Pathways to Discovery in
Astronomy and
Astrophysics for the
2020s

Committee for a Decadal Survey on Astronomy and Astrophysics 2020 (Astro2020)

Space Studies Board

Board on Physics and Astronomy

Division on Engineering and Physical Sciences

A Consensus Study Report of

THE NATIONAL ACADEMIES PRESS
Washington, DC
www.nap.edu

This study is based on work supported by Grant FA9550-19-1-0330 with the Air Force Office of Scientific Research, Grant DE-SC0019513 with the Department of Energy, Contract NNH17CB02B with the National Aeronautics and Space Administration, and Grant AST-1852611 with the National Science Foundation. Any opinions, findings, conclusions, or recommendations expressed in this publication do not necessarily reflect the views of any agency or organization that provided support for the project.

International Standard Book Number-13: 978-0-309-46734-6
International Standard Book Number-10: 0-309-46734-9
Digital Object Identifier: https://doi.org/10.17226/26141
Library of Congress Control Number: 2023938874

Cover design: Tim Warchocki.

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Suggested citation: National Academies of Sciences, Engineering, and Medicine. 2023. Pathways to Discovery in Astronomy and Astrophysics for the 2020s. Washington, DC: The National Academies Press. https://doi.org/10.17226/26141.

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COMMITTEE FOR A DECADAL SURVEY ON ASTRONOMY AND ASTROPHYSICS 2020 (ASTRO2020): STEERING COMMITTEE

FIONA A. HARRISON, NAS,¹ California Institute of Technology, Co-Chair

ROBERT C. KENNICUTT, JR., NAS, University of Arizona and Texas A&M University, Co-Chair

JULIANNE DALCANTON, University of Washington

TIM DE ZEEUW, Leiden University

ANDREW S. DRIESMAN, Johns Hopkins University Applied Physics Laboratory

JONATHAN J. FORTNEY, University of California, Santa Cruz

GABRIELA GONZÁLEZ, NAS, Louisiana State University

JORDAN A. GOODMAN, University of Maryland

MARC P. KAMIONKOWSKI, NAS, Johns Hopkins University

BRUCE A. MACINTOSH, Stanford University

JACOBUS M. OSCHMANN, Independent Consultant

RACHEL A. OSTEN, Space Telescope Science Institute, Executive Officer

LYMAN A. PAGE, JR., NAS, Princeton University

ELIOT QUATAERT, NAS, Princeton University

WANDA A. SIGUR, NAE,² Independent Consultant

RACHEL SOMERVILLE, Flatiron Institute

KEIVAN G. STASSUN, Vanderbilt University

JEAN L. TURNER, University of California, Los Angeles

PIETER VAN DOKKUM, Yale University

ELLEN G. ZWEIBEL, NAS, University of Wisconsin–Madison

___________________

¹ Member, National Academy of Sciences.

² Member, National Academy of Engineering.

SCIENCE PANELS

PANEL ON COMPACT OBJECTS AND ENERGETIC PHENOMENA

DEEPTO CHAKRABARTY, Massachusetts Institute of Technology, Chair

LAURA B. CHOMIUK, Michigan State University

DANIEL E. HOLZ, University of Chicago

RAFFAELLA MARGUTTI, Northwestern University

JULIE McENERY, NASA Goddard Space Flight Center

PETER I. MÉSZÁROS, The Pennsylvania State University

RAMESH NARAYAN, NAS, Center for Astrophysics | Harvard and Smithsonian

ELIOT QUATAERT, NAS, Princeton University, Steering Committee Liaison

SCOTT M. RANSOM, National Radio Astronomy Observatory

TODD A. THOMPSON, The Ohio State University

PANEL ON COSMOLOGY

DANIEL EISENSTEIN, NAS, Harvard University and Sloan Digital Sky Survey III, Chair

