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New Worlds, New Horizons in Astronomy and Astrophysics 7 Realizing the Opportunities The preceding chapters of this report present a compelling science program (Chapter 2) and outline the relationship of the federal program to the larger astronomy and astrophysics enterprise (Chapters 3 and 4). They also discuss workforce development and other core activities, the changes in the base program that are prerequisites for substantial new initiatives, and the need to keep existing facilities in balance with the development of new ones (Chapters 5 and 6). This chapter describes the committee’s recommended program. After outlining the process followed in carrying out the Astro2010 survey, this chapter discusses how addressing the three major objectives of the recommended science program requires a particular suite of activities. Next, it argues that this same suite addresses the larger science program outlined in Chapter 2. The recommended activities are then described in more detail as elements of the integrated program for the decade recommended to the three agencies that commissioned this report. PROCESS Prioritization Criteria The approach taken by this survey has been to develop a logical program for the decade 2012-2021 that is firmly aimed at realizing identified science priorities and opportunities, especially the key science objectives established below. The recommended program is rooted in the existing research enterprise and is based in
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New Worlds, New Horizons in Astronomy and Astrophysics part on the availability of new technology that will inspire and enable astronomy and astrophysics in the decade to come. Furthermore, in the development of its recommendations the committee considered the challenges and constraints of the current federal budget environment along with its own independent and critical evaluation of proposed activities. The need for balance across the program was carefully considered. The committee adopted four major criteria as the basis for prioritization of activities: Maximizing the scientific contribution and return identified by the survey process (see Chapter 2); Building on the current astronomy and astrophysics enterprise (see Chapters 3, 4, 5, and 6); Balancing activities that can be completed in the 2012-2021 decade against making investments for the next decade; and Optimizing the science return under highly constrained budget guidelines by assessing activity readiness, technical risk, schedule risk, cost risk, and opportunities for collaboration. Program Prioritization The science case developed by the committee in Chapter 2 served as a principal component of the evaluation of proposed activities that was undertaken by this survey. It was drawn from the questions and discovery areas identified by the five Science Frontiers Panels (SFPs) appointed by the National Research Council (NRC) to assist the committee, namely: Cosmology and Fundamental Physics, The Galactic Neighborhood, Galaxies Across Cosmic Time, Planetary Systems and Star Formation, and Stars and Stellar Evolution. The charge to and principal findings of the SFPs are summarized in Appendix A. The individual SFP reports describe in more detail the science priorities.1 The work of these panels formed the foundation for the prioritization process. 1 See National Research Council, Panel Reports—New Worlds, New Horizons in Astronomy and Astrophysics, The National Academies Press, Washington, D.C., 2011.
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New Worlds, New Horizons in Astronomy and Astrophysics The prioritization process included projects not yet started from the preceding decadal survey, Astronomy and Astrophysics in the New Millennium (AANM).2 The rationale for their review stems from a need to ensure that these research activities are still up to date technologically, that the science questions they tackle remain compelling and a high priority, and that their cost and schedule are still commensurate with the science return. Given the multidecade timescales required for development of major facilities from concept to construction to operation, it should not be surprising that many of these projects have evolved in technical and/or scientific scope since AANM, further motivating their reconsideration. Because of the need for significant technical expertise in developing a prioritized program from a wide array of candidate ongoing and proposed activities, four Program Prioritization Panels (PPPs) were also established by the NRC to assist the committee in studying technical and programmatic issues within the following areas: Electromagnetic Observations from Space (EOS)—activities funded largely by NASA, some with a DOE component; Optical and Infrared Astronomy from the Ground (OIR)—activities funded largely by NSF and private entities, some with a DOE component; Particle Astrophysics and Gravitation (PAG)—activities funded by NASA, NSF, and DOE; and Radio, Millimeter, and Submillimeter Astronomy from the Ground (RMS)—activities funded largely by NSF with some private components. The charge to the PPPs and their principal recommendations for new activities are summarized in Appendix B. The PPPs started with the SFPs’ conclusions on the highest-priority science and then developed a program to address this science optimally. The panels also referred to pertinent NRC reports, as well as reports from the astronomy community. The individual PPP reports contain these and other non-facility recommendations spanning a range of scales.3 Each panel was charged to consider only the potential program within its designated subdiscipline. By design this approach results in a combined program that is too large to be implemented in any reasonable budget scenario. It thus fell to the survey committee to synthesize the panel recommendations with additional consideration for the issues discussed in Chapters 3, 4, 5, and 6, and thereby develop a merged implementable program for the entire astronomy and astrophysics enterprise. 2 National Research Council, Astronomy and Astrophysics in the New Millennium, National Academy Press, Washington, D.C., 2001. 3 National Research Council, Panel Reports—New Worlds, New Horizons in Astronomy and Astrophysics, The National Academies Press, Washington, D.C., 2011.
