Optimizing the U.S. Ground-Based Optical and Infrared Astronomy System (2015)

4
Pursuing the Science in the LSST and GSMT Era

4.1 SCIENCE-DRIVEN NEEDS FOR OIR INSTRUMENT CAPABILITIES

Transformative studies in key science areas, from planets and exoplanets, to stellar and galaxy evolution, to dark energy large-scale cosmology, will require specialized instrumentation and technology development as well as substantial increases in collecting area and/or field of view. New Worlds, New Horizons in Astronomy and Astrophysics¹ (NWNH), the Portfolio Review Committee (PRC) report,² and Vision and Voyages for Planetary Science in the Decade 2013-2022³ (VVPS) provide extensive discussions of critical high-priority questions and the instrumentation needed to answer them. This section summarizes some of the key capabilities that will be needed in the coming years to address different areas of research as the Large Synoptic Survey Telescope (LSST) and the Giant Segmented Mirror Telescopes (GSMTs) come online.

Wide-field, moderate-resolution, highly multiplexed spectrographs were highlighted in NWNH as synergistic instruments for LSST and Wide-Field Infrared Sur-

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¹ National Research Council (NRC), 2010, New Worlds, New Horizons in Astronomy and Astrophysics, The National Academies Press, Washington, D.C., p. 79.

² National Science Foundation (NSF), 2012, Advancing Astronomy in the Coming Decade: Opportunities and Challenges. Report of the National Science Foundation Division of Astronomical Sciences Portfolio Review Committee, http://www.nsf.gov/mps/ast/portfolioreview/reports/ast_portfolio_review_report.pdf.

³ NRC, 2011, Vision and Voyages for Planetary Science in the Decade 2013-2022. The National Academies Press, Washington, D.C.

vey Telescope (WFIRST) measurements of cosmic acceleration, and in the NWNH report of the Panel on Optical and Infrared Astronomy from the Ground⁴ as versatile instruments on 4- to 8-meter telescopes for a large range of science drivers in four of the five science frontier panels (Cosmology and Fundamental Physics, Galactic Neighborhood, Galaxies Across Cosmic Time, and Stars and Stellar Evolution). In 2011, the National Optical Astronomical Observatory (NOAO) hosted a community workshop to explore in detail the science that could be achieved with BigBOSS,⁵ now known as DESI,⁶ which is a wide-field (3-degree-diameter) massively multiplexed (up to 5,000 targets per field) fiber-fed spectrograph. There are a number of other highly multiplexed spectrographs in development for 4- to 8-meter-class telescopes, which are not public access or are non-U.S., as detailed in Section 5.1. Such spectrographs and related integral field unit (IFU) systems will allow surveys of millions of galaxies at redshifts z > 1. These measurements will be crucial cosmological probes that provide insight into dark energy and the distribution of dark matter as well as study galaxy evolution and primordial star formation. These spectrographs are also critical for surveying large samples of Milky Way stars to understand the chemical evolution of the galaxy as well as nearby galaxies by providing precise elemental abundances. They will enable studies of the kinematics and dynamical evolution of the Milky Way and nearby galaxies. Gaia results will motivate further science cases. Community access to such a spectrograph would open up more possibilities for key high-impact science.⁷ Further discussion and a recommendation for a wide-field, massively multiplexed spectrograph in the Southern Hemisphere is given in Section 5.1.

High-throughput, moderate resolution optical and near-IR spectrographs and spectropolarimeters on large and giant telescopes will be critical for a variety of observations, including transients (see discussion of LSST follow-up in Section 5.1 and a recommendation in Section 5.2), quasars, planetary atmospheres, individual objects such as stars, binaries, and galaxies measured in statistical samples, and individual objects studied as part of multi-wavelength campaigns.

High-contrast imaging and spectroscopy on large and GSMT-class telescopes will be necessary to map the structure and evolution of protoplanetary disks.

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⁴ NRC, 2011, Panel Reports—New Worlds, New Horizons in Astronomy and Astrophysics, The National Academies Press, Washington, D.C., p. 353.

⁵ National Optical Astronomy Observatory (NOAO), “Highly Mutiplexed Spectroscopy with BigBOSS on the Mayall Telescope: An NOAO Community Workshop,” http://www.noao.edu/meetings/bigboss/, accessed February 1, 2015.

