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ExEP Gap List, Rev D JPL D: 1792073 Release Date: January 1, 2021 Page 1 of 29

Approved by:

Dr. Gary Blackwood Date Program Manager, Exploration Program Office NASA/Jet Propulsion Laboratory

Dr. Douglas Hudgins Date Program Scientist Exoplanet Exploration Program Science Mission Directorate NASA Headquarters

EXOPLANET EXPLORATION PROGRAM Science Gap List 2021

Karl Stapelfeldt, Program Chief Scientist

Eric Mamajek, Deputy Program Chief Scientist Exoplanet Exploration Program JPL CL#21-0379 CL#21-0379 JPL Document No: 1792073 ExEP Science Gap List, Rev D JPL D: 1792073 Release Date: January 1, 2021 Page 2 of 29

Cover Art Credit: NASA/JPL-Caltech. Artist conception of the K2-138 exoplanetary system, the first multi- system ever discovered by citizen scientists1. K2-138 is an orangish (K1) about 200 away, with five known all between the size of Earth and orbiting in a very compact architecture. The planet’s orbits form an unbroken chain of 3:2 resonances, with orbital periods ranging from 2.3 and 12.8 days, orbiting the star between 0.03 and 0.10 AU. The limb of the hot sub-Neptunian world K2-138 f looms in the foreground at the bottom, with close neighbor K2-138 e visible (center) and the innermost planet K2-138 b transiting its star. The discovery study of the K2-138 system was led by Jessie Christiansen and collaborators (2018, Astronomical Journal, Volume 155, article 57). This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. This document has been cleared for public release (CL#21-0379).

© 2021 California Institute of Technology. Government sponsorship acknowledged.

1 https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA22088

Exoplanet Exploration Program JPL CL#21-0379 ExEP Science Gap List, Rev D JPL D: 1792073 Release Date: January 1, 2021 Page 3 of 29

Approved by:

Dr. Gary Blackwood Date Program Manager Exoplanet Exploration Program Office NASA/Jet Propulsion Laboratory

Dr. Douglas Hudgins Date Program Scientist Exoplanet Exploration Program Science Mission Directorate NASA Headquarters

Dr. Hannah Jang-Condell Date Deputy Program Scientist Exoplanet Exploration Program Science Mission Directorate NASA Headquarters

Created by:

Dr. Karl Stapelfeldt Chief Program Scientist Exoplanet Exploration Program Office NASA/Jet Propulsion Laboratory California Institute of Technology

Dr. Eric Mamajek Deputy Program Chief Scientist Exoplanet Exploration Program Office NASA/Jet Propulsion Laboratory California Institute of Technology

Exoplanet Exploration Program JPL CL#21-0379 ExEP Science Gap List, Rev D JPL D: 1792073 Release Date: January 1, 2021 Page 4 of 29 The 2021 Exoplanet Exploration Program (ExEP) Science Gap List

Compiled and maintained by: Dr. Karl Stapelfeldt, Program Chief Scientist Dr. Eric Mamajek, Deputy Program Chief Scientist NASA Exoplanet Exploration Program Jet Propulsion Laboratory, California Institute of Technology

The Exoplanet Exploration Program (ExEP) is chartered by the Astrophysics Division (APD) of NASA’s Science Mission Directorate (SMD) to carry out science, research, and technology tasks that advance NASA’s science goal to “Discover and study planets around other , and explore whether they could harbor life.” ExEP’s three aims are:

• discovering planets around other stars, • characterizing their properties, and • identifying candidates that could harbor life

ExEP serves NASA and the community by acting as a focal point for exoplanet science and technology, managing research and technology initiatives, facilitating access to scientific data, and integrating the results of previous and current missions into a cohesive strategy to enable future discoveries. ExEP serves the critical function of developing the concepts and technologies for exoplanet missions, in addition to facilitating science investigations derived from those missions. ExEP manages development of mission concepts, including key technologies, as directed by NASA HQ, from their early conceptual phases into pre-Phase A.

The goal of the ExEP Science Plan2 is to show how the Agency can focus its science efforts on the work needed to realize the goal of finding and characterizing habitable , within the context of community priorities. The ExEP Science Plan consists of three documents, which will be updated periodically, which respond directly to the ExEP Program Plan:

• ExEP Science Development Plan (SDP) • ExEP Science Gap List (SGL) (this document) • ExEP Science Plan Appendix (SPA)

The long-term online home of the science plan documents is: https://exoplanets.nasa.gov/exep/science-overview/.

The ExEP Science Development Plan (SDP) reviews the program’s objectives, the role of scientific investigations in ExEP, important documentation, and the programmatic framework for ExEP science.

2 Much of this preamble text is drawn from the longer introduction to the ExEP Science Plan Appendix (SPA), which provides further context for the ExEP Science Plan.

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This document, the ExEP Science Gap List (SGL), tabulates program “science gaps”, which are defined as either:

• the difference between knowledge needed to define requirements for specified future NASA exoplanet missions and the current state of the art, or

• knowledge which is needed to enhance the science return of current and future NASA exoplanet missions.

Making the gap list public signals to the broader community where focused science investigations are needed over the next 3-5 in support of ExEP goals. The ExEP Science Gap List represents activities and investigations that will advance the goals of NASA’s Exoplanet Exploration Program, and provides brief summaries in a convenient tabular format. All ExEP approaches, activities, and decisions are guided by science priorities, and those priorities are presented and summarized in the ExEP Science Gap List.

The Science Plan Appendix (SPA), lays out the scientific challenges that must be addressed to advance the goals of NASA’s Exoplanet Exploration Program. While the Program Science Development Plan is expected to remain stable over many years, the Science Gap List will be updated annually, and this Science Plan Appendix will be updated as needed approximately every two years. Entries in the Science Gap List will map to sections of the Science Plan Appendix.

The most recent community report relevant to the NASA ExEP is the National Academies’ Exoplanet Science Strategy (ESS) released in September 20183. The ESS report provides a broad- based community assessment of the state of the field of exoplanet science and recommendations for future investments. The National Academies also released the report An Strategy for the Search for Life in the Universe in October 20184. NASA HQ is considering responses to the Exoplanet Science Strategy and Astrobiology Strategy reports. One response was to charter the “Extreme Precision Working Group” (EPRV-WG), which developed and delivered a blueprint for a strategic EPRV initiative to NASA and NSF in March 20205. The Astro2020 Decadal Survey is expected to strongly consider the recommendations of the ESS report, and their direction to NASA will guide priorities for the Astrophysics Division and Exoplanet Exploration Program.