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New Worlds, New Horizons in Astronomy and Astrophysics Cost, Risk, and Technical Readiness Evaluation As an early step in the survey process (Figure 7.1), the committee issued a request for information to the astronomy and astrophysics community to solicit input on possible future research activities. More than 100 responses proposed significant construction or programmatic activities. Following an initial analysis by the PPPs, the survey committee requested further and more detailed information from a set of activity teams, which was subjected to a novel cost appraisal and technical evaluation (CATE) process (see Appendix C for a detailed discussion of this process). The objective of the CATE process was to judge the readiness, technical risk, and schedule risk for the proposed projects, and then to construct associated cost and schedule estimates. The CATE process was conducted by a private contractor (the Aerospace Corporation) that was hired by the NRC to assist the committee in executing this element of its charge. Throughout the course of the survey, the committee and the PPPs remained engaged with the contractor to ensure that the contractor understood the key aspects of the proposed activities and the key points of analysis required by the panels and the committee. All elements of a project required to produce an initial science result were included in the assessment. The assessment was intended to include technical development and construction costs, as well as operating costs for a nominal 5-year mission or project execution, but not research costs needed to exploit the FIGURE 7.1 Time line showing the sequence of the Astro2010 survey’s activities and its cost appraisal and technical evaluation (CATE) process. The six committee meetings—including the “Jamboree” meeting involving all four Program Prioritization Panels, the Infrastructure Study Group chairs, the Science Frontiers Panel chairs, and the survey committee—held at key process milestones are indicated by the orange diamonds.
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New Worlds, New Horizons in Astronomy and Astrophysics science optimally. For some activities a clear path emerged to deployment from this analysis, while for others it became equally clear that certain milestones would have to be met before the activity could proceed to full implementation. For still other activities, the scientific and technical landscapes were found to be shifting too rapidly for the survey to make a definitive recommendation now, and so a strategy for addressing the science and/or retiring the technical risk is recommended. Budgets A prime task of this survey was to construct a program that is innovative and exciting yet also realistic and balanced in terms of the range and scale of federally supported activities. The committee chose for convenience and clarity to exhibit budgets in the form of unencumbered FY2010 dollars available for new initiatives, and it started by considering the agency-projected budgets. National Aeronautics and Space Administration (NASA) Although the NASA Astrophysics Division’s annual budget has been as high as $1.7 billion in the past,4 it is currently approximately $1.1 billion and projected to remain flat in real-year dollars through 2015, according to the President’s FY2011 budget, and to remain flat thereafter according to NASA input to the committee. This implies a decrease in purchasing power over the decade at the rate of inflation. The committee concluded that this budget outlook allows very little in the way of new initiatives until mid-decade, by which time the James Webb Space Telescope (JWST) should be launched and opportunities for new funding wedges will open up. The committee also considered, as a basis for recommending a program, a more optimistic scenario in which the budget is flat over the decade in FY2010 dollars. National Science Foundation (NSF) Although the overall NSF budget is promised to “double,” or increase by 7 percent each year for 10 years in real dollars, the agency input to the committee was that the Division of Astronomical Sciences (NSF-AST) portion of the budget would remain flat over the decade in FY2010 dollars (requiring approximately 3 percent growth per year in real-year dollars).5 4 Given here in FY2010 dollars; this was during the time of peak expenditure on the James Webb Space Telescope (from Paul Hertz, Chief Scientist, Science Mission Directorate, NASA, “Presentation to the Board on Physics and Astronomy,” April 26, 2006, Washington, D.C., available at http://sites.nationalacademies.org/BPA/BPA_052067. 5 Note that the NSF-AST budget did benefit from a one-time injection of $86 million in American Recovery and Reinvestment Act stimulus money in FY2009.
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New Worlds, New Horizons in Astronomy and Astrophysics In this case, once existing obligations are honored and operations at the Atacama Large Millimeter/submillimeter Array (ALMA) and the Advanced Technology Solar Telescope (ATST) rise to the planned full levels by 2017, the committee found that the only way there can be any significant new initiative is through very large reductions in the funding for existing facilities and budget lines. Accordingly, the committee considered a more optimistic scenario that it believes to be justified given the success and promise of the NSF-AST program. In this scenario, NSF-AST participates fully in the aforementioned doubling of the NSF overall budget, and so its purchasing power would grow at 4 percent per year for 10 years. This scenario was used by the committee as a basis for building its recommended program. In considering large ground-based construction projects, the committee assumed that the Major Research Equipment and Facilities (MREFC) line would be appropriate for new NSF-AST-supported projects to compete for—once ALMA is largely completed in 2012, and noting that $150 million of ATST funding is still planned to be drawn from the line until 2017. The committee also noted that in practice, an important limitation on the construction of new facilities under MREFC is the capacity of the NSF-AST budget to provide appropriate running costs, including operations, science, and upgrades, once construction is completed. Department of Energy (DOE) In seeking guidance on possible budget scenarios for activities that might be funded by DOE, some in partnership with the NSF Division of Physics (NSF-PHY), the committee looked to the 2009 report from the High Energy Physics Advisory Panel (HEPAP) and its Particle Astrophysics Scientific Assessment Group (PASAG) that reexamined current and proposed U.S. research capabilities in particle astrophysics under four budgetary scenarios.6 The committee first adopted the more optimistic HEPAP-PASAG scenario, Scenario C, under which there is also a budget doubling as the basis for developing its program. It then considered the HEPAP-PASAG Scenario A, in which the total budget is constant in FY2010 dollars.7 6 U.S. Department of Energy, Report of the HEPAP Particle Astrophysics Scientific Assessment Group (PASAG), October 23, 2009, available at http://www.er.doe.gov/hep/files/pdfs/PASAG_Report.pdf. 7 The HEPAP-PASAG report concluded that after allowance for a direct-detection dark matter program—which is not within the purview of this survey—Scenario A did not provide enough resources to support major hardware contributions to either LSST or JDEM (U.S. Department of Energy, Report of the HEPAP Particle Astrophysics Scientific Assessment Group (PASAG), 2009.
