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Introduction

The Pathways to Discoveries in Astronomy and Astrophysics for the 2020s¹ (Astro2020) decadal survey recommended that the

Responding to this recommendation, NASA requested that the National Academies of Sciences, Engineering, and Medicine conduct this review through the CAA. The CAA established a Roman Observations Working Group (ROWG) led by CAA member Shaul Hanany to collect evidence and report its findings and conclusions to the CAA. CAA member Elizabeth Hays assisted with leading working sessions during the study. The CAA has approved this consensus report.

The charge to the CAA is given in Appendix B. In responding to this charge, the committee considered observing time allocations subject to the constraints of existing science objectives and mission requirements. The CAA did not consider options that would have eliminated or significantly replaced Roman’s science objectives as directed by New Worlds, New Horizons in Astronomy and Astrophysics² (Astro2010).

The working group was convened on February 24, 2022, and had 22 nearly weekly Zoom meetings through July 21, 2022, to gather information and deliberate. A broad array of experts was invited to provide information and opinions in sessions that were open to the public. The experts addressed questions the committee posed regarding the scientific reach and goals of Roman’s core community as well as GA surveys and the state of the survey designs. The CAA has also heard from the Roman Science Interest Group³ and from Infrared Processing and Analysis Center (IPAC) and Space Telescope Science Institute (STScI) representatives—the two institutions serve as the Roman Science Support and Operations Centers, respectively. The CAA thanks the experts for their time and considered responses. The experts consulted, listed in alphabetical order along with their institutions and relevant credentials or topical areas, were as follows: Lee Armus (IPAC, California Institute of Technology [Caltech]; Roman science lead), Vanessa Bailey (NASA Jet Propulsion Laboratory [JPL]; Roman coronagraph science team), Olivier Dore (NASA JPL; Roman High Latitude Wide Area Survey), Daniel Eisenstein (Harvard University; cosmology), Ryan Foley (University of California, Santa Cruz; supernovae), Scott Gaudi (The Ohio State University; exoplanets), George Helou (IPAC, Caltech; executive director), Paul Hertz (NASA Headquarters; Astrophysics Division director), Ryan Hickox (Dartmouth College; Roman Science Interest Group), Christopher Hirata (The Ohio State University; Roman High Latitude Wide Area Survey), Renee Hlozek (University of Toronto; supernovae), John MacKenty (STScI; senior scientist and Hubble Space

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¹ National Academies of Sciences, Engineering, and Medicine, 2021, Pathways to Discovery in Astronomy and Astrophysics for the 2020s, prepublication release, Washington, DC: The National Academies Press.

² National Research Council, 2010, New Worlds, New Horizons in Astronomy and Astrophysics, Washington, DC: The National Academies Press, https://doi.org/10.17226/12951.

³ NASA, “Roman Science Interest Group: Meetings,” https://roman.gsfc.nasa.gov/science/rsig_meetings.html.

Telescope mission scientist), Julie McEnery (NASA Goddard Space Flight Center [GSFC]; Roman senior project scientist), Roberta Paladini (IPAC, Caltech; GA, galactic stellar populations), James Rhoads (NASA GSFC; GA, galaxy evolution), Jason Rhodes (NASA JPL; cosmology), Brant Robertson (University of California, Santa Cruz; GA, galaxy formation), Ken Sembach (STScI; former director), Rachel Street (Las Cumbres Observatory; exoplanets), Jason Tumlinson (STScI; GA, circumgalactic medium), David Weinberg (The Ohio State University; Roman High Latitude Wide Area Survey, cosmology, and chemical evolution), and Benjamin Williams (University of Washington; GA, stellar populations). The full list of meeting agendas is available at the CAA website.⁴

Throughout its work and in this report the committee consulted several documents, some of which were already in the public domain and some prepared by the Roman project for the purpose of this review. Many of the documents have been posted by NASA in a publicly available repository at https://asd.gsfc.nasa.gov/romancaa. The key documents and their reference acronyms used in the rest of the report are the following:

• “Roman Observations and Design Reference Mission,” February 24, slide presentation (DRM)
• “Roman Space Telescope Science Requirements Document,” RST-SYS-REQ-0020, Revision C (SRD)
• Wide-Field InfraRed Survey Telescope-Astrophysics Focused Telescope Assets WFIRST-AFTA Final Report⁵ (SDT-13)
• Wide-field InfraRed Survey Telescope-Astrophysics Focused Telescope Assets WFIRST-AFTA 2015 Report⁶ (SDT-15)
• New Worlds, New Horizons in Astronomy and Astrophysics (Astro2010)
• Pathways to Discovery in Astronomy and Astrophysics for the 2020s (Astro2020)

Where this report quotes values and parameters relating to the Roman surveys, it uses the values in the DRM. In this report, the phrase “the committee” or “this committee” refers to the CAA.

It is not within the CAA’s statement of task to provide recommendations in this report. The committee is providing findings and conclusions that use non-prescriptive language.

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⁴ National Academies of Sciences, Engineering, and Medicine, “Committee on Astronomy and Astrophysics,” https://www.nationalacademies.org/our-work/committee-on-astronomy-and-astrophysics.

⁵ D. Spergel, N. Gehrels, J. Breckinridge, M. Donahue, A. Dressler, B. S. Gaudi, T. Greene, et al., 2013, Wide-Field InfraRed Survey Telescope-Astrophysics Focused Telescope Assets WFIRST-AFTA Final Report, https://arxiv.org/ftp/arxiv/papers/1305/1305.5422.pdf.

⁶ D. Spergel, N. Gehrels, C. Baltay, D. Bennett, J. Breckinridge, M. Donahue, A. Dressler, et al., 2015, Wide-Field InfraRed Survey Telescope-Astrophysics Focused Telescope Assets WFIRST-AFTA 2015 Report, https://arxiv.org/ftp/arxiv/papers/1503/1503.03757.pdf.