3 https://www.nap.edu/catalog/25187/exoplanet-science-strategy 4 https://www.nap.edu/catalog/25252/an-astrobiology-strategy-for-the-search-for-life-in-the-universe 5 https://exoplanets.nasa.gov/exep/NNExplore/EPRV/

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The 2018 Exoplanet Science Strategy report provided “two overarching goals in exoplanet science”:

• to understand the formation and evolution of planetary systems as products of the process of , and characterize and explain the diversity of architectures, planetary compositions, and planetary environments produced by these processes, and

• to learn enough about the properties of exoplanets to identify potentially habitable environments and their frequency, and connect these environments to the planetary systems in which they reside. Furthermore, scientists need to distinguish between the signatures of life and those of nonbiological processes, and search for signatures of life on worlds orbiting other stars

The ESS also provided seven recommendations and thirty five findings. The ESS goals, recommendations, and findings are summarized in Appendix B of the ExEP Science Plan Appendix.

The ExEP science gaps do not appear in a particular order, and by being recognized on this list are deemed important. Currently the gap list is used as a measuring stick when evaluating possible new program activities: if a proposed activity could close a gap, it would be considered for greater priority for Program resources. The ExEP Science Gap List is not meant to provide strategic community guidance on par with a National Academies report (e.g., Decadal Survey, Exoplanet Science Strategy, etc.), but to provide program-level tactical guidance for program management within the evershifting landscape of NASA missions and mission studies. Funding sources outside NASA ExEP are free to make their own judgements as to whether or not to align the work they support with NASA’s Exoplanet Exploration goals. Science gaps directly related to specific missions in phase A-E are relegated to those missions and are not tracked in the ExEP SGL. However, science gaps that facilitate science investigations derived from those missions, or support pre-phase A studies, may appear in the SGL.

Appendix A includes acronyms encountered among the SGL descriptions.

©2021 California Institute of Technology. Government sponsorship acknowledged.

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ID Title Summary Capability Needed Capability Today Mitigation in Progress SCI- Spectral The study of planetary of small A handful of small exoplanets Current and future JWST 01 characterization atmospheres advances exoplanets across a diverse have been identified by RV and proposals to spectrally of atmospheres of our knowledge of range of planet sizes and transit surveys and been pursued characterize small small exoplanets planetary formation and compositions, stellar types, with spectroscopic followup. transiting planets evolution, and can and radiation environments HST and groundbased transit discovered with K2, provide chemical e.g., transit spectroscopy of spectra have provided the first TESS, and ground-based See SPA section evidence for biological small planets transiting cool constraints for these sub- transit surveys. High 6 (atmospheres & processes. There are few dwarf stars, and high- Neptune sized planets, but have dispersion spectroscopy ) extant spectroscopic contrast spectroscopy of marginal sensitivity only coupled with extreme detections of atmospheres small exoplanets orbiting sufficient to detect spectral AO coronagraphy is for small exoplanets solar-type (FGK-type) stars. features in cloud-free H- being developed and may (smaller than Neptune), Temperate examples are of dominated atmospheres. To date provide some detections even though they particular interest. Need TESS has identified ~30 new, of hot planets smaller dominate the exoplanet targets that provide the most small, mostly hot exoplanets than Neptune. The population. The first photons (orbiting nearby, suitable for spectroscopic Roman/CGI instrument constraints are being brightest stars for their followup. So far there are no may be able to spectrally obtained for the class). imaging detections of small characterize atmospheres atmospheric composition Related gaps: limits to exoplanets. of small exoplanets in the of temperate sub-Neptune precision on extracting Cross-Divisional Synergy: Use system. Mission & super-Earth planets, spectra (gap SCI-03), need of time series spectrophotometry concept studies for but detection of definitive for accurate ephemerides for of Earth from NASA EPOXI and Astro2020 have defined spectral features for scheduling spectroscopic DSCOVR missions to simulate capabilities for the next temperate terrestrials is observations (gap SCI-09), time-varying spectra of rocky generation of beyond the current need for precursor surveys exoplanets and test retrieval of observatories to study capability. To remotely to find direct imaging , surface & cloud atmospheres of small assess the frequency of targets (gap SCI-10). variations, etc. (e.g., Jiang et al. exoplanets via transit habitable planets and life 2020, AJ, 156, 26). spectroscopy (e.g., in the , new Origins, LUVOIR, observations and facilities HabEx) or direct imaging must be developed to (e.g., LUVOIR, HabEx, characterize the Roman/Starshade atmospheres of small Rendezvous). exoplanets.

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ID Title Summary Capability Needed Capability Today Mitigation in Progress Cross-Divisional Synergy: PEAS (Planet as Exoplanet Analog Spectrograph; Martin & Skemer 2020 LPICo2195.3006) will observe planets as exoplanets. SCI- Modeling Spectral modeling is Ability to model the Modeling of Ongoing research by the 02 exoplanet essential for inferring the physical and chemical atmospheres accounting for community. ExoPAG atmospheres properties of exoplanet structure of exoplanet varying formation mechanisms, SAG-10 (Cowan et al. atmospheres, identifying atmospheres and their chemistry, 2015, PASP, 127, 311) their most crucial emergent spectra, as a and migration. 3D circulation quantified the needs and See SPA section diagnostics, and defining function of the total models of hot giant planets, expected results from 6 (atmospheres & the design goals for pressure; chemical modeling the impact of transit spectroscopy. biosignatures) future telescopes and composition; presence of nonuniform cloud cover, Cross-Divisional instruments. condensates, clouds & modeling atmospheric chemistry Synergies: NASA hazes; observer phase angle; and escape due to stellar XUV ROSES XRP supports and the radiative and emission and predicted to investigations exploring energetic particle fluxes spectral observations (e.g., HST, the remotely-observable incident from the host star. JWST, future missions, etc.). chemical and physical Understand how the Series of papers on biosignatures processes of exoplanets exchange of matter and papers in June 2018 issue of (including atmospheres). energy with exospheres, Astrobiology. Modeling of NASA Astrobiology lithospheres, hydrospheres, individual target systems (e.g., Program's and potentially biospheres TRAPPIST-1 planets, Proxima Interdisciplinary affect the observed Cen b). Consortia for properties of the Astrobiology Research atmosphere. Challenges (ICAR), the NExSS include determining research coordination composition and properties network, designed to of aerosols, understanding foster interdisciplinary chemistry (e.g., reaction research on aspects of rates, photochemistry, exoplanet atmospheres

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ID Title Summary Capability Needed Capability Today Mitigation in Progress mixing, etc., especially and climate relevant to those relevant to producing life and biosignatures. false positives), NASA PSD's Exobiology radiative transfer modeling ROSES program to (including scattering understand the origin, prescriptions), 3D evolution, distribution, atmosphere dynamics (e.g., and future of life in the general circulation models), universe, including and high-fidelity simulations research on biosignatures of instrumental effects on relevant to spectroscopy the observed spectra. of potentially habitable LUVOIR & HabEx: worlds. Modeling of effects of greenhouse gases for assessment of surface temperatures and stability of surface water (habitability). Origins: Improved modeling of worlds at inner edge of habitable zone, including role of clouds and transport of water vapor. Note: Laboratory measurements of key molecular and aerosol opacities in relevant physical conditions is now covered under gap SCI-13. Exoplanet interior structure and material properties is now covered under gap SCI- 14.

