Summary
We live in an extraordinary period of discovery in astronomy and astrophysics. Six Nobel Prizes have been awarded over the past decade alone for discoveries based on astronomical data (dark energy, gravitational waves, neutrino oscillations, the discovery of exoplanets, cosmology, and supermassive black holes). Many of the ambitious scientific visions of the 2010 New Worlds, New Horizons (Astro2010)1 decadal survey are being fulfilled, but momentum has only grown. We stand on the threshold of new endeavors that will transform not only our understanding of the universe and the processes and physical paradigms that govern it but also humanity’s place in it.
This report of the Committee for a Decadal Survey on Astronomy and Astrophysics 2020 (Astro2020) proposes a broad, integrated plan for space- and ground-based astronomy and astrophysics for the decade 2023–2032.2 It also lays the foundations for further advances in the following decade. This is the seventh in a sequence of decadal survey studies in this field from the National Academies of Sciences, Engineering, and Medicine. This survey examines the program of record, providing advice on the major projects from prior surveys that are yet to be completed. It also lays out priorities for future investments driven by scientific opportunities. The recommendations in this report advance foundational activities that support the people who drive innovation and discovery, and that promote the technologies and tools needed to carry out the science. The report also recommends sustaining activities on a broad range of cost and time scales, as well as activities that enable future visionary projects by maturing them scientifically and technically. Last, the recommendations set in motion the construction of frontier facilities that will change the view and understanding of the cosmos. The survey is bounded by plausible budget scenarios based on briefings from the sponsoring agencies— the Department of Energy (DOE), the National Aeronautics and Space Administration (NASA), and the National Science Foundation (NSF). Within these bounds, the survey aims high, reflecting this time of great scientific promise and progress, with opportunities to pursue some of the most compelling scientific quests of our times.
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1 National Research Council, 2010, New Worlds, New Horizons in Astronomy and Astrophysics, The National Academies Press, Washington, DC.
2 The statement of task specified a date range of 2022–2032. This has been adjusted to more accurately reflect the range that the survey will affect.
THE SCIENTIFIC OPPORTUNITIES
The survey’s scientific vision is framed around three broad themes that embrace some of the most exciting new discoveries and progress since the start of the millennium and that promise to address some of the most fundamental and profound questions in our exploration of the cosmos. The first theme, Worlds and Suns in Context, builds on revolutionary advances in our observations of exoplanets and stars and aims to understand their formation, evolution, and interconnected nature and to characterize other solar systems, including potentially habitable analogs to our own. New Messengers and New Physics will exploit the new observational tools of gravitational waves and particles, along with temporal monitoring of the sky across the electromagnetic spectrum and wide-area surveys from the ultraviolet and visible to microwave and radio to probe some of the most energetic processes in the universe and also address the nature of dark matter, dark energy, and cosmological inflation. Research in the third theme, Cosmic Ecosystems, will link observations and modeling of stars, galaxies, and the gas and energetic processes that couple their formation, evolution, and destinies.
Within these broad and rich scientific themes, three priority areas motivate recommended investments over the coming decade. “Pathways to Habitable Worlds” is a step-by-step program to identify and characterize Earth-like extrasolar planets, with the ultimate goal of obtaining imaging and spectroscopy of potentially habitable worlds. “New Windows on the Dynamic Universe” is aimed at combining time-resolved multi-wavelength electromagnetic observations from space and the ground with non-electromagnetic signals to probe the nature of black holes, neutron stars, and the explosive events and mergers that give rise to them, and to use signatures imprinted by gravitational waves to understand what happened in the earliest moments in the birth of the universe. “Unveiling the Hidden Drivers of Galaxy Growth” is aimed at revolutionizing our understanding of the origins and evolution of galaxies, from the nature of the tenuous cosmic webs of gas that feed them, to the nature of how this gas condenses and drives the formation of stars.
THE RECOMMENDED PROGRAM
Major leaps in observational capabilities will be realized in the coming decade when new large telescopes and missions commence science operations (see Chapter 7, Table 7.1). Recommended by previous surveys, with some undertaken with international partners, these projects and programs are an essential base upon which the survey’s scientific vision is built. It is essential that these initiatives be completed and that the scientific programs be supported at levels that ensure full exploitation of their potential by the U.S. scientific community.