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New Worlds, New Horizons in Astronomy and Astrophysics SCIENCE OBJECTIVES FOR THE DECADE The compelling science promise outlined in this report offers opportunities for making discoveries—both anticipated and unanticipated—for which the next decade will be remembered. The ingenuity and means are at hand to address the most promising and urgent scientific questions raised by the SFPs and summarized in Chapter 2, albeit on various timescales. The committee concluded that the way to optimize and consolidate the science return with the resources available is to focus on three broad science objectives for the decade—targets that capture the current excitement and scientific readiness of the field, and are motivated by the technical readiness of the instruments and telescopes required to pursue the science. These targets—Cosmic Dawn: Searching for the First Stars, Galaxies, and Black Holes; New Worlds: Seeking Nearby, Habitable Planets; and the Physics of the Universe: Understanding Scientific Principles—are the drivers of the priority rankings of new activities and programs identified below. However, they form only part of the much broader scientific agenda that is required for a healthy program. Cosmic Dawn: Searching for the First Stars, Galaxies, and Black Holes Astronomers are on the threshold of finding the root of our cosmic origins by revealing the very first objects to form in the history of the universe. This step will conclude a quest that is akin to that of an anthropologist in search of our most ancient human ancestors. The foundations for this breakthrough are already in place with the current construction of ALMA, which will detect the cold gas and the tiny grains of dust associated with the first large bursts of star formation, and JWST, which will provide unparalleled sensitivity to light emitted by the first galaxies and pinpoint the formation sites of the first stars. This powerful synergy between JWST and ALMA applies not only to these first objects in the universe, but also to the generations of stars that followed them. The emergence of the universe from its “dark ages,” before the first stars ignited, and the buildup of galaxies like our own from the first primordial seeds will be recorded. A staged development program is proposed beginning with the Hydrogen Epoch of Reionization Array-I (HERA-1) telescopes that are already under construction. The reionization of the primordial hydrogen by these first stars will be constrained by detections of cool gas from the dark ages with the first generation of HERA experiments. Much of what has already been learned has been informed by the results of theoretical investigations and sophisticated numerical simulations, and these are likely to play an increasingly important role in planning and interpreting future observations. However, completing the record of galaxy formation, and understanding the composition and nature of these faint distant early galaxies, will require a new generation of large ground-based telescopes. A number of activities proposed to
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New Worlds, New Horizons in Astronomy and Astrophysics this survey would address this goal. For example, a submillimeter survey telescope such as CCAT (formerly the Cornell-Caltech Atacama Telescope) would be capable of identifying the dusty young galaxies that ALMA plans to study in detail. The 20- to 40-meter optical telescopes, known collectively as Giant Segmented Mirror Telescopes (GSMTs), that are planned for construction over the coming decade would render within spectroscopic reach the most distant objects imaged by JWST. A GSMT would allow scientists to determine the mass of the first galaxies and to follow the buildup of the first heavy elements made inside stars. As well as discovering how infant galaxies grow, astronomers would also understand how they shine and affect their surroundings through outflows of gas and ultraviolet radiation. A major challenge to JWST and GSMT is to understand how and why the birth rate of stars grew, peaked when the universe was a few billion years old, and has now declined to only a few percent of its peak value. The star-formation history of the universe can also be tracked by gamma-ray observations made with the proposed Atmospheric Čerenkov Telescope Array (ACTA): as high-energy gamma rays from the distant universe are converted into electrons and positrons, they can indicate how much star formation there has been along the way. The era when the strong ultraviolet radiation from the first stars ionizes the surrounding hydrogen atoms into protons and electrons is known as the epoch of reionization, which can be studied directly using sensitive radio telescopes. These should determine when reionization occurred, and they would inform the design of a proposed new telescope that would measure how the cavities of ionized hydrogen created by the light from the first generations of stars, galaxies, and black holes expand into the surrounding gas. In the long term, realization of the full potential of this approach would require in the following decade a detailed mapping of the transition in the early universe from protogalactic lumps of gas and dark matter into the first objects, a goal of the proposed worldwide effort to construct the low-frequency Square Kilometer Array (SKA-low) as discussed in the subsection “Radio, Millimeter, and Submillimeter” under “OIR and RMS on the Ground” in Chapter 3. Studies of the intergalactic medium, which accounts for most of the baryons in the universe, at more recent times could be transformed by an advanced UV-optical space telescope to succeed the Hubble Space Telescope (HST), equipped with a high-resolution UV spectrograph. Galaxies are composed not just of stars orbiting dense concentrations of dark matter. They also contain gas and central, massive black holes. When the gas flows rapidly onto a central black hole, it radiates powerfully and a quasar is formed. Meanwhile the black hole rapidly puts on weight. It is already known from observations that these black holes can grow very soon after the galaxies form. However, the manner in which this happens is still a mystery. These accreting black holes can be seen back to the earliest times using the proposed space-based Wide-Field Infrared