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ID Title Summary Capability Needed Capability Today Mitigation in Progress SCI- Spectral signature Systematic instrumental Ability to reliably extract Community analyses of HST ExoPAG SAG 19 will 03 retrieval and stellar effects in physical parameters, such as transit spectra and of imaging soon complete an timeseries photometry atmospheric pressure- spectra from e.g., GPI & exoplanet imaging data and high contrast images temperature profile and SPHERE. Simple noise models challenge for ground- See SPA section limit the ability to extract abundances of major predict JWST transit spectra and based coronagraphy. The 6 (atmospheres & reliable spectra from atmospheric constituents. coronagraphic spectra. JWST Early Release biosignatures) residual stellar signals. Quantify effects of planet Development of best practices Science Team for transit Key physical parameters and radius over time to acquire exoplanet spectroscopy is planning such as spectral slopes uncertainties on the derived spectra with HST and a data challenge for this and molecular parameters. Thorough application of them to JWST. data type. ExoPAG SAG abundances can be understanding of the limits Studies of contamination by 21 is investigating the uncertain, and achieved of the data, including effects stellar photospheric effect of stellar spectral sensitivity may of correlated and systematic heterogeneities as a limitation to contamination on space- be worse than the photon noise sources. Strategies for extraction of transiting exoplanet based transmission noise limit. Early spectral data taking, calibration, and spectra (e.g., Rackham et al. spectroscopy, and detections have not processing to mitigate these 2018, ApJ, 122, 853), and stellar holding a community withstood reanalysis issues for each individual speckles as a limitation to symposium on the (e.g., Deming & Seager instrument/observatory and extraction of space-based subject (March 2021). 2017, JGRP, 122, 53). compilation of lessons imaging spectra of exoplanets learned for future work. (e.g., Rizzo et al. 2018, SPIE, 10698). Some understanding of the effects of model assumptions on retrieved parameters (Barstow et al. 2020, MNRAS, 493, 4884). Roman Space Telescope Science Investigation Teams have conducted community data challenges for coronagraphic imaging but not spectroscopy.

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ID Title Summary Capability Needed Capability Today Mitigation in Progress SCI- Planetary system Measurements of Integrated exoplanet Ongoing microlensing, RV, Ongoing community 04 architectures: distribution of planetary demographic results from transit, and direct imaging efforts for assessing occurrence rates parameters (e.g., , transit, direct imaging, RV, projects continue to build occurrence rates for for exoplanets of radii, orbital elements) and microlensing surveys. statistics. Examples: Clanton & close-in planets using all sizes from various techniques Include effects of Kepler Gaudi (2016, ApJ, 819, 125) for Kepler, K2, and TESS are important both for DR25, the low yield of demographics of exoplanets on data, reconciling results constraining planet direct imaging detections of wide separation orbits (>2 AU) from different discovery See SPA sections: formation and evolution self-luminous planets, and for M dwarfs. Pascucci et al. methods (e.g., transit, 2 (exoplanet models, and for microlensing results from (2018) study of distribution of radial velocity, popluations), predicting yields of future recent campaigns. Update mass-ratios of planets and their microlensing, direct 3 (exoplanet missions. The lack of periodically to include new stars between microlensing and imaging), and factoring dynamics), integrated exoplanet surveys such as TESS, and transit methods. Meyer et al. in stellar data. 5 (properties of population studies limits to correct the host star (2018, A&A, 612, L3) combined Exoplanet Standard target stars) our understanding of properties used in prior data from RV, microlensing, and Definitions and exoplanet demographics studies. Extend temporal imaging surveys to produce Evaluation Team over a wide range of baselines of RV and transit surface density distribution of (ExSDET) investigating masses and radii. surveys to discover longer- gas giants in 1-10 MJup mass reconciliation of Kepler Extrapolations to HZ period planets. The effect of range for M dwarfs over 0.07- transit results (e.g., demographics need to be measurement uncertainties 400 au. Exoplanet Population ExoPAG13) with radial on best basis (see SCI- on the results must be Observation Simulator (EPOS) velocity survey results. 05). quantified. Practionioners of compares synthetic planet There is a large each technique should make population models to community effort to sufficient occurrence rate observations (Mulders et al. validate TESS exoplanet metadata available for later 2019, ApJ, 887, 157). Fernandes candidates. ExoPAG SIG combined analyses. Planet et al. (2019, AJ, 874, 81) 2 is monitoring available formation and population examine transit, radial velocity, data on exoplanet synthesis models that and direct imaging occurrence occurrence rates. Roman account for the observed rate results to constrain a Space Telescope demographics. Quantify the turnover in the distribution of microlensing survey will impact of stellar binarity on giant planets to between 3-10 au. measure occurrence rates exoplanet frequency, as Improved stellar parameters for the cold planet many potential direct from e.g., Gaia DR2, TIC, population. Cross- imaging target stars are in GALAH, APOGEE, LAMOST, Divisional Synergy: multiple systems. etc. result in improved estimates

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ID Title Summary Capability Needed Capability Today Mitigation in Progress for planet properties and are research on modeling the allowing searches for trends. formation of solar system Moe & Kratter (2020; planets and other small arXiv:1912.01699) review bodies, and on the timing constraints on exoplanet of their formation and frequency as function of stellar migration. binary separation.

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ID Title Summary Capability Needed Capability Today Mitigation in Progress SCI- Occurrence rates Subset of SCI-04 Analysis of occurrence rates Published analyses by several The community is 05 and uncertainties focusing on occurrence taking into account final authors, including (e.g. Burke et actively working on for temperate rates for Earth-sized Kepler data products al. 2015, ApJ, 809, 8; Traub planet occurrence rate rocky planets planets in/near habitable (DR25), including effects of 2016, arXiv:1605.02255; Hsu et studies that incorporate (eta-Earth !⊕) zones (eta-Earth, "⊕), stellar multiplicity, and al. 2019, AJ, 158, 109; Pascucci final Kepler DR25 data which remains improved stellar parameters et al. 2019, ApJ, 883, L15; and Gaia. ExoPAG SIG 2 considerably uncertain. - such that remaining Bryson et al. 2020, AJ, 159, 279; (Exoplanet See SPA sections: Critical to NASA for uncertainties are dominated Kunimoto & Matthews 2020, Demographics) is active, 2 (exoplanet designing a large direct by intrinsic Kepler AJ, 159, 248). Gaia results have NExScI hosted an popluations), imaging mission for systematics. Current improved estimates of radii for Exoplanet Demographics 5 (properties of detecting and estimates rely on transit data all transiting planets (e.g., Fulton conference in Nov 2020. target stars) characterizing Earth (e.g., Kepler). Ideally the & Petigura 2018, AJ, 156, 264; Encourage observations analogs around nearby values would be constrained Berger et al. 2018, ApJ, 866, 99). which can confirm stars and searching for and cross-checked via other ExoPAG SAG 13 final report existence of candidate signs of life. Reducing methods (e.g., PRV), and helped inform mission concept temperate rocky planets uncertainty in "⊕ reduces trends in "⊕ as a function of studies. The most recent in Kepler data upon uncertainty in predicted stellar properties (e.g., star estimates of "⊕ from Bryson et which "⊕ critically yields for imaged and mass, multiplicity, etc.) al. (2020; arXiv:2010.14812) relies. spectrally characterized would be explored to help have 68% confidence limits temperate rocky planets. with target prioritization. spanning 0.16 to 1.5 depending Cross-Divisional Improve knowledge of on assumptions about habitable Synergy: Improve mass-radius relations to zone and extrapolation of understanding of the improve fidelity of completeness for Kepler DR25 evolution of and comparison between transit data. to help inform and PRV surveys. Mission limits on where habitable studies for Astro2020 planets may be found +0.46 adopted "⊕ = 0.24 -0.16 orbiting other stars (i.e., for yield calculations, empirical constraints on informed by SAG 13 (factor habitable zone). of 3 systematic uncertainty). Analysis work that reduces uncertainty in would be beneficial to direct imaging mission concepts.