Going forward, this survey lays out a strategy for federal investments aimed at paving pathways from the foundations of the profession to the bold scientific frontiers.
Large Programs That Forge the Frontiers
These scientific visions—Pathways to Habitable Worlds, New Windows on the Dynamic Universe, and Unveiling the Hidden Drivers of Galaxy Growth—require the major recommended investments in large projects to begin design and construction in the coming 10 years (see Tables S.5 and S.6; Figure S.1).3 In space, achieving the community’s most ambitious and visionary ideas in a sustainable way, and realizing the broad capabilities demanded by the richness of the science, requires a reimagining of the ways in which large missions are planned, developed, and implemented. The Great Observatories Mission and Technology Maturation Program (Table S.5) would provide significant early investments in the
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3 For space, large projects are defined as those with costs exceeding $1.5 billion. For ground-based initiatives, large projects are defined as those exceeding $130 million for the total program investment.
co-maturation of mission concepts and technologies, with appropriate decadal survey input on scope, and with checks and course corrections along the way. Inspired by the vision of searching for signatures of life on planets outside the solar system, and by the transformative capability such a telescope would have for a wide range of astrophysics, the survey recommends that the first mission to enter this program is a large (~6 m aperture) infrared/optical/ultraviolet (IR/O/UV) space telescope. The scientific goals of this mission, when achieved, have the potential to profoundly change the way that human beings view our place in the universe. With sufficient ambition, we are poised scientifically and technically to make this transformational step. This endeavor represents a quest that is on the technical forefront, is of an ambitious scale that only NASA can undertake, and is one where the United States is uniquely situated to lead the world. If maturation proceeds as expected, the survey recommends that formulation and implementation begin by the end of the 2020 decade. To prepare for future large, strategic missions, 5 years after beginning the maturation program for the IR/O/UV mission, the survey recommends commencing mission and technology maturation of both a far-IR and an X-ray large strategic mission, both scoped to have implementation costs in the $3 billion to $5 billion range.
Because of the powerful potential that large (20–40 m) telescopes with diffraction-limited adaptive optics have for astronomy, and because of the readiness of the projects, the survey’s priority for a frontier ground-based observatory is a significant U.S. investment in the Giant Magellan Telescope (GMT) and Thirty Meter Telescope (TMT) projects, ideally as components of a coordinated U.S. Extremely Large Telescope (US-ELT) program. These observatories will create enormous opportunities for scientific progress over the coming decades and well beyond, and they will address nearly every important science question across all three priority science areas. After this, given technical and scientific progress over the past decades, ground-based cosmic microwave background (CMB) studies are poised in the next decade to make a major step forward, and the CMB Stage 4 (CMB-S4) observatory (with support from NSF and DOE) will have broad impact on cosmology and astrophysics. It is also essential to astronomy that the Karl Jansky Very Large Array (VLA) and Very Long Baseline Array (VLBA), which have been the world-leading radio observatories, be replaced by an observatory that can achieve roughly an order of magnitude improvement in sensitivity compared to those facilities. The Next Generation Very Large Array (ngVLA) will achieve this, with a phased approach where design, prototyping, and cost studies are completed and reviewed in advance of commencing construction. Last, neutrino observations are important to understanding some of the most energetic processes in the universe, and the IceCube Generation 2 (IceCube-Gen2) observatory will make advances in important astrophysics questions, although it is beyond the charge of this survey to recommend it.4
Programs That Sustain and Balance the Science
Turning to medium-scale missions and projects, the scientific richness of a broader set of themes—exploring New Messengers and New Physics, understanding Cosmic Ecosystems, and placing Worlds and Suns in Context—as well as the need to capitalize on major existing investments and those coming online in the next decades drive the essential sustaining projects (Tables S.5 and S.6). In space, the highest-priority sustaining activity is a space-based time-domain and multi-messenger program of small- and medium-scale missions. In addition, the survey recommends a new line of probe missions to be competed in broad areas identified as important to accomplish the survey’s scientific goals. For the coming decade, a far-IR mission, or an X-ray mission designed to complement the European Space Agency (ESA) Athena mission, would provide powerful capabilities not possible at the Explorer scale. With science objectives that are more focused compared to a large strategic mission, and a cost cap of $1.5 billion, a cadence of one probe
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4 IceCube is supported and managed by the NSF Division of Physics, rather than the Division of Astronomical Sciences.