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New Worlds, New Horizons in Astronomy and Astrophysics Survey Telescope (WFIRST) and the International X-ray Observatory (IXO), and the masses of the black holes can be measured using a GSMT. Simulations show that the first galaxies were likely relatively small and that the giant galaxies observed today grew by successive mergers. Observations of mergers should be possible using JWST, ALMA, WFIRST, and GSMT. As galaxies merge it is likely that their black holes merge as well. The proposed Laser Interferometer Space Antenna (LISA) mission will search for the signatures of these processes by scanning the skies for the bursts of gravitational waves produced during these early mergers when the black holes are relatively small. (LISA will not be sensitive to the mergers of more massive black holes.) An important part of the strategy is to search for associated flashes of electromagnetic radiation that are expected as part of these events. The proposed Large Synoptic Survey Telescope (LSST) will be ideally suited to this task and, working with a GSMT, should make it possible to pinpoint and date the sites of black hole merger events. In summary, this survey committee recommends improving understanding of the history of the universe by observing how the first galaxies and black holes form and grow. To do so requires that current capabilities be supplemented with the priority ground- and space-based activities identified in this survey; see Box 7.1. New Worlds: Seeking Nearby, Habitable Planets The search for exoplanets is one of the most exciting subjects in all of astronomy, and one of the most dynamic, with major new results emerging even as this report was being written. As described in Chapter 2, an unexpectedly wide variety of types and arrangements of planets have been identified—even a few systems with some resemblance to our solar system. What has not been found yet is an Earth-like planet, that is, a terrestrial body with an atmosphere, signs of water and oxygen, and the potential to harbor life. This survey is recommending a program to explore the diversity and properties of planetary systems around other stars, and to prepare for the long-term goal of discovering and investigating nearby, habitable planets. This program is likely to be informed by theoretical calculations and numerical simulations. Locating another Earth-like planet that is close enough for detailed study is a major challenge, requiring many steps and choices along the way. The optimum strategy depends strongly on the fraction of stars with Earth-like planets orbiting them. If the fraction is close to 100 percent, then astronomers will not need to look far to find an Earth-like planet, but if Earth-like planets are rare, then a much larger search extending to more distant stars will be necessary. With this information in hand, ambitious planning can begin to find, image, and study the atmospheres of those Earth-like planets that are closest to our own. Equally important to the characterization of an Earth-like planet is to understand such planets as a class.
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New Worlds, New Horizons in Astronomy and Astrophysics BOX 7.1 Implementing a Cosmic Dawn Science Plan Carry out simulations and theoretical calculations to motivate and interpret observations aimed at understanding our cosmic dawn. Find and explore the epoch of reionization using hydrogen line observations starting with the HERA telescopes that are already under construction. Use CCAT to identify the best candidate young galaxies for study with submillimeter observations. Study these galaxies in detail using ALMA; in particular, monitor how fast the gas that they contain is being converted into stars. Use JWST to measure the rate at which stars are being formed out of gas, and understand their role in reionizing the universe. Use GSMT to study the early evolution of infant galaxies using optical and infrared spectroscopy. Use GSMT and IXO to monitor the exchange of gas between the galaxies and the surrounding intergalactic medium. Study the rate of formation and growth of black holes in the nuclei of young galaxies using IXO and WFIRST. Employ LISA to measure the rate at which young galaxies merge through observing powerful bursts of gravitational radiation produced during the coalescence of their nuclear black holes. Study the oldest stars in nearby galaxies using GSMT. NOTE: ALMA, Atacama Large Millimeter/submillimeter Array; CCAT, formerly the Cornell-Caltech Atacama Telescope; GSMT, Giant Segmented Mirror Telescope; HERA, Hydrogen Epoch of Reionization Array; IXO, International X-ray Observatory; JWST, James Webb Space Telescope; LISA, Laser Interferometer Space Antenna; and WFIRST, Wide-Field Infrared Survey Telescope. Although our own solar system has four such terrestrial bodies, the frequency of formation of terrestrial planets, mass distributions as a function of stellar mass, and orbital arrangements are not understood. Generating a census of Earth-like or terrestrial planets is the essential first step toward determining whether our own home world is a commonplace or rare outcome of planet formation. We have various complementary means of building up a census of Earth-like planets. The ground-based radial velocity and transit surveys are most sensitive to large planets with small orbits, as is the Kepler satellite, although it should be capable of detecting Earth-size planets out to almost Earth-like orbits. Together these techniques will determine the probability of planets with certain orbital characteristics around different types of stars. To complete the planetary census, it will be necessary to use techniques that are sensitive to Earth-mass planets on large orbits. One such technique is called gravitational microlensing, whereby the pres-