LINDSEY E. BLEEM, Argonne National Laboratory

MARC P. KAMIONKOWSKI, NAS, Johns Hopkins University, Steering Committee Liaison

RACHEL MANDELBAUM, Carnegie Mellon University

MIGUEL F. MORALES, University of Washington

DANIEL M. SCOLNIC, Duke University

MATIAS ZALDARRIAGA, NAS, Institute for Advanced Study

KATHRYN M. ZUREK, California Institute of Technology

PANEL ON GALAXIES

DANIELA CALZETTI, NAS, University of Massachusetts Amherst, Chair

MICHAEL BOYLAN-KOLCHIN, The University of Texas at Austin

HSIAO-WEN CHEN, University of Chicago

ANN E. HORNSCHEMEIER, NASA Goddard Space Flight Center

SUSAN A. KASSIN, Space Telescope Science Institute

AMANDA A. KEPLEY, National Radio Astronomy Observatory

CHARLES C. STEIDEL, NAS, California Institute of Technology

DANIEL K. STERN, NASA Jet Propulsion Laboratory

TOMMASO TREU, University of California, Los Angeles

PIETER VAN DOKKUM, Yale University, Steering Committee Liaison

DAVID H. WEINBERG, The Ohio State University

PANEL ON EXOPLANETS, ASTROBIOLOGY, AND THE SOLAR SYSTEM

VICTORIA S. MEADOWS, University of Washington, Chair

DAVID A. BRAIN, University of Colorado Boulder

IAN J.M. CROSSFIELD, Massachusetts Institute of Technology

COURTNEY D. DRESSING, University of California, Berkeley

JONATHAN J. FORTNEY, University of California, Santa Cruz, Steering Committee Liaison

TIFFANY KATARIA, Jet Propulsion Laboratory

KATHLEEN E. MANDT, Johns Hopkins University Applied Physics Laboratory

MARK S. MARLEY, NASA Ames Research Center

BRITNEY E. SCHMIDT, Cornell University

CHRISTOPHER C. STARK, Space Telescope Science Institute

PANEL ON THE INTERSTELLAR MEDIUM AND STAR AND PLANET FORMATION

LEE W. HARTMANN, University of Michigan, Chair

SEAN M. ANDREWS, Smithsonian Astrophysical Observatory

PHILIP J. ARMITAGE, Stony Brook University

BRUCE T. DRAINE, NAS, Princeton University

KAITLIN M. KRATTER, University of Arizona

KARIN M. SANDSTROM, University of California, San Diego

SNEZANA STANIMIROVIC, University of Wisconsin–Madison

ELLEN G. ZWEIBEL, NAS, University of Wisconsin–Madison, Steering Committee Liaison

PANEL ON STARS, THE SUN, AND STELLAR POPULATIONS

SARBANI BASU, Yale University, Chair

NANCY S. BRICKHOUSE, Center for Astrophysics | Harvard and Smithsonian

ADAM BURGASSER, University of California, San Diego

JULIANNE DALCANTON, University of Washington, Steering Committee Liaison

JENNIFER A. JOHNSON, The Ohio State University

R.T. JAMES McATEER, New Mexico State University

ELISA V. QUINTANA, NASA Goddard Space Flight Center

LOUIS-GREGORY STROLGER, Space Telescope Science Institute

PROGRAM PANELS

PANEL ON AN ENABLING FOUNDATION FOR RESEARCH

DAVID N. SPERGEL, NAS, Princeton University, Chair

MICHAEL BLANTON, New York University

KELLE L. CRUZ, Hunter College

MARK J. DEVLIN, University of Pennsylvania

MEGAN E. DONAHUE, Michigan State University

KEITH A. HAWKINS, The University of Texas at Austin

ALINA A. KIESSLING, Jet Propulsion Laboratory

KARIN ÖBERG, Harvard University

ANGELA V. OLINTO, NAS, University of Chicago

BERNARD J. RAUSCHER, NASA Goddard Space Flight Center

RACHEL SOMERVILLE, Center for Computational Astrophysics, Flatiron Institute, Steering Committee Liaison