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ID Title Summary Capability Needed Capability Today Mitigation in Progress SCI- Yield estimation Quantitative non- Capability within NASA Stark et al. (2019, JATIS, Extended mission studies 06 for exoplanet advocate science yield Exoplanet Exploration 024009) presented yield as continue to support direct imaging comparisons made on a Program to independently function of aperture size, improvement in the missions common basis between validate yield estimates telescope type, and astrophysical fidelity of starshade various mission concepts, made by individual mission assumptions. ExEP Standards operational scenarios for both detections and studies, using a transparent Definition and Evaluation Team toward the goal of See SPA section: spectral characterizations. public code implemented (Morgan et al. 2019, approaching idealized 2 (exoplanet Community agreement on independently, and available https://exoplanets.nasa.gov/ mission yields. ExoPAG popluations) key astrophysical input for architecture trades by exep/studies/sdet/) presented SAG 19 is exploring the assumptions (gaps SCI- any NASA-sponsored yield comparisons of individual efficacy of new imaging 05, SCI-11). mission studies. Astro2020 mission architectures for detection metrics (e.g., Decadal Survey decision on multiple spectral characterization Jensen-Clem et al. 2018, the scope & priority of a metrics. Simplified performance AJ 155, 19) via a direct imaging mission will assumptions (coronagraph community data strongly determine the detection metrics, scheduling of challenge and will issue urgency of future work in starshade observations vs. planet its report in 2021. this area. orbital phase and L2 formation- flying dynamics) limits the accuracy of the results. SCI- Intrinsic The accuracies of Improved observational NASA Exoplanet Archive NASA Exoplanet 07 properties of measured exoplanet constraints on exoplanet and contains compilation of Archive is actively known exoplanet parameters needed for host star properties are confirmed and candidate compiling data on host stars planetary characterization needed to help inform the exoplanets and their host stars, exoplanets and their host and interpretation of modeling of exoplanet which can inform mission stars. SAG 22 is See SPA section atmospheric spectra rely atmospheres and concept studies focusing on identifying sets of star 5 (properties of directly on the fidelity of interpretation of exoplanet studying transits or transit properties and data to be target stars) stellar parameters derived spectroscopy (SCI-02). spectroscopy/ photometry of catalogued, maintained, from photometry, Stellar , age, high previously known exoplanets, or improved, and curated spectroscopy, , energy emission (e.g., UV, direct imaging of previously for possible targets for etc. X-rays, flare properties), known exoplanets. Gaia DR2 future exoplanet missions and loss rates, data on exoplanet host star (including previously Improvement of help inform modeling of the properties ingested into Archive. known exoplanetary knowledge of stellar radii evolution of the planet (and Hypatia Catalog Database systems). ExEP plans to its star) and habitability compiles stellar chemical post compiled target list

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ID Title Summary Capability Needed Capability Today Mitigation in Progress is outlined separately in studies. Precision stellar abundance data for thousands of informed by direct SCI-12. abundances inform stars including exoplanet host imaging mission studies exoplanet formation and stars and mission target stars. at NExScI in 2021. interior models. Knowledge CUTE cubesat will of EUV emission informs measure NUV transit models of atmospheric spectroscopy of close-in escape, and measurement of transiting planets to NUV and FUV emission constrain exoplanet informs modeling of mass-loss rates and atmospheric atmospheric photochemistry. For composition. SPARCS terrestrial exoplanet studies cubesat will monitor in the near term, accurate NUV and FUV emission elemental abundances and (and variability) for M ages for M dwarf host stars dwarfs of wide range of are needed but have proved ages. challenging. Basic stellar parameters (e.g., HRD Note: SCI-12 is for position, mass, , improving knowledge of etc.) are needed for non- exoplanet radii exoplanet hosts to enable (especially for statistical studies. Improved deblending the knowledge of planetary contributions from stellar system architecture, companions, both including stellar, substellar, physical and unphysical), or planetary companions, is whereas SCI-07 focusses helpful for interpretation of on improving knowledge exoplanet properties and of other stellar modeling. See ExoPAG parameters to help SAG 17 report for further inform the interpretation discussion on observational and modeling of needs re: stellar exoplanet data (e.g., characterization for TESS spectra). candidates.