⁶ Acronyms, especially those denoting individual instruments and missions, are defined in Appendix C.

⁷ G. Rudnick, A. Myers, C. Badenes, T. Beers, S. Brittain, J. Carlin, D. Cinabro, M. Cooper, A. Connolly, E. Ellingson, X. Fan, et al., 2014, “The Need for Community Access to Highly Multiplexed Spectroscopy: DESI Availability in the Age of LSST,” white paper submitted to the committee.

These capabilities will also provide details of the surfaces, atmospheres, and rings of solar system planets as well as small bodies in the solar system. The advent of giant telescopes along with adaptive optics (AO) coronagraphy offers the tantalizing prospect of direct imaging of Jupiter analogs around nearby solar-type stars. Large-aperture OIR telescopes help constrain parameters involved in most stellar processes, such as the formation and evolution of stars, characterizing the initial mass function, the effect of stellar duplicity, the influence of magnetic fields, mass loss, rotation, and the phenomena of supernova and gamma ray bursts. Further gains will be achieved through high-sensitivity, high-resolution imaging, spectroscopy, and spectropolarimetry on AO-equipped 6-meter and larger telescopes that can probe intrinsically fainter, more distant, and more varied targets. Studies of the structure of high-redshift galaxies with near-infrared (IR) AO instruments on large telescopes will complement ALMA observations of their gas content to provide insight on galaxy evolution and star formation processes. See Section 4.2 for more discussion and a recommendation on AO technology development.

The next generation of telescopes will extend observations to more crowded environments and much greater distances than current facilities. The light-gathering power of a 30-meter-class telescope at low-background, near-IR wavelengths is such that an AO-assisted spectroscopic performance at moderate resolution will significantly exceed that of the James Webb Space Telescope (JWST), in particular for compact sources, while an AO-fed IFU spectrograph will reveal galaxy structures, kinematics, and metallicities. High-resolution multi-object spectroscopy on large telescopes will further research in the field of galactic archaeology to probe the chemical composition of disk, bulge, and halo stars⁸ and to survey star-forming molecular clouds in the Milky Way Galaxy to address the factors governing the initial mass function and the rates and efficiencies of star formation.⁹ These spectroscopic capabilities enable studies of the topology, ionization state, and chemical enrichment of the intergalactic medium and the first galaxies at the end of the cosmic dark ages. As a result, near-IR spectroscopy on an AO-assisted 30-meter-class telescope will provide a detailed story of the properties and influence of the first stars and black holes on the intergalactic medium.

On galaxy scales, basic questions center on feedback mechanisms that affect star formation, energy transport in the interstellar medium, and metal enrichment, as well as the relationship between star formation history, supermassive black hole growth, and dark matter halos. These interrelations will help in understanding the formation and evolution of galaxies. Such studies are enabled at both low and high redshift by spectroscopic observations of rest-frame near-ultraviolet and optical

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⁸ M. Rich, 2014, white paper submitted to the committee.

⁹ S.T. Megeath, 2014, “O/IR Capabilities and the Study of Star Formation in the Nearest 2 kpc,” white paper submitted to the committee.

interstellar lines, dynamical measurements, high-angular-resolution imaging, and OIR photometry.

Polarimetry across a broad spectral range is important for characterizing magnetic fields to understand their role in active galactic nuclei (AGN), proto-stellar disks, cosmic ray propagation, energy transport in star-forming regions, and large-scale polarized dust emission that affects cosmic microwave background radiation.¹⁰ In addition, development of OIR interferometry techniques would advance the understanding of exozodiacal and protoplanetary disks and the effect of magnetic fields on stars.¹¹ Extreme precision Doppler spectroscopy for radial velocity measurements by special-purpose instruments will be critical to exoplanet studies; see Section 4.2 for further discussion and a recommendation in this regard.

OIR astronomy will also remain critically important in the quest to determine cosmological initial conditions over the widest possible dynamic range, through observations of large-scale structure (using galaxies, intergalactic gas, and gravitational lensing) and of standard candles (primarily Type Ia supernovae). Large, ground-based optical imaging surveys such as LSST (described further in Section 4.4) will provide high signal-to-noise data for billions of galaxies.