JAMES M. STONE, Institute for Advanced Study

PANEL ON ELECTROMAGNETIC OBSERVATIONS FROM SPACE 1

MARCIA J. RIEKE, NAS, University of Arizona, Chair

RUSLAN BELIKOV, NASA Ames Research

REBECCA A. BERNSTEIN, Carnegie Institution for Science

LESTER M. COHEN, Center for Astrophysics | Harvard and Smithsonian

NIKOLE K. LEWIS, Cornell University

BRUCE A. MACINTOSH, Stanford University, Steering Committee Liaison

AMY MAINZER, University of Arizona

MARK P. SAUNDERS, Independent Consultant

EVGENYA L. SHKOLNIK, Arizona State University

GEORGE SONNEBORN, NASA Goddard Space Flight Center

C. MEGAN URRY, NAS, Yale University

PANEL ON ELECTROMAGNETIC OBSERVATIONS FROM SPACE 2

STEVEN M. KAHN, Stanford University, Chair

LISA BARSOTTI, Massachusetts Institute of Technology

ALLISON BARTO, Ball Aerospace and Technologies Corporation

MICHAEL BAY, Bay Engineering Innovations

MARTIN ELVIS, Center for Astrophysics | Harvard and Smithsonian

CHARLES J. HAILEY, Columbia University

CHRYSSA KOUVELIOTOU, NAS, The George Washington University

CHARLES R. LAWRENCE, Jet Propulsion Laboratory

S. HARVEY MOSELEY, JR., Quantum Circuits, Inc.

RESHMI MUKHERJEE, Barnard College

LYMAN A. PAGE, JR., NAS, Princeton University, Steering Committee Liaison

GORDON J. STACEY, Cornell University

PANEL ON OPTICAL AND INFRARED OBSERVATIONS FROM THE GROUND

TIMOTHY M. HECKMAN, NAS, Johns Hopkins University, Chair

DAVID A. BEARDEN, Jet Propulsion Laboratory

DAVID CHARBONNEAU, NAS, Harvard University

SUVI GEZARI, University of Maryland

ANDREA M. GHEZ, NAS, University of California, Los Angeles

JENNY E. GREENE, Princeton University

J. TODD HOEKSEMA, Stanford University

JACOBUS M. OSCHMANN, Independent Consultant, Steering Committee Liaison

RICHARD W. POGGE, The Ohio State University

MASSIMO ROBBERTO, Space Telescope Science Institute

NATASCHA M. FÖRSTER SCHREIBER, Max Planck Institute for Extraterrestrial Physics

DAVID R. SILVA, The University of Texas at San Antonio

PANEL ON PARTICLE ASTROPHYSICS AND GRAVITATION

JOHN F. BEACOM, The Ohio State University, Co-Chair

LAURA CADONATI, Georgia Institute of Technology, Co-Chair

DAVID Z. BESSON, University of Kansas

GABRIELA A. GONZÁLEZ, NAS, Louisiana State University, Steering Committee Liaison

JORDAN A. GOODMAN, University of Maryland, Steering Committee Liaison

ELIZABETH A. HAYS, NASA Goddard Space Flight Center

N. JEREMY KASDIN, University of San Francisco

DAVID B. KIEDA, The University of Utah

ANDREA N. LOMMEN, Haverford College

BRIAN D. METZGER, Columbia University

JAMES H. YECK, University of Wisconsin–Madison

NICOLAS YUNES, University of Illinois at Urbana-Champaign

PANEL ON RADIO, MILLIMETER, AND SUBMILLIMETER OBSERVATIONS FROM THE GROUND

ANDREW J. BAKER, Rutgers, The State University of New Jersey, Chair

JACQUELINE N. HEWITT,¹ Massachusetts Institute of Technology, Vice Chair

HÉCTOR G. ARCE, Yale University

RAVINDER S. BHATIA, Thirty Meter Telescope

TRACY E. CLARKE, Naval Research Laboratory

MATT A. DOBBS, McGill University

DAVID L. KAPLAN, University of Wisconsin–Milwaukee

DANIEL P. MARRONE, University of Arizona

LYNN D. MATTHEWS, Massachusetts Institute of Technology Haystack Observatory

JOAN R. NAJITA, NSF National Optical-Infrared Astronomy Research Laboratory (NOIRLab)

RICHARD L. PLAMBECK, University of California, Berkeley

JEAN L. TURNER, University of California, Los Angeles, Steering Committee Liaison

PANEL ON STATE OF THE PROFESSION AND SOCIETAL IMPACTS

MARGARET M. HANSON, University of Cincinnati, Co-Chair

ENRICO RAMIREZ-RUIZ, University of California, Santa Cruz, Co-Chair

GURTINA BESLA, University of Arizona

PATRICIA T. BOYD, NASA Goddard Space Flight Center

KATHRYNE J. DANIEL, Bryn Mawr College

MARTHA P. HAYNES, NAS, Cornell University

JEDIDAH C. ISLER, Dartmouth University

RACHEL L. IVIE, American Institute of Physics

KATHRYN V. JOHNSTON, Columbia University

CASEY W. MILLER, Rochester Institute of Technology

JESÚS PANDO, DePaul University

JULIE R. POSSELT, University of Southern California

JANE R. RIGBY, NASA Goddard Space Flight Center

WILLIE S. ROCKWARD, Morgan State University

KEIVAN G. STASSUN, Vanderbilt University, Steering Committee Liaison

___________________

¹ Resigned from the panel on April 16, 2020, and did not participate in the panel’s deliberations or the writing of its report.

DECADAL SURVEY ON ASTRONOMY AND ASTROPHYSICS 2020 (ASTRO2020) STAFF

COLLEEN N. HARTMAN, Director, Space Studies Board and Board on Physics and Astronomy²*

JAMES LANCASTER,³ Director, Board on Physics and Astronomy

GREGORY MACK, Senior Program Officer, Board on Physics and Astronomy, Steering Committee Co-Study Director and Panel on Compact Objects and Energetic Phenomena

ABIGAIL A. SHEFFER, Senior Program Officer, Space Studies Board, Steering Committee Co-Study Director and Panel on Electromagnetic Observations from Space 2

DIONNA WISE, Program Coordinator, Space Studies Board, Steering Committee and Panel on State of the Profession and Societal Impacts