mission per decade is realistic. The selection of a probe mission in either area would not replace the need for a future large, strategic mission. For ground-based projects, the highest-priority sustaining activity is a significant augmentation and expansion of mid-scale programs, including the addition of strategic calls to support key survey priorities. The survey also strongly endorses investments in technology development for advanced gravitational wave interferometers, both to upgrade NSF’s Laser Interferometer Gravitational-Wave Observatory (LIGO), and to prepare for the next large facility.5
Foundational Activities
A successful decadal survey strategy requires serious attention to the smaller but vital investments in the foundations of the research. The people who make up the profession are the most fundamental com-
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5 Technology development for gravitational wave detection is funded out of the NSF Division of Physics. The survey strongly endorses the importance of the science to astronomy and astrophysics.
ponent of the research enterprise, without whom the ambitious facilities, instruments, and experiments, as well as the promised transformative discoveries, would lie unfulfilled. Recognizing that diversity is a driver of innovation and that the astronomy and astrophysics enterprise can be at its most innovative only when it maximizes and fully utilizes the broadest range of human talent, the survey forwards several crucial programs (Table S.1) to support early-career entrants, with a strong emphasis on broadening access, removing barriers to participation, and creating an environment that eschews harassment and discrimination of all kinds. The future of the field also requires that greater attention be paid to issues of sustainability and accountability, and several recommendations address these issues. Among the recommendations regarding the state of the profession, the most urgent need is maintenance of accurate data on funding outcomes, because it is sufficiently critical to the other recommendations (Table S.1).
Science cannot progress without the essential support to individual investigators who take the data and transform them into scientific understanding and discovery. Accordingly, augmenting the NSF Astronomy and Astrophysics Grants program is the highest priority among the foundational recommendations. Science also cannot progress without the necessary tools, such as archives, data pipelines, laboratory work, and theoretical tools that provide the essential, cross-cutting foundations. The computational revolution continues to transform the conduct and culture of astronomy through the growing roles of large surveys and shared public data sets, big-team research, applications of machine learning, and numerical simulations, among others, and research investments will need to evolve to adapt to this changing landscape. Several critical areas require a healthier balance in order to optimize the scientific returns on past and future major investments (Table S.2).
The currently operating facilities on the ground and in space, along with the scientists who use them, are the primary engines of scientific discovery and progress in astronomy and astrophysics. In this regard, it is essential to adequately support the costs of operating facilities in space and on the ground, review them regularly during their productive lives, and for ground-based observatories, maintain them as premier facilities with modern, state-of-the-art instrumentation. Table S.3 summarizes this report’s recommendations relative to the agencies’ operational portfolios.
A balanced portfolio that includes a healthy investment in small- and medium-scale projects that are competed, draws from the ingenuity and breadth of the community, and enables science on a broad range of costs and time scales is essential for sustaining a vibrant astronomy and astrophysics program. These activities sustain scientific progress, amplify and enhance return from operating missions and observatories, and respond nimbly to new discovery. The survey recognizes the foundational need for supporting basic technology development and the crucial role that small- and medium-scale projects play in broadening science and as a means of developing the next generation of technologists and instrumentalists. Table S.4 summarizes recommendations aimed at strengthening relevant technological foundations
Enabling Future Visions
The community’s most ambitious and visionary ideas now require timelines that are pan-decadal and even multi-generational. This is particularly true for NASA’s large strategic missions and NSF’s premier observatories that are driven by transformative scientific visions but are technically challenging. They also represent large investments of resources. Optimizing the cadence of major facilities and developing them in a sustainable way that ensures the appropriate level of maturity prior to a decadal or agency commitment and tighter control on ultimate project costs requires new, enabling programs and approaches. The Great Observatories Mission and Technology Maturation Program would provide a new approach for developing large space strategic missions. In addition, for all large projects, the survey provides decision rules and recommends reviews, where required, to ensure technical, scientific, and cost-readiness prior to commitment of major resources. The survey also identifies a few future projects that are targets for significant investment in maturation for consideration by future decadal surveys, as summarized in Tables S.5 and S.6, column 2.