Some pivotal instruments for future science are already in operation, such as wide-field optical and IR multi-object spectrographs and imagers; high-dispersion spectrographs; and AO systems on Gemini, LBT, MMT, Magellan, HET, and Keck. First generation instruments planned for TMT and GMT will include many of these decadal priority instruments, except for high-contrast optical and mid-IR AO imagers¹² and wide-field multiplexed spectrographs. These capabilities, combined with the significant increase in collecting area, will undoubtedly result in unprecedented and unimagined new scientific advances. Public access to large telescopes with these critical instrument capabilities (some of which already exist, such as high-resolution echelle optical spectrographs) is and will continue to be important to the community.¹³

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¹⁰ B.-G. Andersson, A. Adamson, K.S. Bjorkman, J.E. Chiar, D.P. Clemens, D.C. Hines, J.L. Hoffman, T.J. Jones, A. Lazarian, C. Packham, J.E. Vaillancourt, et al., 2014, “The Need for General-Use Polarimeters in the Era of LSST,” white paper submitted to the committee.

¹¹ J.T. Armstrong, M.J. Creech-Eakman, J.D. Monnier, S.T. Ridgway, T.A. ten Brummelaar, and G.T. van Belle, 2014, “Supporting Community Access to Optical/Infrared Interferometry,” white paper submitted to the committee.

¹²Section 4.3; R.A. Bernstein, G. Jacoby, P. McCarthy, et al., 2014, “Instrumentation and Technical Excellence in Astronomy in the LSST and ELT Era,” white paper submitted to the committee.

¹³ I.U. Roederer, 2014, white paper submitted to the committee.

In addition to large and extremely large telescopes, small (≤ 3-meter) and medium (3.5- to 5-meter) telescopes will continue to play an important role in many areas of science,¹⁴ even if most are at non-federal observatories. Gaia and TESS are two satellites that will generate significant follow-up opportunities. LSST’s catalog will include millions of objects near its bright end limits that are still accessible with small-aperture telescopes for imaging with a different cadence than LSST, and spectroscopy, spectropolarimetry, deeper observations, narrowband imaging, or near-IR imaging, which are not possible with LSST. Such targets include, for example, T Tauri variable stars, novae and supernovae, AGNs that vary on timescales of hours, emission lines from planetary nebulae, star-forming regions, and starburst galaxies.

The PRC report,¹⁵ NWNH,¹⁶ and VVPS¹⁷ assessed the OIR instrument needs of the community based on the science priorities and related key questions. Table 4.1 summarizes many critical capabilities needed in the coming years and some of the science that will be enabled by them. The list is not in priority order; some entries have recommendations in subsequent sections.

4.2 TECHNOLOGY DEVELOPMENT

Technology development continues to drive observational progress in OIR astronomy. Robust investment in technology development is essential to ensure that astronomical advances continue and that future breakthrough instruments are developed, as emphasized in the NWNH OIR panel report, VVPS, and in previous

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¹⁴ See the white papers submitted to the committee: S. Heathcote, 2014, “Cerro Tololo Inter-American Observatory in the LSST Era”; J.M. Strader, E.F. Brown, L. Chomiuk, E.D. Loh, and S.E. Zepf, 2014, “A View of Astronomy at Universities in the LSST Era.”

¹⁵ NSF, 2012, Advancing Astronomy in the Coming Decade: Opportunities and Challenges. Report of the National Science Foundation Division of Astronomical Sciences Portfolio Review Committee, http://www.nsf.gov/mps/ast/portfolioreview/reports/ast_portfolio_review_report.pdf.

¹⁶ NRC, 2011, Panel Reports—New Worlds, New Horizons, Table 7.1.

¹⁷ NRC, 2011, Vision and Voyages for Planetary Science, Table 10.1.

TABLE 4.1 Key Instrument Needs in the Era of the Large Synoptic Survey Telescope (LSST)

sections of this report.¹⁸ Several key areas for continued technology development highlighted in NWNH were adaptive optics (also in VVPS), precision radial velocities, and astronomical detectors. There is a widespread sense that the United States has fallen behind other countries in technology development and that innovation, while not stalled, is eroding.