MIA BROWN, Research Associate, Space Studies Board, Steering Committee

ALAN ANGLEMAN, Senior Program Officer, Aeronautics and Space Engineering Board, Panel on Particle Astrophysics and Gravitation

SHENAE BRADLEY, Administrative Assistant, Computer Science and Telecommunications Board, Panel on Galaxies

MEGAN CHAMBERLAIN, Senior Program Assistant, Space Studies Board, Panel on Electromagnetic Observations from Space 2, Panel on Optical and Infrared Observations from the Ground, and Panel on Particle Astrophysics and Gravitation

ARTHUR CHARO, Senior Program Officer, Space Studies Board, Panel on Radio, Millimeter, and Submillimeter Observations from the Ground

DWAYNE DAY, Senior Program Officer, Aeronautics and Space Engineering Board, Panel on Electromagnetic Observations from Space 1

GREG EYRING, Senior Program Officer, National Materials and Manufacturing Board, Panel on the Interstellar Medium and Star and Planet Formation, Panel on an Enabling Foundation for Research, and Panel on State of the Profession and Societal Impacts

SANDRA GRAHAM, Senior Program Officer, Space Studies Board, Panel on Stars, the Sun, and Stellar Populations

GAYBRIELLE HOLBERT, Program Assistant, Space Studies Board, Panel on Stars, the Sun, and Stellar Populations

AMISHA JINANDRA, Associate Program Officer, Board on Physics and Astronomy, Panel on Exoplanets, Astrobiology, and the Solar System

CHRISTOPHER JONES, Program Officer, Board on Physics and Astronomy, Panel on Exoplanets, Astrobiology, and the Solar System

JAMES MYSKA, Program Officer, National Materials and Manufacturing Board, Panel on Cosmology

DANIEL NAGASAWA, Program Officer, Space Studies Board, Panel on State of the Profession and Societal Impacts

ERIK SAARI, Administrative Assistant, Board on Army Research Development,⁴Panel on Compact Objects and Energetic Phenomena, and Panel on Exoplanets, Astrobiology, and the Solar System

ERIK SVEDBERG, Senior Program Officer, National Materials and Manufacturing Board, Panel on Galaxies, and Panel on Optical and Infrared Observations from the Ground

___________________

² Since April 2021.

^* We want to thank the following: Senior Scholar and former Board on Physics and Astronomy Board Director Donald C. Shapero; Christine Mirzayan Science and Technology Policy Fellows Sara Crandall and Emily Moravec; and Lloyd V. Berkner Space Policy Interns Jacob Abrahams, Robert Bullard, Benjamin Cassese, Lily Davey, Katherine Dzurilla, Phoebe Kinzelman, Tarini Konchady, Sarah Moran, Osase Omoruyi, Genevieve Payne, and Cindy Vo.

³ Retired May 2021.

⁴ Until November 30, 2019.

LINDA WALKER, Program Coordinator, Board on Physics and Astronomy, Panel on Cosmology, Panel on the Interstellar Medium and Star and Planet Formation, Panel on an Enabling Foundation for Research, Panel on Electromagnetic Observations from Space 1, and Panel on Radio, Millimeter, and Submillimeter Observations from the Ground

BOARD ON PHYSICS AND ASTRONOMY

ANDREW J. LANKFORD, University of California, Irvine, Chair

MEIGAN ARONSON, University of British Columbia

WILLIAM BIALEK, NAS, Princeton University

JILL DAHLBURG, Naval Research Laboratory (retired)

SALLY DAWSON, Brookhaven National Laboratory

LOUIS F. DIMAURO, The Ohio State University

WENDELL T. HILL III, University of Maryland

ALAN J. HURD, Los Alamos National Laboratory

CHUNG-PEI MA, University of California, Berkeley

ANGELA VILLELA OLINTO, University of Chicago

DAVID H. REITZE, California Institute of Technology

SUNIL SINHA, University of California, San Diego

RISA H. WECHSLER, Stanford University

WILLIAM A. ZAJC, Columbia University

STAFF

JAMES C. LANCASTER,⁵ Director

COLLEEN N. HARTMAN,⁶ Director

NEERAJ P. GORKHALY, Associate Program Officer

AMISHA JINANDRA, Associate Program Officer

CHRISTOPHER J. JONES, Program Officer

RADAKA LIGHTFOOT, Finance Business Partner

GREGORY MACK, Senior Program Officer

LINDA WALKER, Program Coordinator

SPACE STUDIES BOARD

MARGARET G. KIVELSON, NAS, University of California, Los Angeles, Chair

GREGORY P. ASNER, NAS, Carnegie Institution for Science

ADAM S. BURROWS, NAS, Princeton University

JAMES H. CROCKER, NAE, Lockheed Martin Space Systems Company

MARY LYNNE DITTMAR, Coalition for Deep Space Exploration

JEFF DOZIER, University of California, Santa Barbara

MELINDA DARBY DYAR, Mount Holyoke College

ANTONIO L. ELIAS, NAE, Orbital ATK, Inc.