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ID Title Summary Capability Needed Capability Today Mitigation in Progress SCI- Mitigating stellar Measurements of masses PRV: Earth orbiting at 1 AU PRV: Smallest claimed RV Major NASA investment 08 jitter as a and orbits are crucial for induces RV semi-amplitude amplitudes detected today are in PRV instrument limitation to characterizing exoplanets, of only ~9 cm/s on the ~0.35 m/s for Tau Ceti (Feng et (NEID) for WIYN sensitivity of and for modeling their (G2V star), and Earth-mass al. 2017, AJ, 154, 135). Single (northern hemisphere 4- dynamical spectra and bulk planet in corresponding HZ measurement precision (SMP) m class). NEID is being methods to detect composition (see ESS p. around a mid-M dwarf star among ongoing RV surveys is commissioned in small temperate 4-30). PRV is currently like (0.12 summarized in Fischer et al. 2020/21 (~0.3 m/s exoplanets and the predominant means of MSun) induces a RV semi- (2016, PASP, 128, 066001) and precision), and data for measure their dynamically measuring amplitude of ~1 m/s updated SOA capabilities were RV standard stars will be masses and orbits masses of exoplanets, and (measurable; e.g., Anglada- presented at EPRV4 workshop made public stellar jitter dominates Escude et al. 2016, Nature, (March 2019). Collier Cameron immediately. Archiving RV uncertainty budget. 536, 437). RV jitter intrinsic et al. (2019, MNRAS, 487, NEID solar data and See SPA sections: Stellar RV “jitter” in its to star is at ~m/s level, and 1082) describes limitations in investigating options to 3 (exoplanet various forms higher for active stars. measuring RV signals at ~0.4 archive EXPRES solar dynamics), (attenuation of convective Requires precision below 10 m/s level in publicly available data. SAG-8 (Plavchan et 5 (properties of blueshift by magnetic cm/s but accuracy at ~cm/s HARPS-N archival solar spectra. al. 2015; arXiv: target stars) activity, granulation, non- level so that systematic Machine learning techniques 1503.01770) discussed radial oscillations, etc.) is errors do not dominate. have shown promise in reducing effective use of the an ever-present source of Major commitments of jitter on simulated and real solar resources needed for noise over a variety of observing time on datasets (de Beurs et al. confirming exoplanets. timescales for both PRV telescopes with PRV arXiv:2011.00003). Astrometry: EXPRES and and astrometric methods. spectrographs needed. Need Studies on stellar astrometric MAROON-X have While PRV is capable of new analysis methods to jitter of stars and the Sun from recently come online. reaching temperate Earth- correct for stellar RV jitter 2000s during development KPF (on Keck) has been mass planets around M using high spectral phases for SIM and Gaia. funded by NSF and will dwarfs, it is not known resolution and broad Existing ground-based be commissioned in whether current limits to spectral coverage. PRV astrometry (CHARA, NPOI, 2022. In response to ESS PRV can be overcome to datasets for the Sun enable VLTI) cannot reach accuracy (2018) recommendation, detect Earth-like planets testing and improvement of required. Gaia is collecting data NASA and NSF orbiting solar-type (FGK) mitigation strategies. that should lead to astrometric chartered Extreme stars. If technological gap Reaching requisite velocity detections of giant exoplanets. Precision Radial Velocity of achieving sub- precision for characterizing Initiative Working Group $arcsecond-level temperate rocky planets for (EPRV WG), which astrometry is achievable, stars hotter than ~F7, and/or provided community

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ID Title Summary Capability Needed Capability Today Mitigation in Progress SCI- and astrometric jitter with high vsini, representing blueprint (Mar. 2020) for 08 could be tens of % of nearby direct agency support of EPRV (cont.) understood/modeled at imaging targets, is even progress through 2020s. sub-$arcsecond-level, more challenging. EPRV WG is writing a then astrometry could Astrometry: Exo-Earth paper summarizing their provide an alternative orbiting 1 MSun star at 10 pc efforts. New NASA method which could yield induces amplitude of ~0.3 ROSES solicitation D.17 orbits and masses for $arcsec. Predicted Extreme Precision Radial rocky planets around astrometric amplitudes for 1 Velocity Foundation nearby stars. Note: MEarth planets at EEID for Science is focused on technology needs for large direct imaging mission science and data analysis EPRV and astrometry are targets within 30 pc range techniques identified as tracked separately in are predominantly between high value by EPRV ExEP Technology Gap 0.1-1 $arcsec. For Sun-like WG, with prospects of List. activity levels, astrometric yielding significant jitter would be ~0.05 advances within 2- $arcsec – small, but not efforts. Cross-Divisional negligible (but higher for Synergy: Observations of more active stars). Develop Sun through Living With capability to perform a Star (LWS) Program of precision astrometry on Heliophysics Division. nearby bright stars as E.g., measurements of precursor or followup for Doppler shifts due to large direct imaging solar oscillations, high mission, as backup to PRV res measurements of for detecting temperate magnetic fields, rocky planets and measuring , etc. with their masses and orbits. Solar Dynamics Observatory (SDO) to provide input for interpreting Sun-as-star solar data to advance EPRV methods.

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ID Title Summary Capability Needed Capability Today Mitigation in Progress SCI- Dynamical Exoplanet candidates There are insufficient Keck HIRES limitation for NASA-NSF Partnership 09 confirmation of detected via various precision RV resources Kepler/K2 exoplanet for Exoplanet exoplanet methods require available to the community confirmation is available time, Observational Research candidates and confirmation and to follow up all K2 and not instrument precision. At 200 (NN-EXPLORE). NASA determination of constraining masses (the TESS candidates that may new Kepler/K2 validations per supported construction of their masses and majority discovered be relevant to spectroscopic year, would need 4 years to NEID instrument, which orbits presently and in near studies with JWST and achieve 50%. For TESS, initial was delivered to WIYN future will be via transit ARIEL. Follow up K2 and screening of science team targets (however commissioning method, e.g., K2, TESS). TESS candidates with quick is ongoing with Magellan/PFS, and starting community See SPA sections: Mass constraints are look low-precision RV HARPS, HARPS-N and access in 2020 has been 2 (exoplanet crucial for understanding screening for false positives ESPRESSO for precise follow- slowed in by closure due populations), atmospheric spectra and (e.g., eclipsing binaries), up at ~1 m/s on the best ~100 to COVID-19). 3 (exoplanet planetary bulk density / then high precision (~1-5 candidates (expect measured Community access dynamics), composition. m/s) to determine masses of masses for only 50). ESPRESSO started in late 2020B. 5 (properties of Ephemerides need to be the best candidates. TESS has demonstrated RV precision NN-EXPLORE is target stars), known precisely enough follow-up requires PRV of ~28 cm/s over a night and ~50 supporting US 6 (atmospheres & to support scheduling of observing time in N and S cm/s over several months for HD community access to biosignatures) transit spectroscopy. hemispheres. Overall, TESS 85512, with instrument precision SMARTS 1.5-m will generate ~15k of ~10 cm/s, and there is CHIRON and candidates of which ~1,250 ESPRESSO-GTO survey of ~50- MINERVA-Australis. should be detected in the 2- 100 K2/TESS planets (<2REarth, NASA supports min cadence data, with ~250 V<14.5; Pepe et al. 2020, community access to smaller than 2 REarth arXiv:2010.00316). MAROON- Keck HIRES and will (Barclay et al. 2018, ApJS, X has recently come online for eventually support access 239, 2). For instruments US community (Gemini-N 8-m). to new Keck KPF with demonstrated <1 m/s TTV: e.g., analysis of Kepler instrument (starting RV accuracy, there is multi-planet systems; Spitzer 2022). Options for limited US community Exploration Program Red additional southern access, and only in northern Worlds campaign observing hemisphere community hemisphere (e.g., NEID, transits over 1000+ hrs for 7- PRV access are being MAROON-X). Modeling of planet TRAPPIST-1 system explored. transit timing variations (Ducrot et al. 2020 A&A, 640, (TTVs) can be used for A112, and in prep TTV transiting multi-planet analysis).

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ID Title Summary Capability Needed Capability Today Mitigation in Progress systems; further observations can improve orbits and masses. Transit epochs need to be known to within a few hours. Queue- based scheduling is needed for Keck RV observations (which will happen with KPF).