AO has now become a foundational technology on most large ground-based telescopes (e.g., the Keck, Gemini, MMT, Magellan), enabling diffraction-limited, near-IR imaging and spectroscopy that rivals and even surpasses that from space (see Figure 4.1). No longer thought of as follow-up technology to be implemented merely as an add-on, AO is now integrated into modern telescope system and instrumentation design from the beginning.

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¹⁸ See also the following AO presentations to the committee on October 12, 2014: Claire Max, University of California Observatories/UC Santa Cruz, “The Status of AO Worldwide”; Phil Hinz, University of Arizona, “The Role of Adaptive Optics—with Examples”; and Richard Dekany, California Institute of Technology (available at http://sites.nationalacademies.org/BPA/BPA_087934#presentations).

FIGURE 4.1 Top row: Images of five gravitational lens systems obtained with Hubble Space Telescope (HST)/Near Infrared Camera and Multi-Object Spectrometer (NICMOS) in the H band. The object in the center of each image is the foreground lensing galaxy. The background galaxy is lensed into arcs or a ring, and sometimes has multiple images of its central active galactic nuclei. Bottom row: Keck adaptive optics (AO) images of the same systems obtained with Near Infrared Camera 2 in the Kp band. The AO images are noticeably sharper than the HST images. SOURCE: Courtesy of Professor Chris Fassnacht (University of California, Davis).

AO techniques traditionally have been best suited for detailed study of individual objects, achieving the highest spatial resolution for resolved objects, crowded fields, and high contrast, and for obtaining the greatest sensitivity for spectroscopy on large apertures. Maturation of technologies developed over the past 20 years, and continuing today, shows emerging capability for other applications, which in the future may even include wide-field imaging and highly multiplexed resolved-object spectroscopy. To achieve the current precision of AO, key developments have been made in the production of stable lasers, large-format deformable mirrors, and lower-noise wavefront sensors. Adaptive Secondary Mirrors (ASM) have dramatically changed the scope and power of AO in the past few years. An ASM can allow any telescope a wide field of view (FOV) at 0.2-0.3 arcsecond resolution in the near-IR (1-3 microns),¹⁹ and coupling an ASM with the sensitive wavefront sensor

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¹⁹ See, for example, the GLAO prototype at the MMT (M. Hart, N.M. Milton, C. Baranec, K. Powell, T. Stalcup, D. McCarthy, C. Kulesa, and E. Bendek, 2010, A ground-layer adaptive optics system with multiple laser guide stars, Nature 466(7307):727-729).

at the Magellan Telescope has enabled the first visible wavelength AO science.²⁰ An ASM is being deployed on the Very Large Telescope (VLT) and designed for several of the next generation of giant telescopes.

Going forward, many aspects of NWNH and VVPS science need robust AO capabilities across wavelengths, spectral resolution, and cadence.²¹ The growing science impact of AO today is the result of previous investments, which peaked in the mid-2000s under the Adaptive Optics Development Program (AODP) at just short of $20 million per year but have now fallen to less than one-fifth of that.²² Optimized usage of current and next-generation large apertures relies on continuing investment channels for this high-payoff (albeit expensive) area of technology development. The AO required for the next-generation large-aperture telescopes is a significant extension of today’s state-of-the-art technology.²³ At the same time, clever application of AO techniques to smaller apertures²⁴ can create unique roles for these facilities also operating at their full spatial resolution and sensitivity.

Dedicated exoplanet-detecting instruments, from high-contrast AO coronagraphs on ground-based telescopes to IR Doppler spectrographs for high-precision radial-velocity measurements, will be crucial to provide characterization of these systems. Combining these observations with synoptic studies and space-based observations will elucidate how planetary systems form and whether systems like the solar system are common or rare. Specifically in the field of precision radial velocity for exoplanet detection, the Europeans have been investing in new technology for the past decade; the United States is not keeping up.

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²⁰ L.M. Close, J.R. Males, K. Morzinski, D. Kopon, K. Follette, T.J. Rodigas, P. Hinz, Y.-L. Wu, A. Puglisi, S. Esposito, A. Riccardi, et al., 2013, Diffraction-limited visible light images of orion trapezium cluster with the Magellan adaptive secondary adaptive optics system (MagAO), The Astrophysical Journal 774(2):94.