___________________

⁵ Retired May 2021.

⁶ Since April 2021.

VICTORIA E. HAMILTON, Southwest Research Institute

CHRYSSA KOUVELIOTOU, NAS, The George Washington University

DENNIS P. LETTENMAIER, NAE, University of California, Los Angeles

ROSALY M. LOPES, Jet Propulsion Laboratory

STEPHEN J. MACKWELL, American Institute of Physics

DAVID J. McCOMAS, Princeton University

LARRY J. PAXTON, Johns Hopkins University

ELIOT QUATAERT, NAS, Princeton University

MARK SAUNDERS, Independent Consultant

BARBARA SHERWOOD LOLLAR, University of Toronto

HOWARD SINGER, National Oceanic and Atmospheric Administration

HARLAN E. SPENCE, University of New Hampshire

ERIKA B WAGNER, Blue Origin, LLC

PAUL D. WOOSTER, Space Exploration Technologies

EDWARD L. WRIGHT, NAS, University of California, Los Angeles

STAFF

COLLEEN N. HARTMAN, Director

ALAN ANGLEMAN, Associate Director

ALEXIS BHADHA, Financial Assistant

MIA BROWN, Research Associate

MEGAN CHAMBERLAIN, Senior Program Assistant

ARTHUR CHARO, Senior Program Officer

SANDRA GRAHAM, Senior Program Officer

GAYBRIELLE HOLBERT, Senior Program Assistant

MEG KNEMEYER, Senior Finance Business Partner

DANIEL NAGASAWA, Program Officer

CELESTE A. NAYLOR, Information Management Associate

TANJA PILZAK, Manager, Program Operations

ANDREA REBHOLZ, Program Coordinator

ABIGAIL SHEFFER, Senior Program Officer

DAVID SMITH, Senior Program Officer

DIONNA WISE, Program Coordinator

Preface

The summary charge for the Committee for a Decadal Survey of Astronomy and Astrophysics (Astro2020; hereafter the “steering committee”) reads as follows:

The complete statement of task and its scope is provided in Appendix A of this report. The steering committee, with inputs from 13 expert panels encompassing the breadth of astronomy and astrophysics, was specifically asked to (1) provide an overview of the current state of astronomy and astrophysics science, and technology research in support of that science, with connections to other scientific areas where appropriate; (2) identify the most compelling science challenges and frontiers in astronomy and astrophysics, which shall motivate the committee’s strategy for the future; (3) develop a comprehensive research strategy to advance the frontiers of astronomy and astrophysics for the period 2022–2032 that will include identifying, recommending, and ranking the highest-priority research activities; (4) utilize and recommend decision rules, where appropriate, that can accommodate significant but reasonable deviations in the projected budget or changes in urgency precipitated by new discoveries or unanticipated competitive activities; (5) assess the state of the profession, including workforce and demographic issues in the field, identify areas of concern and importance to the community, and where possible, provide specific, actionable, and practical recommendations to the agencies and community to address these areas.

Astro2020 was sponsored by the National Aeronautics and Space Administration (NASA), the National Science Foundation (NSF), the Department of Energy (DOE) Office of High Energy Physics, and the Air Force Office of Space Research (AFOSR). These federal agencies all participate in different aspects of the U.S. space- and ground-based astronomy and astrophysics program. Internally, the decadal survey effort at the National Academies was a joint project of the Board on Physics and Astronomy and the Space Studies

Board. This is the seventh decadal plan for astronomy and astrophysics conducted over the history of the National Academies.

The scope of the science assessed by the decadal survey is broad, encompassing all aspects of observational, theoretical, and computational astronomy, including ground-based solar observations, but specific activity recommendations were limited to those administered by the NSF Division of Astronomical Sciences and the NASA Astrophysics Division. Scientific areas in astronomy and astrophysics pursued by the DOE Office of High Energy Physics were also included in the study, but activity recommendations were limited to NSF and NASA as described above.

The committee was also tasked with assessing three space projects, the Nancy Grace Roman Space Telescope (formerly Wide Field Infrared Survey Telescope), Athena (Advanced Telescope for High-Energy Astrophysics), and LISA (Laser Interferometer Space Antenna)—the latter two being European-led missions with significant NASA participation. These three projects were highly ranked priorities for the 2010 New Worlds New Horizons decadal survey, also called Astro2010, and are under development but not yet launched.¹ The committee was invited to comment on the status and future direction of NASA support for these projects, but they were not considered together with nor ranked against new projects proposed for the coming decade. Likewise, the survey was invited to consider the status and evolution of ongoing programs within NASA’s program of record.

