 12   Committee on Astronomy and Astrophysics, National Research Council. 2000. Federal Funding of Astronomical Research (Washington, D.C.: National Academy Press).

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Astronomy and Astrophysics in the New Millennium: Panel Reports NSF should administer the TSIP so as to achieve all of these objectives. By employing an approach that recognizes the important contribution of nonfederal funds for astronomy, the NSF will encourage independent observatories to participate. To encourage their participation, the TSIP must be broader than the program first implemented, when the NSF’s goal of acquiring telescope time on private facilities dominated the process. Borrowing from the McCray report’s recommendations, the panel strongly advocates the following guidelines: The TSIP should apply to facility instruments for independent observatories only, for which NSF grants at least $1 million in support of the proposed instrument. It would not replace existing Advanced Technologies and Instrumentation (ATI) or Major Research Instrumentation (MRI) programs. Successful proposals that include an offer of observing time would provide nights on the telescope whose value (based on amortized investment and operations) amounts to 50 percent of the granted funds. This 50/50 split properly recognizes the initiative of the independent observatory researchers in bringing nonfederal funds to astronomical research and supports their science while still attending to the important goal of providing observing time for the best peer-reviewed proposals, regardless of institutional affiliation. (The panel also notes a finding from Federal Funding of Astronomical Research that 50 percent of the users of ground-based O/IR facilities have access to independent observatories.) The 50/50 split should not be negotiable: to negotiate it would undermine the cooperative spirit needed to ensure the success of the overall O/IR system. The proposing institution may specify additional guidelines, for example, whether the time is available only on the proposed instrumentation or on all instrumentation, and it may include requests that specify operating modes, for example, minimum observing run duration. Such conditions are to be evaluated along with other aspects of the proposal. In lieu of some or all of the telescope time, proposals may be accepted that offer other comparable benefits to the astronomy community, for example, the production and dissemination of surveys and the archiving of data from this or other instruments on the telescope for which the instrument is proposed. The panel considers the 50/50 split to be an essential part of its guidelines. It represents a fair division in which both communities

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Astronomy and Astrophysics in the New Millennium: Panel Reports benefit. It is clear that a “dollar of telescope time for a dollar of instrumentation funding” does not recognize or encourage the contribution of universities and private institutions in raising funds and does not recompense them for the talent and time of their scientists and engineers in building facilities. On the other hand, an unrestricted NSF grant of funds with no benefit provided to the broader astronomy community would frustrate the aspirations of the scientists who would like to use the unique facilities outside the national observatories. Something for both groups is the only appropriate solution; the 50/50 split has the added benefit of conveying the traditional notion of fairness. Negotiating the split, as was tried previously, promotes competition that can only undermine the goal of cooperation within the system. Effective development of the entire suite of community facilities as a system depends on a common perception of how the parts of that system interact; a common vision of the strengths, deficiencies, and potential evolution; and an implementation plan with some level of feedback and accountability. The panel looks to NOAO for leadership in involving all segments of the community in discussions aimed at evaluating elements of the system, establishing a common vision, and devising plans for the future. Based on the results of these discussions, NOAO should develop a strategic plan for the system that includes an analysis of the benefits, costs, and risks for various prioritized implementation alternatives. Such an analysis would help the NSF decide how to invest its resources, either proactively, through solicitations for particular capabilities or negotiations for telescope time, or through TSIP, in response to instrument proposals (see Figure 2.11). Given the wide variety of instrument capabilities and performance, scientific potential, public benefit, terms of use of telescope time, and importance to the system of O/IR facilities, the choice of successful proposals should be conducted annually by an NSF-constituted peer review committee. Any recommendations from the NOAO-led strategic planning effort should be provided to that NSF committee, but the peer review process should allow a full consideration of all factors. Every year, the NOAO-led, community-based strategic planning group should provide structured feedback to the NSF regarding the perceived efficacy of its investments in meeting the strategic goals of the community. The panel also considered the effectiveness of direct purchase of telescope time by the NSF and concluded that in some circumstances, this could be the most efficient way for the entire community to gain access to a unique capability. However, the panel prefers the TSIP

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Astronomy and Astrophysics in the New Millennium: Panel Reports FIGURE 2.11 With the advent of diffraction-limited imaging on large ground-based telescopes, the center of the Galaxy has provided us with a unique testing ground for theories on galactic nuclei. On the left is an image of stars in the central 1 arcsec×1 arcsec (~0.035 pc) centered on the putative black hole, obtained with the Keck adaptive optics system in a short demonstration (exposure time=2 min). Speckle imaging at Keck over the last 4 years has been able to track the orbits of the brightest stars (right-hand panel), which reach velocities of up to 1400 km s−1 (0.5 percent of the speed of light). This is an example of how progress in instrumentation, adaptive optics in this case, can lead to breakthrough science. Courtesy of A.Ghez, University of California at Los Angeles. approach because it—as opposed to the time purchase option—ensures the production of critically needed instrumentation and provides for community involvement (through peer review) in the types and capabilities of instruments that will be built and made available. For this reason, the panel recommends that the direct purchase of telescope time should be a second option, used sparingly so as not to significantly decrease the resources needed for TSIP, which would be sized according to the instrumentation needs of the independent observatories. It also urges that decisions by the NSF to buy telescope time should be guided by an understanding of the broad needs of the community, as is intended in TSIP. The goal of building a more cohesive ground-based O/IR community—with increased incentives for private fund-raising, continued commitment to allowing public access to premier facilities, and maximized scientific creativity and output—should guide NSF policy through-