²¹ NRC, 2011, Panel Reports—New Worlds, New Horizons, Table 7.3.

²² Association of Universities for Research in Astronomy, Coordinating Council of Observatory Research Directors, 2008, A Roadmap for the Development of United States Astronomical Adaptive Optics, http://www.aura-astronomy.org/news/AO_Roadmap2008_Final.pdf.

²³ See white paper by Monnier highlighting the need for more AO development (J.D. Monnier, J.T. Armstrong, M.J. Creech-Eakman, S.T. Ridgway, T.A. ten Brummelaar, and G.T. van Belle, 2014, “Funding Technology Development and Novel Instrumentation Today in Order to Enable Breakthrough Observing Techniques Tomorrow,” white paper submitted to the committee) and the presentations to the committee on October 12, 2014, by Claire Max and by Phil Hinz (Claire Max, University of California Observatories/UC Santa Cruz, “The Status of AO Worldwide”; Phil Hinz, University of Arizona, “The Role of Adaptive Optics—with Examples” (both available at http://sites.nationalacademies.org/BPA/BPA_087934#presentations).

²⁴ For example, Robo-AO does large-scale surveys robotically at the Palomar 60″. It has been used for exoplanet confirmations of Kepler candidates as well as observations of massive storms on Uranus (University of Hawaii, Institute for Astronomy, “Robo-AO: Autonomous Laser-Adaptive-Optics for Few Meter Class Telescopes,” http://www.ifa.hawaii.edu/Robo-AO/, accessed February 1, 2015).

In the newly formed NN-EXPLORE (NASA-NSF Exoplanet Observational Research) partnership to support precision radial velocities,²⁵ the National Science Foundation (NSF) will provide facility support on the 3.5-meter WIYN telescope and NASA will provide funding to build an Extreme Precision Doppler Spectrometer (EPDS). This partnership was designed to meet the recommendations of NWNH that “NASA and NSF should support an aggressive program of ground-based, high-precision, radial-velocity surveys of nearby stars in order to validate and characterize exoplanet candidates.”²⁶ This partnership should prove to be a valuable addition for the community, and the committee applauds the willingness of NSF and NASA to coordinate activities in a way that responds to long-standing community input and maximizes productivity and ground-based OIR community access.²⁷

NASA’s announcement of intent for the instrument sets a requirement of 50 cm/s precision and a goal of 10 cm/s. Before Earth-like masses can be reliably detected, nightly stellar noise of the order of 100 cm/s in the most stable stars²⁸ must be overcome and 10 cm/s precision must become the state of the art rather than merely a goal. A deliberate development program improving wavelength calibration and detector technology is needed, in parallel with analytic efforts to overcome stellar noise.²⁹

Detector technology has evolved over the past 20 years, with larger sizes and greater sensitivities over larger wavelength ranges. Wide-field imaging and massively multiplexed spectrographs are possible because of the development of detectors with mosaics of hundreds of millions of pixels, as highlighted in NWNH. The community relies on a small number of experts to build and tune charge-coupled device controllers. In the infrared, the number of vendors with high-quality, low-noise, 1-5 micron detectors has declined considerably. Since astronomy is generally a photon-starved science, the development of superconducting single-photon broadband detectors would help to advance heterodyne detection and resolution of narrow astronomical lines, fringes in interferometry, and wavefront sensing

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²⁵ L. Allen and D. Silva, 2014, “KPNO in the Next Decade and Beyond,” white paper submitted to the committee.

²⁶ NRC, 2010, New Worlds, New Horizons, p. 20.

²⁷ Although agreed on by the agencies and announced as this committee was deliberating, the proposed radial velocity instrument is an example of a partnership that in the future can be held to the standard described in Chapter 6, with an eye toward building instrumentation that optimizes the entire U.S. System.

²⁸ F. Pepe, C. Lovis, D. Ségransan, W. Benz, F. Bouchy, X. Dumusque, M. Mayor, D. Queloz, N.C. Santos, and S. Udry, 2011, The HARPS search for Earth-like planets in the habitable zone, Astronomy and Astrophysics 534(A58):1-16.