STUDY PROCESS AND PARTICIPANTS

Organization of the Astro2020 decadal survey, including the steering committee and 13 expert panels, began with the appointment of the co-chairs in late 2018. The steering committee consisted of 20 members, including the co-chairs. Members were selected to cover as fully as possible the scientific scope of the survey, the range of observational (ground, space, and particle/gravitational astrophysics) and theoretical disciplines, as well as technical and managerial background in space and/or ground-based facilities, and to comprise as representative a group of experts as possible in terms of individual, institutional, and geographical demographics. National Academies policies governing potential conflicts of interest by steering committee and panel members were strictly enforced. In particular, broad and open-minded thinkers were sought out as opposed to advocates for individual missions or subfields. The role of the Executive Officer was also redefined for this survey to that of a full voting member of the steering committee, with additional administrative and coordination responsibilities as part of the leadership team.

All meetings and deliberations for the survey operated under a code of conduct to guide discussions. This code of conduct was developed in addition to the National Academies policy on sexual harassment and bullying for committee members, panelists, and meeting attendees, and in addition to a code of conduct for National Academy of Sciences members. The statement includes a recognition of strongly held, possibly differing opinions; a dedication to open dialogue and open exchange of ideas; and professional, civil, and collegial treatment of colleagues so that an open exchange of ideas can occur.

During the course of the panel and steering committee meetings, a number of public information-gathering sessions were held. These included briefings by the agencies (NASA, NSF, DOE), invited presentations by selected projects to the program panels, and other informational sessions sponsored by the other panels or the steering committee. Throughout the survey, the representatives of all three agencies urged the committee to be “ambitious”² and “aspirational,”³ and the committee hopes that it has risen to this challenge.

___________________

¹ National Research Council, 2010, New Worlds, New Horizons in Astronomy and Astrophysics, The National Academies Press, Washington, DC.

² Presentation to Astro2020 committee by Paul Hertz, NASA Astrophysics Division, July 2019.

³ Presentation to Astro2020 committee by Ralph Gaume, NSF Division of Astronomical Sciences, July 2019.

The charges of the expert panels were similar to those of the Astro2010 survey, but with a few important changes. The number of science panels was increased from five to six to accommodate the very rapid growth over the previous decade of exoplanetary astronomy and multi-messenger astrophysics, while preserving balance across all subject areas. The basic programmatic panel structure from Astro2010 was also retained, except that the Panel on Electromagnetic Observations from Space was divided into two panels, in order to accommodate the very large number of project proposals and community white papers in that area. Last, two new panels for Astro2020 were appointed—the Panel on an Enabling Foundation for Research (program panel) was charged with evaluating cross-cutting supporting programs (e.g., grants programs, laboratory astrophysics, data archiving and data science, computation, theory), and the Panel on State of the Profession and Societal Impacts (SoPSI) was charged to advise the steering committee on this specific area in its statement of task. These 13 appointed panels (six science, six program, and one state of the profession) comprised 127 members. In addition, a steering committee “liaison” member was appointed to each panel to facilitate the flow of information and communication between panels and the main survey committee. The liaisons participated in the panel discussions but did not hold formal voting rights. In all, 141 individuals participated in the panel deliberations with a purpose of providing input to the steering committee. Each panel drafted its own report, with suggestions for the steering committee to consider, as it held its own deliberations to reach its recommendations for the main report. To underscore the importance of the panel reports, they have been published together with this main report as appendixes.

The science panels were asked to provide a brief review of the current state of the science in their topic areas and determine four important science questions to be addressed in the next decade and one area that shows great promise for discovery. The program panels were charged to assess the ability of current and proposed projects under consideration to address the science panels’ questions and discovery areas, to comment on the Technical, Risk, and Cost Evaluations (TRACEs) of the proposed projects, to identify key areas of technical development or precursor research activities, and to discuss the balance of small, competitively selected activities versus larger strategic investments needed to address the science questions. The program panels were not asked to prioritize or rank projects, but rather to suggest to the steering committee the projects with the best potential to realize the capabilities needed to address the science panels’ questions and discovery areas. The SoPSI panel was asked to gather information on the health and demographics of the astronomy and astrophysics community and make actionable suggestions to the steering committee on the topics of demographics, diversity and inclusion, workplace climate, workforce development, education, public outreach, and relevant areas of astronomy and public policy. Further information about the charges to the panels is found in Appendix A.

The information-gathering and deliberative phases of Astro2020 were carefully coordinated. Members of the astronomical community were invited to submit white papers to the survey, and these papers formed the foundation and starting point for all of the panel deliberations. In the first phase, 572 science white papers were received in early 2019. A second call for “activity, project, or state of profession consideration” (APC) white papers in July 2019 elicited 294 responses. Every white paper was assigned to and read by one or more of the panels.