A very large fraction of the astronomical community contributed to this survey through the almost 900 excellent science, activity, program, and state of the profession white papers and through active engagement in town hall meetings. The program laid out in this report represents a collective vision for the future and will require the engagement of a broad community to advance.
Tables S.1 to S.6 summarize the survey’s recommended program, divided into tables that follow the chapter structure of the report. These tables are intended to provide only a capsule summary of the recommendations. The survey’s report provides detailed guidance on the implementation of major programs and emphasizes the range of scales and capabilities necessary for a healthy, balanced, and visionary program. The ordering of projects in the tables below does not indicate priority ranking. The body of the report provides guidance on which programs or projects are the most urgent and have highest priority within their programmatic category, emphasizing that even within a given cost scale, a balance of programmatic function is required.
TABLE S.1 Foundations of the Profession
Recommendation Topic | Agency | Per Year Budget Increases Relative to FY 2019 Agency Budget Allocations (FY 2020$) | Cross-Reference: Section Number, Chapter 3 |
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Faculty diversity, and early-career faculty awards | NSF NASA DOE |
Augmentation of $2.5 million: $1 million NSF; $1 million NASA; $0.5 million DOE |
3.3.2 |
Workforce development/diversity, bridge programs and Minority Serving Institutions partnerships | NSF NASA |
Augmentation of $4.5 million: $1.5 million NSF; $3 million NASA |
3.3.4 |
Undergraduate and graduate “traineeship” funding | NSF NASA DOE |
Augmentation of $3 million: $1 million NSF; $1 million NASA; $1 million DOE |
3.3.4 |
Independent postdoctorate fellowships | NSF NASA |
Augmentation of $1 million: $0.5 million NSF; $0.5 million NASA |
3.3.4 |
Treat discrimination and harassment as professional misconduct | NSF NASA DOE |
Not applicable (N/A) | 3.3.5 |
Collect, evaluate, and report demographic data and indicators pertaining to equitable outcomes | NSF NASA |
Augmentation of $1 million: Split NSF/NASA |
3.3.6 |
Include diversity in evaluation of funding awards | NSF NASA DOE |
N/A | 3.3.6 |
Establish community astronomy model for observatory sites | Community | N/A | 3.4.1 |
Mitigation of radio frequency and optical interference from sources including satellite constellations | NSF NASA |
TBD after evaluation | 3.4.2 |
Climate change mitigation actions | Community | N/A | 3.4.3 |
TABLE S.2 The Research Foundations
Recommendation Topic | Agency | Per Year Budget Increases Relative to FY 2019 Agency Budget Allocations (FY 2020$) | Cross-Reference: Section Number, Chapter 4 |
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Compile and regularly report data on proposal submissions and success rates | NSF NASA DOE |
N/A | 4.2 |
Augmentation to NSF Astronomy and Astrophysics Grants program | NSF | Augmentation ramps up to an additional $16.5 million/yr by 2028 | 4.2.1 |
Augmentation and restoration of annual proposal calls for Astrophysics Theory program | NASA | Augmentation ramps up to an additional $2.5 million/yr (by 2028 | 4.2.2 |
Support for large key projects on Major Research Equipment and Facilities Construction (MREFC) facilities | NSF | N/A | 4.2.3 |
Improve coordination among U.S. data centers supported by NSF and NASA | NSF NASA |
To be determined (TBD) depending on outcome of study | 4.5.1 |
Data pipeline development, archiving for ground-based telescopes | NSF | TBD depending on plan | 4.5.1 |
Augmentation and improved coordination of laboratory astrophysics funding | NSF NASA |
Augmentation of ~$2 million/yr, TBD after plan is developed | 4.5.5 |