²⁹ For a planned workshop in this regard, see “The Second Workshop: Extreme Precision Radial Velocities” (http://exoplanets.astro.yale.edu/workshop/EPRV/Home.html, accessed February 1, 2015).

for adaptive optics. MKID (microwave kinetic inductance detectors), detectors made with superconducting material that would allow very precise measurements of the frequency of incoming photons, are beginning to be incorporated in OIR instruments.³⁰

In addition to the technology endeavors highlighted above, future technological development in, for example, optical interferometry, next-generation detectors, astro-photonics, lightweight mirrors, and fiber positioners will be key to achieving decadal science. Determining these technical priorities would be a logical part of the community’s system strategic planning process (see Section 6.3), with implementation supported by funding streams within NSF (MSIP, ATI, and MRI as appropriate) and NASA and Department of Energy (DOE) technology programs.

Pushing the frontiers requires supporting a range of innovative projects from ALMA and LSST to small grants for basic exploratory research. The existing ATI program in principle supports the small, simpler, and faster programs to advance technology and to train the next generation of instrument builders. As stated in NWNH, while the technology itself is important, it is vital that sufficient support for the development and strengthening of the technology workforce be part of these technology efforts as well (see Section 3.5). A desirable by-product of investment in technology development is the creation of more robust opportunities to train the next generation of instrumentalists. If NSF does not maintain strong support for the infrastructure needed for innovation, basic science, and training of the next generation, the United States will fail to lead in the technology development that is critical for scientific discovery.

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³⁰ See, for example, the Array Camera for Optical to Near-IR Spectrophotometry (ARCONS) instrument (B.A. Mazin, S.R. Meeker, M.J. Strader, P. Szypryt, D. Marsden, J.C. van Eyken, G.E. Duggan, A.B. Walter, G. Ulbricht, and M. Johnson, 2013, ARCONS: A 2024 pixel optical through near-IR cryogenic imaging spectrophotometer, Publications of the Astronomical Society of the Pacific 125(933):1348-1361).

4.3 IMPORTANCE OF THE GIANT SEGMENTED MIRROR TELESCOPES

GSMTs are being developed privately by two consortia based in the United States: TMT at Maunakea, expected to have first light in 2024, and the 24.5-meter GMT at Carnegie’s Las Campanas Observatory in Chile, expected to have first light in 2021 (both shown in Figure 4.2). The advent of these two GSMTs, along with European Southern Observatory’s 39-meter European Extremely Large Telescope (E-ELT), will revolutionize OIR astronomy by achieving angular resolution and depth far beyond current telescopes. The GSMTs will contribute critically to addressing the majority of the next decade’s principal science questions³¹ and are required for five key science programs in NWNH, including the direct detection of giant exoplanets and the precise characterization of the Milky Way’s central black hole, environments and progenitors of supernovae and gamma ray bursts (GRBs), dark matter halos, and physical properties of the first stars.³² VVPS highlights GSMTs for future solar system observations such as thermal emission from Neptune and compositional measurements of trans-Neptunian objects.

The most progress will come from combined studies at many different wavelengths using both ground-based and space-based facilities, as mentioned in Chapter 2. This essential synergy was clearly demonstrated by the combination of HST and the Blanco 4-meter, Gemini 8-meter, and Keck 10-meter telescopes for many significant discoveries, most notably the accelerating universe. Similarly, the TMT and GMT will be critical complements to major new facilities, including LSST, ALMA, JWST, Gaia, WFIRST, and Euclid.

The TMT and GMT will provide these synergistic capabilities through advanced adaptive optics and powerful first-light science instruments, including optical and near-infrared high-resolution spectrographs, moderate-resolution multi-object spectrographs, and imagers. In addition, since sensitivity increases in proportion to the fourth power of diameter for diffraction-limited point sources, a 30-meter telescope will be over 80 times more sensitive than a 10-meter telescope for some projects. Moderately large fields of view will facilitate, among other efforts, the deployment of multi-object spectrographs that will be critical to many areas of science (see Sections 4.1 and 5.1).