The panel meetings themselves were phased. The science panels each held two formal meetings, the program panels each held three formal meetings, and all held several additional teleconferences. Meetings of the science panels took place during the second half of 2019, so that the priorities emerging from the reports of those panels could be incorporated into the program panel deliberations. The science panel chairs presented their findings to the steering committee and the program panels at a face-to-face meeting in December 2019 and delivered their written reports in early 2020. The program panels’ meetings began in November 2019, and they presented their results to the steering committee in May 2020 and delivered initial written reports in June 2020. The SoPSI panel met and deliberated on an independent schedule,

including holding a public listening session at the American Astronomical Society meeting on January 6, 2020. The SoPSI report was fully incorporated into the overall deliberations and prioritization phases of the steering committee activities.

During the course of the panel deliberations, a number of other inputs were received, and these were especially important for the program panels. After an initial review of all projects proposed for a given panel area, the panels issued requests for information (RFIs) from selected projects to obtain more detailed information that was initially provided in the respective APCs. These included all of the large space and ground “flagship” proposals and selected examples of smaller projects. Selected projects were also invited to present summaries to their respective program panels in public sessions. Many of these projects then underwent a detailed TRACE study, conducted by an independent contractor (The Aerospace Corporation). This independent analysis was mandated by the 2008 NASA Authorization Act, which “directs the Administrator to enter into agreements periodically with the National Academies for decadal surveys to take stock of the status and opportunities for Earth and space science discipline fields and aeronautics research and to recommend priorities for research and programmatic areas over the next decade.”⁴ Additionally, the act “requires that such agreements include independent estimates of life cycle costs and technical readiness of missions assessed in the surveys whenever possible.” In-house analyses of technology readiness, risk, and cost estimates provided by the project teams themselves supplemented this analysis. Details of the TRACE process are provided in Appendix O of this report. This process was formerly labeled “Cost and Technical Evaluation” (CATE) and was conducted for recent National Academies surveys in planetary science and solar and space physics, as well as Astro2010.

The schedule for this review was impacted by two outside events—a 35-day government shutdown from December 2018 to January 2019, and the COVID-19 pandemic beginning in 2020. The shutdown happened just as science white papers were being solicited, so the deadline for submissions was delayed by a month. The impacts of the COVID-19 pandemic were much more severe. The initial disruptions in March and April 2020 occurred when the program panels were completing their final meetings. Final panel deliberations were held virtually, and delivery of the panel reports to the steering committee were delayed by up to 2 months as everyone adjusted to the new reality of working, caring for children, teaching, and performing service to the community, all while under a stay-at-home order. The greatest impact was on the deliberations of the steering committee, which needed to replace its remaining schedule of four 3- to 4-day face-to-face meetings (out of six total) with more than 20 all-day Zoom meetings. Early into the pandemic, the survey co-chairs and National Academies’ staff decided not to allow the disruptions to compromise the quality or integrity of the survey, and the inevitable result was a several month delay from the original schedule. Included in these virtual meetings were presentations of preliminary results by the program and SoPSI panels during the summer of 2020.

After the panel reports were received and assembled, the steering committee proceeded with the main prioritization discussions, fully informed by the panel reports. The steering committee addressed a few additional topics that were not taken up in full by a program panel (e.g., satellite constellations and radio frequency interference). In such cases, working groups were appointed within the steering committee or by committee and cross-panel working groups. The steering committee’s deliberations were aided by the introduction of innovative strategies to assist in reaching consensus in the virtual environment necessitated by COVID-19, such as online voting tools, collaborative online document editing, the utilization of various videoconferencing features, and asynchronous deliberations (Figure P.1).

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⁴ H.R. 6063—National Aeronautics and Space Administration Authorization Act of 2008, P.L. 110-422, Section 1104, https://www.congress.gov/bill/110th-congress/house-bill/6063.

Acknowledgments

The completion of an undertaking of this scale and importance relies on the contributions of many, and we conclude this introduction by thanking some of the key people. The members of the steering committee, the panel chairs, and the members of the panels contributed tirelessly to the effort, even after the onset of the pandemic extended the timetables and the complexity of their activities. One individual in particular, Executive Officer Rachel Osten, provided extraordinary service as a logistical and scientific coordinator, valued committee member, and advisor to the co-chairs, and is amply deserving of special mention.

The foundation materials for Astro2020 were the 867 science and activity, project, and state of profession consideration white papers, which were contributed by thousands of authors from around the astronomical community. The quality of those papers testified to the effort and thought that went into their preparation, and we express our heartfelt thanks to everyone who participated in this effort and made this a truly community-based survey.