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New Worlds, New Horizons in Astronomy and Astrophysics ence of planets is inferred8 through the tiny deflections that they impose on passing light rays from background stars. A survey for such events is one of the two main tasks of the proposed WFIRST satellite. Because microlensing is sensitive to planets of all masses having orbits larger than about half of Earth’s, WFIRST would be able to complement and complete the statistical task underway with Kepler, resulting in an unbiased survey of the properties of distant planetary systems. The results from this survey will constrain theoretical models of the formation of planetary systems, enabling extrapolation of current understanding to systems that will still remain below the threshold of detectability. However, in addition to determining just the planetary statistics, a critical element of the committee’s exoplanet strategy is to continue to build the inventory of planetary systems around specific nearby stars. Therefore, this survey strongly supports a vigorous program of exoplanet science that takes advantage of the observational capabilities that can be achieved from the ground and in space. The first task on the ground is to improve the precision radial velocity method by which the majority of the close to 500 known exoplanets have been discovered. The measured velocity amplitude of a star depends on the ratio of the planetary to the stellar mass, and on the distance from the star, with a Jupiter-mass body at 5 times the Earth-Sun distance from a Sun-like star producing a 12-meter-per-second signal and an Earth at the Earth-Sun location just a 6-centimeter-per-second signal. Improving the velocity precision will allow researchers to measure the masses of smaller planets orbiting nearby stars. Using existing large ground-based or new dedicated mid-size ground-based telescopes equipped with a new generation of high-resolution spectrometers in the optical and near-infrared, a velocity goal of 10 to 20 centimeters per second is realistic. This could allow detection of bodies twice or three times the mass of Earth around stars the mass of the Sun, and truly Earth-mass planets around stars a factor of two or three less massive than the Sun. The radial velocity technique is also of high value when paired with complementary techniques. For example, transits can determine planet sizes and, in combination with the mass found from another technique, yield clues regarding the bulk planetary compositions—just as we know that Earth is mostly rock and iron from its mass and size and a calculation of the average density. Improved precision astrometry and interferometric techniques that are sensitive to planets at larger separations could not only detect new Jupiter-class planets but also study known planetary systems in combination with radial velocity methods so as to resolve the ambiguity regarding true mass as distinct from the inferred minimum mass. Success with endeavors to determine the solar neighborhood planetary census will be very important because knowing that Earth-mass planets exist around nearby stars will give much higher confidence that a future space mission to 8 Neither the planet nor the planet host star is detected outside of the microlensing event.
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New Worlds, New Horizons in Astronomy and Astrophysics doubling funding scenario, some funding could be available by the last few years of the decade; in the flat budget scenario, few if any operations funds would be available in this decade. However, the GSMT projects are at a pivotal point where some form of commitment from the U.S. government at this time will encourage additional collaboration and is crucial to having the projects go forward at all. Owing to the highly compelling science case for this class of telescope, the committee recommends immediate selection by NSF of one of the two U.S.-led GSMT projects for a future federal investment that will secure a significant public partnership role in the development, the operation, and telescope access. This action should facilitate access to and optimize the benefit of the largest ground-based telescopes for the entire U.S. community, by leveraging the significant private and international investments in this frontier endeavor. The committee further recommends as a goal that access should be sought at the level of at least a 25 percent share. This share could be secured through whatever combination of construction (that is, MREFC), operating funds, and instrumentation support is most favorable. The committee believes that access to a GSMT will, as opportunities opened by large telescopes have in the past, transform U.S. astronomy by means of its broad and powerful scientific reach, and that federal investment in a GSMT is vital for the United States to be competitive in ground-based optical astronomy over the next two decades. These are the main reasons for its strong recommendation by the survey. The third-place ranking reflects the committee’s charge, which required the prioritization to be informed not only by scientific potential but also by the technical readiness of the components and the system, the sources of risk, and the appraisal of the costs. LSST and several of the concatenation of candidates for the Mid-Scale Innovations Program were deemed to be ahead of GSMT in these areas. Priority 4 (Large, Ground). Participation in an Atmospheric Čerenkov Telescope Array (ACTA) The last decade has seen the coming of age of very high energy (TeV) astronomy. Very high energy gamma-ray photons are observed from cosmic sources through the flashes of Čerenkov light that they create in Earth’s atmosphere. These events can be observed by large telescopes on the ground on moonless and cloudless nights, and the directions and the energies of individual photons measured. After a long U.S.-led period of development of this technique which yielded the discovery of a handful of sources, the field has taken off. The European facilities, HESS in Namibia and MAGIC in the Canary Islands, together, now, with the U.S. facility VERITAS in Arizona, have discovered 100 sources. These include active galactic nuclei, pulsars, supernova remnants, and binary stars. Astrophysicists have learned much about particle acceleration and can now rule out some models of