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Astronomy and Astrophysics in the New Millennium: Panel Reports out the decade. Without these investments and increased funding for research support, both provided by the NSF grants program, U.S. astronomers will not be able to continue to play their leadership role in the most basic astronomical research and will not be able to take full advantage of the powerful new space telescopes such as Chandra, SIRTF, and NGST. TECHNOLOGY ISSUES The NSF could enhance the system of O/IR facilities through continued investment in the development of technologies that will ultimately enable new capabilities. Development of detectors, especially large-format, near- and mid-IR arrays, is a key area. AO systems to feed near-IR spectrographs are extremely important to reduce background and work in crowded regions of the sky. Large-scale surveys require new, more efficient data-handling techniques. IR interferometry will open a new discovery space for the study of high-surface-brightness objects and may spur the evolution of ground- and space-based filled-aperture telescopes. COST ISSUES The investment for the first complement of VLT instruments is $91 million, with an expected continuing investment of at least $10 million per year. These figures reflect a realistic assessment of the ongoing investment needed to take full advantage of the $500 million investment in new telescopes (excluding the investment for infrastructure at Paranal). With a comparable capital investment and an even greater number of telescopes, a continuing U.S. investment for major instrumentation of at least this magnitude is required. NSF has separate commitments for instrumentation at NOAO and Gemini, and some nonfederal support for instrumentation is available, leading the panel to conclude that an additional $5 million per year for the independent observatories is critically needed. CONTEXT ISSUES The importance of ground-based facilities for space-based telescopes and ground-based radio astronomy is clear. Most astronomical projects, regardless of wavelength domain, have an O/IR component that is

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Astronomy and Astrophysics in the New Millennium: Panel Reports effectively addressed with ground-based O/IR facilities. The data collected should be archived and made available to the astronomy community, following the lead of the National Virtual Observatory (see the report of the Panel on Theory, Computation, and Data Exploration, Chapter 6). Support for instrumentalists is a particularly vital part of this program; the NSF can and should initiate programs that encourage and support instrument builders throughout the community. The greater participation of theoretical astrophysicists in the planning of large programs also needs encouragement and support. OTHER ISSUES The panel received valuable input from groups and individuals advocating programs and projects with particular scientific or technological thrusts. Described below are several that the panel found particularly meritorious: Spurred both by revolutionary advances in large-area detectors and data-processing capability and by the scientific promise of a new generation of large telescopes that can enable the study of large samples, surveys play an increasingly important role in astronomical research. Although the panel’s main recommendations focus on the large individual effort to conduct a repetitive all-sky survey (LSST with WAVE), it is clear that the infrastructure needed for effective use of the vast amount of data collected in this and other surveys must be provided as well. Accordingly, the panel strongly endorses the National Virtual Observatory initiative, which would link many extant and future archives through common standards and protocols and would develop the tools to mine these archives effectively. The panel also calls attention to the substantial data sets from ground-based O/IR telescopes that are not integrated into archives. The development of archives for ground-based data represents a critical link between the independent observatories and the larger astronomy community. The NSF should explore (through NOAO) means for the systematic development of such archives. A new and exciting class of problems could be tackled using highly multiplexed multi-object spectroscopy. While much thought and effort have gone into the development of arguments for imaging facilities having a large AΩ (aperture×field of view), it is also clear that the prospect of being able to work with samples of millions of spectra opens up the possibility of other studies, for example (1) tracing the evolution of