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ID Title Summary Capability Needed Capability Today Mitigation in Progress SCI- Precursor Precursor observations Refined target lists Howard & Fulton (2016, PASP, ExoPAG SAG 22 will be 10 observations of benefit future exoplanet consistent with the scope of 128, 4401) completed analysis recommending datasets direct imaging missions by 1) screening the active mission. For the for 2014 versions of WFIRST, needed to complete host targets for close-in, low-mass most likely targets of future Exo-S, and Exo-C target lists star characterization. stellar and substellar direct imaging missions, using data from California planet ExEP Chief Scientists are companions that might assess the detection limits search. Southern target stars are refining the catalog of See SPA sections: compromise exoplanet provided by existing PRV lacking. There are published NASA mission targets 3 (exoplanet imaging sensitivity; 2) data. As detection limits (and unpublished) RV data for (targets identified in dynamics), detecting exoplanets for improve, conduct precision many potential Roman Space studies for direct imaging 5 (properties of future characterization, or RV observing programs in Telescope/CGI targets. Butler et large and probe mission target stars), setting limits on their both N and S hemispheres, al. (2017, AJ, 153, 208) concepts) to motivate 6 (atmospheres & presence; and 3) executed consistently over > published 61k RVs measured community observations biosignatures) Measuring stellar 5 years, towards the goal of over 20 years for stars in Lick- and analysis of these chemical abundances and detecting rocky planets in Carnegie Exoplanet Survey, systems. NEID GTO radiation environments to the target systems and other including many mission targets. program on WIYN is support interpretation of planets that may affect the EPRV Working Group has surveying ~20% of exoplanet spectra (see dynamical stability of their recommend a strategy for a NASA Mission Targets. gap SCI-07). habitable zones. ESA Gaia precursor observing program. EXPRES GTO program mission astrometry (final Facilities: e.g., Keck HIRES, on LDT is surveying data release date TBD) may Lick APF, HARPS-N, HARPS, ~10-15% of NASA reveal evidence of EXPRES, MAROON-X, and Mission Targets. Priority astrometric perturbations by NEID coming online soon. of precursor work on giant exoplanets which Precursor catalogs: The ERPV Roman CGI targets is could be targets for direct Working Group has sorted the unclear due to the imaging. Constraints on imaging mission study targets instrument’s current tech stellar multiplicity from according to each star's demo status. high resolution imaging suitability for extreme-precision needed for assessing Doppler measurements. whether given star is an adequate target for direct imaging (starlight suppression performance is affected by neighboring stars).

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ID Title Summary Capability Needed Capability Today Mitigation in Progress SCI- Understanding is a Statistical knowledge of Images are available showing the The LBTI team is 11 the abundance noise source that exozodiacal dust levels in substructure of cold (Kuiper assessing the cost and and distribution compromises imaging the habitable zone relative to Belt) debris disks as seen by science value of several of exozodiacal and direct spectroscopy the level in our solar system HST, ground adaptive optics, upgrades that would dust of small planets in and is needed for nearby FGK Herschel, and ALMA. Hot dust increase the sensitivity of around the habitable stars that will be the targets emission is detected in many their instrument. Roman zones of nearby stars. of future exoplanet direct systems with near-IR CGI scientists are See SPA section Substructure in the imaging missions. Mission interferometry but its origin and working to quantify what 11 (exozodiacal exozodi distribution may yield simulations of how relevance to habitable zone dust sensitivity their dust) mimic the presence of an exozodi levels and is not understood. There is a rich instrument might be able exoplanet and thus uncertainties affect the literature of theoretical models to achieve to exozodiacal confuse searches made integration times and of structure treating dust in a survey of with smaller telescope achievable signal-to-noise such effects as dust radial nearby stars, should apertures. To date, ratios for exoplanet transport and planetary NASA decide to conduct substructure in the detection and perturbations on debris disk a science program with distribution of habitable characterization, as a structure. The LBTI HOSTS that instrument. Current zone dust has been function of mission survey has measured the mid-IR near-IR interferometers mapped only for the case architecture. Simulations of excess emission due to warm and upcoming ELTs will of our own solar system. scenes as viewed by future exozodiacal dust in the habitable have capabilities to imaging missions, zones of 38 stars (Ertel et al. constrain warm exozodi quantifying the effectiveness 2020, AJ, 159, 177), finding a levels and these are still of multi- observations median exozodi level 3 times being assessed. to discriminate exozodi that of the solar system but with clumps from planets. a significant +1 % uncertainty of Cross-Divisional Directly observed scattered 6 zodis. Detection upper limits Synergy: research on light images of exozodi for individual FGK stars are only interplanetary dust disks in habitable zones ~120 zodis. While the yields of grains, understanding would be very valuable, if exoplanet direct imaging source dust populations they were sensitive down to missions are a weak function of and distribution of dust the ~5 zodi level, were the exozodi level (Stark et al. in solar system. obtained for stars with 2015, ApJ, 808 139), the quality measured 10 $m excess of spectra of Earth analogs can (thus enabling dust become problematic for estimates), and had the telescope apertures < 4-m if the

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ID Title Summary Capability Needed Capability Today Mitigation in Progress resolution to show exozodi level is > +1% from the substructures and validate LBTI median result. Further theoretical simulations. An observational work that reduced understanding of the the uncertainty in the median physical relationship (if any) exozodi level would reduce the between the hot dust risk of marginal spectroscopic emission detected by near- science return by future direct IR interferometers and the imaging missions. warm dust levels in habitable zones. SCI- Measurements of Accurate measurements High resolution imaging in NESSI speckle camera at WIYN, Continued NASA 12 accurate of exoplanet radii are bulk to validate K2 and and Zorro and 'Alopeke cameras support for community transiting planet important for: TESS candidates, at least for on Gemini S and N, respectively, access to speckle radii classification of planets, candidates sufficiently offer ability to screen a subset of cameras on WIYN, estimating their densities, bright and suitable for targets to very small separations. Gemini-N and Gemini-S. modeling compositions, characterization studies or SOAR HRCam (speckle), and Community seeing- See SPA sections: atmospheres, and spectra, demographic studies. For ground-based AO observations limited and high contrast 2 (exoplanet and discovering trends those stars, access to with e.g., Robo-AO, imaging observations populations), important to observatories equipped with Keck/NIRC2, VLT/NACO, etc. supporting TESS follow- 5 (properties of understanding planet AO or speckle imaging have helped validate KOIs and up. Note: SCI-12 is for target stars) formation and evolution. cameras and turnkey TOIs. Gaia DR2 photometry & improving knowledge of The accuracy of pipelines, is needed in both astrometry resolves bright exoplanet radii measured exoplanet radii N and S hemispheres. TESS multiples, and provides (especially for is limited by the accuracy will discover thousands of that have greatly deblending the of measured stellar radii, exoplanet candidates and reduced the uncertainty in contributions from stellar which can be dominated would need to measure >1k intrinsic stellar radii. High companions, both by the effects of blending stars/yr to complete the resolution spectroscopy can physical and unphysical), of light by companion work within a decade. reveal spectroscopic binaries, whereas SCI-07 focusses stars (some of which may Support work that improves and injection and recovery tests on improving knowledge be bound companions). estimation of stellar and can place further quantitative of other stellar Detailed observations are exoplanet parameters for constraints on companions. For parameters to help needed to derive accurate discovered exoplanet improving knowledge of host inform the interpretation stellar radii. The large systems. Supporting star Teff, metallicity, gravity: and modeling of number of TESS photometric and high-res. spectroscopy surveys