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New Worlds, New Horizons in Astronomy and Astrophysics fundamental physics as well as constrain the properties of putative dark matter particles. Further progress is now dependent on building a larger facility exploiting new detector technology and a larger field of view so that the known sources can be studied in more detail and the number of sources can be increased by an order of magnitude (Figure 7.10). Both the U.S. and the European communities are developing concepts for a next-generation array of ground-based telescopes with an effective area of roughly 1 square kilometer. The U.S. version of this facility (AGIS, the Advanced Gamma-ray Imaging System) was evaluated by the survey and the total cost, estimated to exceed $400 million, was considered too expensive to be entertained, despite technical risk being medium low. The European Čerenkov Telescope Array (CTA) is in a more advanced stage, and there is advantage in sharing the costs and operations in a Europe-U.S. collaboration. The committee recommends that the U.S. AGIS project join CTA for collaboration on a proposal that will combine the best features of both existing projects. Funding availability is likely to permit U.S. participation only as a minor partner, but the promise of this field is so high that continued involvement is strongly recommended. U.S. funding should be shared among DOE, NSF-AST, and NSF-PHY, as happened with VERITAS, and a notional $100 million spread between the agencies over the decade is recommended. Given the large project cost uncertainties, the current lack of a unified project plan, the project ranking, and the likely budget constraints in the coming decade, it will be necessary for the agencies to work quickly with the AGIS/CTA group to define a scope of U.S. involvement that is both significant and realistic. FIGURE 7.10 ACTA would be, like the pictured VERITAS (Very Energetic Radiation Imaging Telescope Array System), an array of Čerenkov telescopes used to detect very high energy (TeV) gamma rays emanating from astrophysical sources. The proposed ACTA telescope would be a larger-scale international version of this facility and similar ones located in Namibia and the Canary Islands that would increase the sensitivity by roughly an order of magnitude. SOURCE: Image courtesy of Steve Criswell, SAO.
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New Worlds, New Horizons in Astronomy and Astrophysics The recommendation for ongoing U.S. involvement in TeV astronomy is based largely on the demonstrated recent accomplishments of this field and the prospect of building fairly quickly a much more capable facility to address a broad range of astronomy and physics questions over the next decade. Recommendation for New Ground-Based Activities—Medium Project Only one medium project is called out, because it is ranked most highly. Other projects in this category should be submitted to the Mid-Scale Innovations Program for competitive review. Priority 1 (Medium, Ground). CCAT CCAT (formerly the Cornell-Caltech Atacama Telescope) would be a 25-meter telescope operating in survey mode over wavelengths from 200 microns to 2 millimeters (Figure 7.11). CCAT is enabled by recent, dramatic advances in the ability to build millimeter-wave cameras with more than an order of magnitude more spatial elements than previously possible. This technical advance will enable a powerful submillimeter and millimeter telescope that can perform sensitive imaging surveys of large fields. ALMA, operating over the same band, is scheduled to begin full operations in 2014 and will produce high-resolution images and spectra of faint, and in some cases distant, sources. However, ALMA has a small field of view and is therefore inefficiently used to find the sources that it studies. CCAT will therefore be an essential complement to ALMA. It would excel as a sensitive survey facility, both for imaging and multiobject spectroscopy, with a field of view 200 times larger than that of ALMA. With a broad scientific agenda, CCAT will enable studies of the evolution of galaxies across cosmic time, the formation of clusters of galaxies, the formation of stars in the Milky Way, the formation and evolution of planets, and the nature of objects in the outer solar system. The committee estimates a total development and construction cost of $140 million and an estimated start of operations in 2020.24 The technical risk was assessed as medium. It is recommended that NSF plan to fund $37 million of the construction cost. This funding amount, as well as a potential NSF contribution to operations at the requested level of $7.5 million, is contingent on an arrangement being negotiated that allows broad U.S. astronomical community access to survey products and competed observing time on a facility that should significantly enhance the U.S. scientific productivity of ALMA. 24 The total construction cost is estimated to be $110 million, and so with a third share for the federal government CCAT falls in the “medium” cost category.
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New Worlds, New Horizons in Astronomy and Astrophysics FIGURE 7.11 CCAT is a 25-meter telescope located at 18,500 feet elevation close to ALMA in Chile. The mirror surface has active control. CCAT will operate from 0.3 to 1.4 millimeters (with a goal of 0.2 to 3.5 mm) with a 10- to 20-arcminute field of view and diffraction-limited angular resolution of 10 × (wavelength in millimeters) arcsecond. Highly sensitive bolometer arrays with more than 10,000 sensors using superconducting transition edge sensor technology are envisaged. The flux sensitivity is limited by source confusion to around 1 mJy. SOURCE: M3 Engineering/CCAT/Caltech. CCAT is called out to progress promptly to the next step in its development because of its strong science case, its importance to ALMA, and its readiness. Small Additions and Augmentations to NSF’s Core Research Program As discussed in Chapters 5 and 6, several changes to NSF’s core research program in ground-based astronomy are recommended. Collected here is an unranked list of the five components for which increases in funding are deemed most needed. Programs that are not mentioned are assumed to proceed with existing budgets, subject to senior review recommendations, although the committee emphasizes the importance of many small elements of the core research programs described in Chapter 5.