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Astronomy and Astrophysics in the New Millennium: Panel Reports large-scale structure (for 1<z<4) and (2) understanding the dynamical history of our galaxy’s halo by locating and studying the remnant streams from individual merger or infall events. These questions should be pursued by initiating preliminary studies of this type and by understanding how best to develop such a capability, possibly through incorporation into the GSMT facility or later modification of the LSST facility. It is clear that future very large facilities, whether they are in space or on the ground, will not be limited to filled apertures but, through interferometric imaging, will enable trade-offs in collecting area, dynamic range, and angular resolution. Although the panel endorses no specific interferometry facilities for the decade, there is a strong consensus to support development of interferometry techniques and facilities in order to understand those trade-offs. Another important region of parameter space that deserves increased emphasis is the time domain. Diverse science returns, such as MACHO lensing discoveries and AGN reverberation mapping, would be enabled by facilities that provide synoptic capabilities complementary to the proposed LSST with WAVE survey initiative—for example, an array of medium-size telescopes distributed around the world or dedicated photometric/imaging monitoring telescopes. Many of these projects would benefit greatly from automated telescopes, which allow routine but complete observational programs to be carried out with minimal operating costs. In addition to facilities that would target capabilities such as synoptic imaging, there is a need for supporting the specialized but limited projects that have been using the smaller national telescopes, for example, the spectroscopic monitoring of relatively bright stars for periodic and episodic activity, observations that are important for the theoretical modeling of stellar interiors and atmospheres. Recognizing that many important programs can be carried out with telescopes of modest aperture and that NOAO is likely to provide fewer such facilities in the future, the panel urges NSF to seek alternative means of supporting them—for example, by buying observing time at independent observatories or funding the development of specialized instrumentation. The panel was excited by the prospect of new ground-based sites that offer unique windows through the atmosphere. One of these is the very cold site at the South Pole, the other is the very dry site in the Atacama desert of northern Chile. The South Pole site would support wide-field imaging with a 2-m telescope operating in the 2.4- to 5-µm

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Astronomy and Astrophysics in the New Millennium: Panel Reports range, an important capability that would, for example, enable a census of brown dwarfs in the solar neighborhood. Although the availability of CCDs and HgCdTe arrays continues to improve, there is a pressing need for better coordinated, aggressive development of larger format arrays, particularly IR array detectors. Collaboration between NSF and NASA to develop O/IR detectors could yield benefits for both ground- and space-based applications. Laboratory astrophysics studies are crucial for many of the science domains discussed in this chapter. Particularly in studies of stars, where high-resolution spectroscopy enables the detection of thousands of unblended lines, it is essential to identify spectral lines of complex atoms, molecules, and their ions, together with oscillator strengths for these myriad transitions. Furthermore, quantitative models of stars are based on still-improving measurements of opacity, and nuclear physics provides the basis for understanding nucleosynthesis. Of particular relevance for the science described here is the increasing importance of infrared observations, in the study of protostars or in the Galactic center, for example. As researchers probe the environments where stars and planets are born, an understanding of the complicated molecules and solid-state materials that dominate their observations depends on laboratory measurements. Also needed are good transition probabilities for the rare earth elements to probe the changing abundances of r-process and s-process elements, so important to the studies of chemical enrichment in the Galactic halo. Although laboratory work of this nature is supported by a number of federal agencies, the relevant astrophysical work is dependent primarily on NASA and NSF funding. The panel urges both agencies to provide adequate support for the vital laboratory studies upon which so much astronomical work is based. ACRONYMS AND ABBREVIATIONS 2MASS —Two Micron All Sky Survey AGB —asymptotic giant branch AGN —active galactic nuclei ALMA —Atacama Large Millimeter Array AO —adaptive optics ATI —Advanced Technologies and Instrumentation (an NSF program) AU —astronomical unit (150 million km)

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Astronomy and Astrophysics in the New Millennium: Panel Reports CARMA —Combined Array for Research in Millimeter-wave Astronomy CCD —charge-coupled device CELT —California Extremely Large Telescope Chandra —Chandra X-ray Observatory (NASA, launched in 1999) dof —degrees of freedom ELT —Extremely Large Telescope ESO —European Southern Observatory FOV —field of view FTE —full-time equivalent Gemini —NOAO/multinational Northern and Southern Hemisphere 8-m telescope project GSMT —Giant Segmented Mirror Telescope HII —ionized hydrogen HET —Hobby-Eberly telescope HST —Hubble Space Telescope IGM —intergalactic medium IMF —initial mass function IR —infrared ISM —interstellar medium KBOs —Kuiper Belt objects LSST —Large-Aperture Synoptic Survey Telescope MACHO —massive compact halo objects MAXAT —Maximum Aperture Telescope MRI —Major Research Instrumentation (an NSF program) MT —million tons of TNT, a unit of energy NASA —National Aeronautics and Space Administration Origins —a NASA program NEO —near-Earth object NGST —Next Generation Space Telescope NICMOS —the near-infrared camera and multiobject spectrometer on the Hubble Space Telescope NOAO —National Optical Astronomy Observatories NRC —National Research Council NSF —National Science Foundation NVO —National Virtual Observatory O/IR —optical/infrared QSO —quasi-stellar object OWL —Overwhelmingly Large Telescope or Observatory at a World Level, an ESO proposal for a 100-m telescope SDSS —Sloan Digital Sky Survey

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Astronomy and Astrophysics in the New Millennium: Panel Reports SIM —Space Interferometry Mission SIRTF —Space Infrared Telescope Facility SMA —Submillimeter Array TSIP —Telescope System Implementation Program VLT —Very Large Telescope VRI —observations through visual, red, and infrared filters WAVE —Wide Area Variability Experiment WIYN —observatory run by the University of Wisconsin, Indiana University, Yale University, and NOAO

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