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ID Title Summary Capability Needed Capability Today Mitigation in Progress exoplanet candidates and spectroscopic stellar data, (e.g., California-Kepler survey), exoplanet data (e.g., high expected along with astrometric, lower res. Spectroscopy surveys spectra). contamination rates (20˝ photometric, and (e.g., APOGEE & LAMOST), pixels) drives spectroscopic data from and community access to requirement for large latest Gaia data releases, are spectrographs for extracting community effort to critical for accurately stellar spectra (e.g., Keck measure accurate stellar assessing stellar parameters HIRES, NEID, CHIRON, etc.). and exoplanet radii and – and exoplanet radii. For SOA reviewed at “Know Thy assess multiplicity. Not occurrence rate studies, Star – Know Thy Planet” accounting for light accurate limiting radii for Conference in 2017. contamination by planet detection for transit neighboring stars, or poor survey stars for which stellar characterization, transiting planets were not can lead to exoplanet detected is also important. radii systematically See ExoPAG SAG 17 report miscalculated at the tens discussing resource needs % level. TESS (including for TESS follow-up to FFIs) should eventually constrain stellar and generate many more exoplanetary radii. candidates than Kepler, and AO and speckle imaging validation of Kepler prime mission candidates took ~3 years. Note: Improvement in knowledge of other stellar parameters relevant to interpreting exoplanet data is outlined separately in SCI-07.

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ID Title Summary Capability Needed Capability Today Mitigation in Progress SCI- Properties of Understanding and Ability to perform Ab initio line list calculations of Several exoplanet 13 atoms, molecules interpreting the full theoretical calculations of several dozen molecules with the specific efforts to expand and aerosols in gamut of exoplanet key molecular and atomic ability to correct line positions. accuracy and parameter exoplanet spectra with e.g., JWST, spectroscopic properties in Laboratory measurements of line space of line list data atmospheres Roman, ARIEL, and relevant physical conditions lists at low temperatures. (e.g., HITRAN/HITEMP, future missions, will including effects of pressure Reaction rate coefficients Ames, ExoMol, See SPA section 6 hinge on our ability to broadening. Challenges measured at high combustion TheoReTS). Funded (atmospheres & link observations to include obtaining lab temperatures and standard Earth collaboration between biosignatures) theoretical atmosphere measurements or performing temperatures. Publicly available HITRAN/ExoMol and models. These models ab initio calculations of line opacity databases with limited exoplanet theory groups rely on understanding the intensities, line positions, effects of pressure or collisional to develop community optical properties of pressure or collisional broadening. Curated exoplanet tools and best practices atoms, molecules and broadening, and partition aerosol database of refractive for computing and aerosols, as well as the functions. Ability to perform indices (provided by HITRAN) disseminating opacity reaction rates between theoretical calculations over limited wavelength ranges. data. XRP-supported species. Together these and/or laboratory programs on measuring properties shape our measurements of reactions spectroscopic line lists, understanding of the rate coefficients in relevant absorption cross- chemistry and climate of physical conditions. Ability sections, etc. for common exoplanet atmospheres. to obtain refractive indices molecules in of aerosol properties in atmospheres of hot relevant physical conditions. planets and brown dwarfs See white papers by Fortney relevant to impending et al. (2016; arXiv: JWST observations. 1602.06305) and Wolf Savin et al. (2019, BAAS 51, 3, 96).

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ID Title Summary Capability Needed Capability Today Mitigation in Progress SCI- Exoplanet interior Exoplanets exhibit a wide Experimental measurements Facilities to explore Earth- NASA ROSES XRP 14 structure and range of densities beyond and theoretical calculations interior pressures are well- supports investigations to material those seen in the solar of material properties established and exist within an explore the chemical and properties system. Tenuous "super (equations of state and individual institution’s physical processes of puffs", extremely dense transport properties) under laboratory. Ab initio computer exoplanets (including planets (with mean the pressure-temperature simulations exist but not with state and evolution of densities as high as ~12 conditions found in broad application. Only limited surfaces, interiors, and g/cc), and the wide range exoplanets (super-Earths, data exist beyond solar system atmospheres). NExSS of radii observed over the sub-, and cores of planet conditions. Theoretical workshops like mass range of ~2-10 giant exoplanets). modeling of exoplanet interior NExSS/NAI/NSF Joint MEarth pose challenges to Development of dynamic evolution, suite of models across Workshop "Upstairs models of exoplanet compression experiments varying planet density, internal Downstairs: structure, composition, that simulate the pressure heat flux, starting compositions Consequences of Internal formation, and evolution. and temperature conditions (e.g., Thorngren et al. 2016, ApJ, Planet Evolution for the The exploration of in deep interiors. Access to 831, 64; Lopez & Fortney 2014, Habitability and planetary interior and material properties data ApJ, 792, 1; Dorn et al. 2018, Detectability of Life on evolution models is (e.g., phase relationships, ApJ, 865, 20). Extrasolar Planets" hampered by thermodynamic properties) (2016), "Habitable uncertainties in the in an organized format and Worlds 2017: A System measured or numerically- robust modeling tools over a Science Workshop", and predicted material wide range of pressures, NExScI-supported properties under the temperatures, and "Exoplanet relevant physical compositions (e.g., water, Demographics" (2020). conditions, including the ammonia, methane ice, Cross-Agency Synergies: solubility of gases which rock-ice mixtures, Center for Matter at can be exchanged with / etc.). Atomic Pressures the atmosphere. A full Measurements of the (CMAP) is a new NSF understanding of interior miscibility of different Physics Frontier Center structure across the materials at high pressure. designed to connect mass/radius diagram observational and would be valuable for laboratory scientists to interpreting the results of address the high pressure current and future microphysics relevant to exoplanet missions. exoplanetary interiors.