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New Worlds, New Horizons in Astronomy and Astrophysics Advanced Technologies and Instrumentation Competed instrumentation and technology development are supported, including computing at astronomical facilities in support of the research program, as described in Chapter 5. The current level of funding is roughly $10 million per year, and the survey’s proposal is to increase this to $15 million per year to accommodate key opportunities including, especially, advanced technology in adaptive optics development and radio instrumentation. Astronomy and Astrophysics Research Grants Program Competed individual investigator grants, as described in Chapter 5, provide critical support for astronomers to conduct the research for which the observatories and instruments are built. The current funding level has fluctuated, especially because of the welcome injection of ARRA funding, but the rough baseline is $46 million per year. An increase of $8 million for a total of $54 million per year is recommended. This increment should include the support of new opportunities in Laboratory Astrophysics. Gemini Augmentation An international partnership supports operations and instrumentation at the two international Gemini telescopes. As described in Chapter 6, the imminent withdrawal of the United Kingdom from the partnership will require that additional support be provided by the remaining partners. Set against this need is a desire to operate the telescopes more efficiently and achieve significant savings in operations costs. An augmentation of $2 million to the annual budget is recommended subject to the results of NSF’s exploring a restructuring of the management and operations of Gemini and acquiring an increased share of the observing time, as discussed in Chapter 6. Telescope System Instrument Program The TSIP trades competed support of telescope instrumentation on privately operated telescopes for competed observing time open to the entire U.S. astronomical community. As described in Chapter 6, this is a vital component of the OIR system that was instituted following advice presented in the 2001 decadal survey. It is currently supporting new telescope instrumentation at an average rate of roughly $2 million to $3 million per year and an increment to $5 million per year is recommended.
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New Worlds, New Horizons in Astronomy and Astrophysics Theory and Computation Networks A new competed program coordinated with a similar program proposed to NASA, Theory and Computation Networks will, as described in Chapter 5, support coordinated theoretical and computational attacks on selected key projects that feature prominently in the science program and are judged ripe for such attention. An NSF annual funding level of $2.5 million is recommended. RECOMMENDATIONS FOR THE AGENCIES The committee used a sandchart tool as an existence proof that its recommended phased program for each agency—NASA, DOE, and NSF—would fit within the suggested and envisioned decadal budget. It is recognized that budgets may indeed shift as the decade proceeds, relative to the committee’s assumptions. Therefore, the charts are perceived as most useful for conveying the committee’s intended staging of the different activities it has recommended. NASA Astrophysics The recommended program for NASA has been constrained to fit within an Astrophysics Division budget for the decade that is flat in FY2010 dollars. In round numbers, $3.7 billion is available for new initiatives and augmentations to existing programs within the 2012-2021 budget submissions. As indicated by the example shown in Figure 7.12, it is possible to accommodate the recommended program within the profile, launching WFIRST by the end of the decade; enhancing the Explorer program; getting a good start on LISA; carrying out the IXO, New Worlds, and Inflation Probe technology development programs; making essential augmentations to the core research program; and contributing to SPICA. Of course, there are many contingencies. For example, if LISA fails to satisfy either of the conditions specified by the survey committee, or if WFIRST, as recommended here, becomes a collaborative mission, it could be possible to accelerate IXO. The committee was charged by NASA to consider a more conservative budget projection based on an extrapolation of the President’s FY2011 budget submission that projects roughly $700 million less funding, or $3.0 billion available over the decade. In the event that insufficient funds are available to carry out the recommended program, the first priority is to develop, launch, and operate WFIRST and to implement the Explorer program and core research program recommended augmentations. The second priority is to pursue the New Worlds Technology Development Program, as recommended, to mid-decade review by a decadal survey implementation advisory committee (as discussed in Chapter 3), to start LISA as soon as possible subject to the conditions discussed above, and to invest in IXO
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New Worlds, New Horizons in Astronomy and Astrophysics FIGURE 7.12 Astro2010-recommended program for NASA—example phasing. This sandchart is the outcome of a committee exercise carried out in FY2010 dollars to show that the phased program recommended would fit within the budget constraints adopted by the committee in developing its recommendations. The profiles and budget costs will vary on a project-by-project and program-by-program basis and should not be taken as representing a literal recommended program. The sandcharts are presented here to show, as an existence proof, that within a budget that is flat for the decade in FY2010 dollars the Astro2010-recommended new initiatives and program augmentations are implementable within NASA SMD spending limits. technology development as recommended. The third priority is to pursue the CMB Technology Development Program, as recommended, to mid-decade review by a decadal survey implementation advisory committee. It is unfortunate that this reduced budget scenario would not permit participation in the JAXA-SPICA mission unless that mission’s development phase is delayed. NSF Astronomy The proposed program for NSF has been constrained to fit within an NSF-AST budget doubling scenario, in which $500 million becomes available by 2021 for new activities and the annual NSF-AST budget rises to $325 million. As the example presented in Figure 7.13 shows, it is possible to fund early operations for LSST beginning in 2016, build up the Mid-Scale Innovations Program augmentation,