TABLE S.3 Sustaining the Operating Portfolio
Recommendation Topic | Agency | Budget (FY 2020$) | Cross-Reference: Section Number, Chapter 5 |
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New MREFC facilities contingent on development of plan for supporting operations and maintenance costs | NSF | N/A | 5.1.1 |
NSF to establish regular cadence of portfolio reviews of operating facilities | NSF | N/A | 5.1.2 |
End Stratospheric Observatory for Infrared Astronomy (SOFIA) operations by 2023, consistent with current NASA plan | NASA | No impact if adopted | 5.2.1 |
TABLE S.4 The Technological Foundations
Recommendation Topic | Agency | Per Year Budget Increase Relative to FY 2019 Agency Budget Allocations (FY 2020$) | Cross-Reference: Section Number, Chapter 6 |
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Augmentation to NASA Astrophysics Research and Analysis program | NASA | Augmentation of $4 million/yr | 6.1.1.1 |
Continue NASA Strategic Astrophysics Technology (SAT) program; expand eligibility to probe mission development | NASA | N/A | 6.1.1.2 |
Augmentation to NSF Advanced Technologies and Instrumentation (ATI) program | NSF | Augmentation of $8 million/yr starting 2023; ramp up to $14 million additional by 2028 (assumes current budget is $6 million/yr) | 6.1.2 |
Review NASA’s balloon program for optimal balance | NASA | TBD depending on outcome of review | 6.2.1.1.1 |
TABLE S.5 New Medium and Large Initiatives: Space
Recommendation Topic | Programmatic Function | Cost Appraisal (FY 2020$) | Cross-Reference: Section Number, Chapter 7 |
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Great Observatories Mission and Technology Maturation Program for Infrared/Optical/Ultraviolet (IR/O/UV) (first half of decade), far-IR and X-ray (second half of decade) missions | Enabling future frontier projects | $1.2 billion this decade | 7.5.1 |
Near-IR/O/UV telescope with high-contrast imaging capability | Frontier project, to begin after maturation program | $11 billion (estimated) | 7.5.2 |
Time Domain and Multi-Messenger Follow-Up program | Sustaining scientific balance and scale | TBD ($500 million–$800 million this decade estimated) | 7.5.3.1 |
Astrophysics Probe Mission program | Sustaining scientific balance and scale | $1.5 billion cost cap | 7.5.3.2 |
TABLE S.6 New Medium and Large Initiatives: Ground
Recommendation Topic | Programmatic Function | Capital Cost (FY 2020$) (TRACE, Appendix A) | Operations Cost (FY 2020$) | Cross-Reference Section Number, Chapter 7 |
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Extremely Large Telescope (ELT) program | Frontier project | $1.7 billion (NSF share of $5.1 billion total project cost) | $32 million/yr (NSF share of $98 million total) | 7.6.1.1, 7.6.1.2 |
Cosmic Microwave Background Stage 4 Observatory (CMB-S4; joint NSF/DOE) | Frontier project | $660 million DOE+NSF; NSF share $273 million | $17 million/yr (NSF share of $40 million/yr) | 7.6.1.3 |
Next Generation Very Large Array (ngVLA) | Enabling development program, followed by construction if possible | $2.5 billion (NSF share of $3.2 billion project cost) | $98 million/yr; NSF share $73 million/yr | 7.6.1.4 |
Augmentation of Mid-Scale Program: open and strategic calls | Sustaining | Ramps up to $50 million/yr total for Mid-Scale Innovations Program and Mid-Scale Research Infrastructure | Operations in total program funding | 7.6.2 |
Technology development for Laser Interferometer Gravitational-Wave Observatory (LIGO) upgrades and for future observatories | Enabling development program for future frontier gravitational wave (GW) observatories | N/A | N/A (not NSF Division of Astronomical Sciences [AST]) | 7.6.3.1 |
IceCube Generation 2 (IceCube-Gen2) | Frontier project | N/A | N/A (not NSF AST) | 7.6.3.2 |