NSF and the TMT Observatory Corporation signed a cooperative agreement in 2013 initiating a 5-year planning study to examine potential models for NSF participation in TMT for the benefit of the U.S. astronomical community. NOAO is leading TMT participation planning activities under the cooperative agreement, engaging the U.S. astronomical community, and it has established a U.S. TMT Liaison office and a U.S. TMT Science Working Group. This planning effort will

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³¹ NRC, 2011, Panel Reports—New Worlds, New Horizons, Table 7.1.

³² NRC, 2011, Panel Reports—New Worlds, New Horizons, Table 7.2.

FIGURE 4.2 Conceptual sketches of the Thirty Meter Telescope (top) and Giant Magellan Telescope (bottom). SOURCE: (Top) Courtesy of TMT International Observatory; (bottom) Courtesy of Giant Magellan Telescope, GMTO Corporation.

lead to a set of reports based on input solicited from the scientific community that will constitute a plan with options for possible U.S. participation in TMT. The TMT Science Working Group notes several ways in which the scientific return from federal investment in TMT might be maximized, including public access to archived data, public participation in key science programs, and contributions by university groups to second-generation instruments. When the TMT International Observatory (TIO) was legally incorporated, AURA became an associate in TIO and delegated NOAO to execute AURA’s associate member responsibilities on behalf of the U.S. astronomical community.

The GMT partners³³ have indicated a willingness to entertain new partners and have extended membership on their Scientific Advisory Committee to members of the U.S. astronomical community who are not associated with partner institutions. The Giant Magellan Telescope Organization Board³⁴ and the GMT Science Advisory Committee³⁵ are open to a variety of mechanisms for community participation in return for federal support, including open peer-reviewed access, open community participation in Key Projects, and partnering with NSF and non-member institutions to develop second-generation instrumentation and AO technology.³⁶

NWNH recommended that “due to severe budget limitations, a federal partnership in a GSMT will be limited to a minority role in one project”³⁷ and recommended a 25 percent share in a GSMT as a goal, either through Major Research Equipment and Facilities Construction (MREFC) funds or operations costs, as a formal partner. VVPS endorsed the NWNH recommendations and support for the GSMTs. As of the writing of this report, the two GSMT projects (GMT and TMT) appear to be moving toward construction. Even though the current funding situation does not allow substantial involvement in the GSMT projects by NSF beyond the 5-year agreement with TMT, the committee underscores the importance of

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³³ The GMT consortium includes participation by Carnegie Observatories, the University of Texas at Austin, Texas A&M, the University of Arizona, the University of Chicago, Harvard University, and the Smithsonian Astrophysical Observatory. International partners include Australia, Korea, and Brazil.

³⁴ W.L. Freedman, E. Moses, C. Alcock, T. Armandroff, M. Colless, W. Couch, D. DePoy, R. Franzen, L. Hicke, B. Jannuzi, R. Kirshner, R. Kolb, et al., 2014, “Community Access to the GMT in the Era of LSST,” white paper submitted to the committee.

³⁵ R.G. Kron, E. Berger, R. Blum, H.W. Chen, A. Cochran, J. Crane, G. Da Costa, J. Dalcanton, M. Donahue, J. Eisner, D. Fabricant, J.-J. Lee, et al., 2014, “The Role of GMT in the OIR System in the LSST Era,” white paper submitted to the committee.

³⁶ See Patrick McCarthy, Giant Magellan Telescope, “GMT and the OIR System in the Era of the LSST,” presentation to the committee on October 12, 2014, http://sites.nationalacademies.org/cs/groups/bpasite/documents/webpage/bpa_090096.pdf.

³⁷ NRC, 2010, New Worlds, New Horizons in Astronomy and Astrophysics, p. 231.

community involvement in the future.³⁸ There are a number of ways that this could occur at a federal participation level at or below that recommended in NWNH. It would be prudent for NSF to plan to enable broader access by preparing for the possibility of engagement with either or both of the projects—for example, through shared operations costs, instrument development, exchange partnerships (see Chapter 6), or partnership in science projects. These options could be pursued in the event that NSF receives more funding, or by trading off other facilities and programs.