We are also grateful to the members of our sponsoring agencies, especially Ralph Gaume at the National Science Foundation, Paul Hertz at NASA, and Kathleen Turner at the Department of Energy, and their staffs for sharing their time during the early phases of the survey to provide comprehensive background information and guidance, and for responding to our many requests for further background and statistical information.

The Technical, Risk, and Cost Evaluations assessments of the large projects considered by Astro2020 were carried out by the Aerospace Corporation, and we thankfully acknowledge the contributions of their team members, including, in particular, Randy Persinger and Matthew Marshall. We also thank the many experts who generously contributed their help to the steering committee or its panels as consultants. These include Steven Battel (Battel Engineering), who provided early advice on the setup of the survey processes, and Justin Jonas (South African Radio Astronomy Observatory), Joseph McMullin (Square Kilometre Array Organisation), James Moran (Harvard-Smithsonian Center for Astrophysics), and Antony Schinckel (Commonwealth Scientific and Industrial Research Organisation), who provided expert technical advice to the Panel on Radio, Millimeter, and Submillimeter Observations from the Ground. Sherard Robbins (University of Arizona) kindly served as the facilitator of the Panel on State of the Profession and Societal Impacts listening session at the American Astronomical Society meeting.

The scientific vision and recommended strategic program arising from this process are presented in the remainder of this report and will not be summarized here. As with all of the preceding astronomy and astrophysics surveys, difficult choices were necessary, but that is the main reason for conducting these decadal reviews.

We hope that we have provided not only an ambitious, inspirational, and aspirational vision and roadmap for the coming decade but also a pathway toward realizing even greater objectives in the future.

Fiona Harrison and Robert Kennicutt, Co-Chairs
Committee for a Decadal Survey on Astronomy and Astrophysics 2020

Reviewers

This Consensus Study Report was reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise. The purpose of this independent review is to provide candid and critical comments that will assist the National Academies of Sciences, Engineering, and Medicine in making each published report as sound as possible and to ensure that it meets the institutional standards for quality, objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process.

We thank the following individuals for their review of this report:

Main Report

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¹ Member, National Academy of Sciences.

Science Panel Appendixes

Program Panel Appendixes

Panel on Electromagnetic Observations from Space 1

Panel on Electromagnetic Observations from Space 2

Panel on Optical and Infrared Observations from the Ground

Panel on Particle Astrophysics and Gravitation

Panel on Radio, Millimeter, and Submillimeter Observations from the Ground

Panel on State of the Profession and Societal Impacts

Although the reviewers listed above provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations of this report nor did they see the final draft before its release. The review of this report was overseen by Charles F. Kennel, NAS, University of California, San Diego, and Rosalba Perna, State University of New York at Stony Brook. They were responsible for making certain that an independent examination of this report was carried out in accordance with the standards of the National Academies and that all review comments were carefully considered. Responsibility for the final content rests entirely with the authoring committee and the National Academies.

Contents

SUMMARY

1 PATHWAYS TO DISCOVERY: FROM FOUNDATIONS TO FRONTIERS

2 A NEW COSMIC PERSPECTIVE

3 THE PROFESSION AND ITS SOCIETAL IMPACTS: GATEWAYS TO SCIENCE, PATHWAYS TO DIVERSITY, EQUITY, AND SUSTAINABILITY

4 OPTIMIZING THE SCIENCE: FOUNDATIONS

5 EVALUATING AND BALANCING THE OPERATIONAL PORTFOLIO

6 TECHNOLOGY FOUNDATIONS AND SMALL- AND MEDIUM-SCALE SUSTAINING PROGRAMS

7 REALIZING THE OPPORTUNITIES: MEDIUM- AND LARGE-SCALE PROGRAMS

APPENDIXES

A Statement of Task, Additional Guidance, and Panel Descriptions

B Report of the Panel on Compact Objects and Energetic Phenomena

C Report of the Panel on Cosmology

D Report of the Panel on Galaxies

E Report of the Panel on Exoplanets, Astrobiology, and the Solar System

F Report of the Panel on the Interstellar Medium and Star and Planet Formation

G Report of the Panel on Stars, the Sun, and Stellar Populations

H Report of the Panel on an Enabling Foundation for Research

I Report of the Panel on Electromagnetic Observations from Space 1

J Report of the Panel on Electromagnetic Observations from Space 2

K Report of the Panel on Optical and Infrared Observations from the Ground

L Report of the Panel on Particle Astrophysics and Gravitation

M Report of the Panel on Radio, Millimeter, and Submillimeter Observations from the Ground

N Report of the Panel on State of the Profession and Societal Impacts

O Independent Technical, Risk, and Cost Evaluation

P Acronyms and Abbreviations

Q Committee and Panel Biographical Information