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APPENDIX A: ACRONYM LIST

A&A & Astrophysics AJ Astronomical Journal ALMA Atacama Large Millimeter Array (observatory in Chile) AO Adaptive Optics APD Astrophysics Division APF Automated Planet Finder (robotic 2.4-m optical telescope at ) ApJ Astrophysical Journal ApJS Astrophysical Journal Supplement Series ARIEL Atmospheric Remote-sensing Infrared Exoplanet Large-survey (approved ESA M4 mission targeting 2029 launch) CGI Coronagraph Instrument (on Roman Space Telescope) CHARA Center for High Angular Resolution Astronomy CHIRON CTIO HIgh ResolutiON spectrometer (instrument on CTIO/SMARTS 1.5-m telescope at Cerro Tololo Inter-American Observatory (CTIO), Chile) CMAP Center for Matter at Atomic Pressures CUTE Colorado Ultraviolet Transit Experiment (CubeSat) DR Data Release DSCOVR Deep Space Climate ObserVatoRy EC Executive Committee EEID Earth Equivalent Insolation Distance (EEID; aEEID = √" au where L is stellar luminosity in solar units) ELT Extremely Large Telescope EPOS Exoplanet Population Observation Simulator EPRV Extreme Precision Radial Velocity ERS Early Release Science (JWST program) ESA European Space Agency ESO European Southern Observatory ESPRESSO Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (instrument for ESO VLT observatory) ESS Exoplanet Science Strategy (2018) National Academies Report ExEP Exoplanet Exploration Program Exo-C Exo-Coronagraph (2015 NASA Probe Mission Study) ExoMol Molecular line lists for Exoplanet and other hot atmospheres (database) Exo-S Exo-Starshade (2015 NASA Probe Mission Study) ExoPAG Exoplanet Program Analysis Group ExoSIMS Exoplanet Open-Source Imaging Mission Simulator EXPRES Extreme PREcision Spectrometer (instrument on Lowell Discovery Telescope) ExSDET Exoplanet Standard Definitions and Evaluation Team FFI Full Frame Images FGK Stellar spectral types “F”, “G”, “K” – bracketing stars with “Sun-like” temperatures between about 3900-7200 (Sun is G2 w/temperature 5772K) FUV Far UltraViolet GALAH GALactic Archaeology with HERMES

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GCM General Circulation Model GI Guest Investigator GPI (instrument built for Gemini South 8.1-m telescope) GTO Guaranteed Time Observations HabEx Habitable Exoplanet Imaging Mission HARPS High Accuracy Radial velocity Planet Searcher (instrument on ESO 3.6-m telescope at La Silla) HARPS-N High Accuracy Radial velocity Planet Searcher-North (instrument on Telescopio Nazionale Galileo 3.6-m telescope, La Palma, Canary Islands, Spain) HATNet Hungarian-made Automated Telescope Network HD Henry Draper (star catalog) HERMES High Efficiency and Resolution Multi-Element Spectrograph (instrument on Anglo-Australian Telescope) HIRES High Resolution Echelle Spectrometer (instrument for W. M. Keck Observatory) HITEMP High-TEMPerature molecular spectroscopic database HITRAN HIgh-resolution TRANsmission molecular absorption database HOSTS Hunt for Observable Signatures of Terrestrial Planetary Systems HRCam High-Resolution Camera (speckle instrument on SOAR 4.1-m telescope) HRD Hertzsprung-Russell Diagram HST HZ Habitable Zone ICAR Interdisciplinary Consortia for Astrobiology Research IRTF NASA Infrared Telescope Facility JWST James Webb Space Telescope KELT Kilodegree Extremely Little Telescope KPF Keck Planet Finder (future instrument for W. M. Keck Observatory) JATIS Journal of Astronomical Telescopes, Instruments, and Systems JGRP Journal of Geophysical Research: Planets JPL Jet Propulsion Laboratory JWST James Webb Space Telescope KOI Kepler Object of Interest LAMOST Large Sky Area Multi-Object Fibre Spectroscopic Telescope LBT Large Binocular Telescope LBTI Large Binocular Telescope Interferometer LCOGT Las Cumbres Observatory Global Telescope Network LDT Lowell Discovery Telescope (formerly Discovery Channel Telescope or DCT) LUVOIR Large UV/Optical/IR Surveyor LWS Living With a Star (NASA Heliophysics program) MAROON-X Magellan Advanced Radial velocity Observer of Neighboring eXoplanets (instrument on Gemini-North telescope) MINERVA-Australis Miniature Exoplanet Radial Velocity Array – Australis (observatory at Mt. Kent Observatory, Queensland, Australia) MNRAS Monthly Notices of the Royal Astronomical Society NACO Nasmyth Adaptive Optics System (instrument for VLT observatory) NAI NASA Astrobiology Institute

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NASA National Aeronautics and Space Administration NEID NN-Explore Exoplanet Investigations with Doppler spectroscopy (pronounced ‘noo-id’ – derived from the word meaning ‘to see’ in native language of the Tohono O’odham, on whose land Kitt Peak National Observatory is located) NESSI NASA Exoplanet Star (and) Speckle Imager (instrument for Palomar 5-m telescope) NExScI NASA Exoplanet Science Institute NExSS Nexus for Exoplanet System Science NIRC2 Near InfraRed Camera 2 (instrument for W.M. Keck Observatory) NN-EXPLORE NASA-NSF EXoPLanet Observational Research NOIRLab National Optical- Research Laboratory (NSF center) NPOI Navy Precision Optical Interferometer NSF National Science Foundation NUV Near UltraViolet PASP Publications of the Astronomical Society of the Pacific PEAS Planet as Exoplanet Analog Spectrograph PFS Carnegie Planetary Finder Spectrograph (instrument on Magellan II 6.5-m telescope) PRV Precision Radial Velocity PSD Planetary Science Division PTF Palomar Transient Factory RCN Research Coordination Network Robo-AO Robotic-Adaptic Optics (instrument now on U. Hawai’i 2.2-m telescope) ROSES Research Opportunities in Space and Earth Science RV Radial Velocity SAG Science Analysis Group SDO Solar Dynamics Observatory SGL Science Gap List SIG Science Interest Group SIT Science Investigation Team SMARTS Small & Moderate Aperture Research Telescope System (consortium operating telescopes on Cerro Tololo, Chile, including CTIO/SMARTS 1.5-m telescope) SMD Science Mission Directorate SMP Single Measurement Precision SOA State Of the Art SOAR SOuthern Astrophysical Research (4.1-m telescope at Cerro Pachon, Chile) SPA Science Plan Appendix SPARCS Star-Planet Activity Research CubeSat SPHERE Spectro-Polarimetric High-contrast Exoplanet REsearch (instrument on VLT) SPIE Society of Photo-Optical Instrumentation Engineers STDT Science and Technology Definition Team TBD To Be Determined TESS Transiting Exoplanet Survey Satellite TheoReTS Theoretical Reims-Tomsk Spectral data (database) TIC TESS Input Catalog

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TOI TESS Object of Interest TPF Finder TRAPPIST Transiting Planets and Small Telescope TTV Transit Timing Variations UV UltraViolet VLT Very Large Telescope VLTI Very Large Telescope Interferometer WASP Wide Angle Search for Planets WG Working Group WIYN Wisconsin, Indiana, Yale, NOAO Observatory WFIRST Wide-Field Infrared Survey Telescope (previous name for Nancy Grace Roman Space Telescope or Roman Space Telescope for short) XRP eXoplanet Research Program (an element of the NASA Research Opportunities in Space and Earth Sciences (ROSES) program) XUV X-ray and Ultraviolet

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