4.4 THE LARGE SYNOPTIC SURVEY TELESCOPE

LSST is the top-ranked large ground-based project in NWNH, and also highly ranked in VVPS. It will be an 8.4-meter telescope designed for wide-field imaging, with a 9.6 square degree FOV (see Figure 4.3). It is being built through a public-private partnership, with federal support from NSF and DOE and broad private

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³⁸ The U.S. TMT Science Working Group surveyed U.S. astronomers about TMT priorities. Of the 467 respondents, 68% favored a partnership share in TMT of at least 15% for the U.S. community beyond the current partners (M. Dickinson, 2015, Recent developments with the Thirty Meter Telescope, NOAO Newsletter, March 2015, https://www.noao.edu/noao/noaonews/mar15/pdf/111syssci.pdf).

FIGURE 4.3 Conceptual sketch of the Large Synoptic Survey Telescope. SOURCE: Courtesy of Large Synoptic Survey Telescope Corp.

and international support.³⁹ It has entered the NSF MREFC funding line for construction, the M1M3 mirror is nearing completion, and the camera team has just

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³⁹ Institutional members are Adler Planetarium, Argonne National Laboratory, Brookhaven National Laboratory (BNL), California Institute of Technology, Carnegie Mellon University, Chile, Columbia University, Cornell University, Drexel University, Fermi National Accelerator Laboratory, George Mason University, Google, Inc., Harvard-Smithsonian Center for Astrophysics, Institut de Physique Nucleaire et de Physique des Particules (IN2P3), Johns Hopkins University, Kavli Institute for Particle Astrophysics and Cosmology (KIPAC)-Stanford University, Las Cumbres Observatory Global Telescope Network, Inc., Lawrence Livermore National Laboratory (LLNL), Los Alamos National Laboratory (LANL), National Optical Astronomy Observatory (founding member), Northwestern University, Princeton University, Purdue University, Research Corporation for Science Advancement (founding member), Rutgers University, SLAC National Accelerator Laboratory, Space Telescope Science Institute, Texas A & M University, The Institute of Physics of the Academy of Sciences of the Czech Republic (affiliate), Pennsylvania State University, University of Arizona (founding member), University of California, Davis, University of Illinois, Urbana-Champaign, University of Michigan, University of Oxford, University of Pennsylvania, University of Pittsburgh, University of Washington (founding member), Vanderbilt University, and Fisk University.

successfully completed a DOE Critical Decision (CD-2) Review. LSST will survey the southern sky over 20,000 square degrees in six ultraviolet and optical through near-IR bands (0.3-1.1 microns) to a final depth of r = 27.5 mag, visiting each field about 1,000 times during its planned 10-year project lifetime.

The design of LSST makes it useful for a wide range of astronomical studies. LSST will detect about 10 billion stars in the Milky Way and nearby galaxies that will provide information about the structure of galaxy disk and halo components. Transient events such as supernovae, optical counterparts of GRBs, AGNs, periodic variable stars, Kuiper Belt objects, and near-Earth asteroids will be probed in the time domain. Statistical studies of galaxies will be aided by observations of about 3 billion galaxies, the distributions of which will be used to understand dark matter on large scales through gravitational lensing, and the data will allow studies of dark energy through supernovae, weak gravitational lensing, clusters of galaxies, and baryon acoustic oscillations. A wide range of key science questions in the decadal priority lists will be impacted when LSST comes online.

LSST science requirements were defined by considering the needs of four broad areas: dark energy, solar system, optical transients, and galactic structure. The fact that the LSST Science Book⁴⁰ is more than 500 pages long, detailing science programs from the solar system to stellar populations, the Milky Way, nearby galaxies, transients, distant galaxies, AGNs, supernovae, lensing, dark matter, and large scale structure, underscores the critical role of LSST in enabling the astronomical community to tackle a wide variety of astronomical questions when it comes online. Its massive public archive will stimulate worldwide investigations. Although a key project is the dark energy part of the survey, which is a self-contained project with Level 3 support from DOE through the Dark Energy Survey Collaboration (DESC), there is no doubt that the cadenced observations of billions of stars and galaxies as well as solar system objects will drive enhanced science benefits from follow-up observations using complementary facilities.

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⁴⁰ Large Synoptic Survey Telescope Corp., 2009, Large Synoptic Survey Telescope Science Book Version 2.0. November, http://www.lsst.org/lsst/science/scibook.