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New Worlds, New Horizons in Astronomy and Astrophysics FIGURE 7.13 Astro2010-recommended program for NSF—example phasing. This sandchart is the outcome of a committee exercise carried out in FY2010 dollars to show that the phased program recommended would fit within the budget constraints adopted by the committee in developing its recommendations. The profiles and budget costs will vary on a project-by-project and program-by-program basis and should not be taken as representing a literal recommended program. The sand-charts are presented here to show, as an existence proof, that within a “doubling” budget over the decade the Astro2010-recommended new initiatives and program augmentations are implementable within NSF-AST spending limits. complete CCAT, augment the core research program, and collaborate on ACTA. The timescale for starting to operate GSMT is quite uncertain, but this option can also be accommodated toward the end of the decade. As regards the sequencing of LSST and GSMT, in this and the two budget scenarios that follow, it is assumed that LSST would enter the MREFC process as soon as the budgets would allow and that GSMT would follow. In the event that the realized budget is closer to an extrapolation of the president’s FY2011 budget, that is, between the optimistic budget-doubling and the pessimistic flat-budget scenarios, the order of priority is to phase in the recommended core research program augmentations and the Mid-Scale Innovations Program together and at as fast a rate as the budget will allow, noting that the recommended Gemini augmentation is time-critical. LSST would receive an MREFC start and require NSF-AST operations funding beginning in 2016. NSF-AST sup-
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New Worlds, New Horizons in Astronomy and Astrophysics port for GSMT operations and ACTA collaboration both would be delayed until funding becomes available. If the realized budget is truly flat in FY2010 dollars, the implication is that, given the obligation to provide operational costs for the forthcoming ALMA and ATST, there is no possibility of implementing any of the recommended program this decade—without achieving significant savings through enacting the recommendations of the first 2006 senior review process and/or implementing a second more drastic senior review before mid-decade. Because the termination of programs takes time to implement in practice, it will be difficult to accrue significant new savings before the end of the decade. Thus, in practice, very few new activities could be started within NSF-AST. DOE High Energy Physics A program fitted under the DOE budget doubling scenario means that roughly $40 million per year would be available by the end of the decade, after due allowance for an underground dark matter detection program as recommended by HEPAP-PASAG. As indicated by the example shown in Figure 7.14, this amount will be sufficient to allow participation in LSST, WFIRST, and ACTA as well as some of the smaller astrophysical initiatives recommended by HEPAP-PASAG under Scenario C. In addition, a $2 million per year Theory and Computation Networks program is recommended. However, if the budget is lower, the HEPAP-PASAG recommended investment in dark matter detection will be reduced and the available funds will decrease to $15 million under Scenario A. DOE is a minor partner in the two largest projects that the survey committee has recommended—LSST and WFIRST—and it is likely that the phasing will involve choices by NSF and NASA, respectively. Other considerations being equal, the recommended priority order is to collaborate first on LSST because DOE will have a larger fractional participation in that project, and its technical contribution is thought to be relatively more critical. ACTA, Theory and Computation Networks, and the smaller initiatives have lower priority. EPILOGUE This is an extraordinary time in astronomy. The scientific opportunities are without precedent—finding and characterizing other planets like Earth, tracing the history of the cosmos from the time of inflation to our own galaxy and solar system today, detecting the collisions of black holes across the universe, and testing the implications of Einstein’s theories a century after they were formulated. The tools are becoming available to make giant strides toward deciphering the mysteries of the two primary components of the cosmos—dark energy and dark matter—and
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New Worlds, New Horizons in Astronomy and Astrophysics FIGURE 7.14 Astro2010-recommended program for DOE—example phasing. This sandchart is the outcome of a committee exercise carried out in FY2010 dollars to show that the phased program recommended would fit within the budget constraints adopted by the committee in developing its recommendations. The profiles and budget costs will vary on a project-by-project and program-by-program basis and should not be taken as representing a literal recommended program. The sandcharts are presented here to show, as an existence proof, that within a “doubling” budget over the decade the Astro2010-recommended new initiatives and program augmentations are implementable within DOE High Energy Physics spending limits. toward discovering the prevalence of life in the universe. The discoveries that will be made will profoundly change our view of the cosmos and our place within it. Astronomy, ever young, is vibrant and currently growing by attracting enthusiastic and skilled newcomers from other fields—particle physics, biology, chemistry, computer science, and nuclear physics—and traditional astronomers’ professional horizons are enlarged by learning from them. This is truly a privileged time to be an astronomer. Changes are apparent now in the way research is being done. It is more ambitious. And it is also more collaborative and more international, which enlarges the realm of what is achievable. This context complicates the task of preparing a strategic vision and necessitates a new fiscal, technical, and temporal realism at a time of constrained economic resources in the United States that will inevitably lead to a smaller fraction of the global research effort supported by the federal government.
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New Worlds, New Horizons in Astronomy and Astrophysics The committee has been strategic in its thinking, crafting a program that optimizes the scientific return, building on previous public investment in astrophysics while making difficult choices in laying a foundation for the next decade. The committee notes the unprecedented level of effort and involvement in this survey by the astronomical community, with hundreds of astronomers and astrophysicists attending town hall meetings, contributing white papers, and serving on panels. The vision put forth in this report is a shared vision.