Ariel data: spectroscopic databases

Ariel Spectroscopic Data and Databases Working Group

Expert spectroscopic support for the ESA Ariel mission and the wider exoplanet community.

We coordinate the provision of spectroscopic data for the ESA Ariel mission, acting as an interface between the exoplanet modelling community and laboratory/theoretical spectroscopists.

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About the Working Group

The Ariel Spectroscopic Data and Databases Working Group (WG) brings together experts in molecular and atomic spectroscopy, laboratory astrophysics, and atmospheric modelling.

Our goals are to:

• Identify and provide spectroscopic data needed for the Ariel space mission and related exoplanet atmosphere studies.
• Serve as an expert contact point for questions on data availability, quality, and coverage.
• Coordinate with data producers (laboratory and theoretical groups) and users (retrieval and modelling teams) to close gaps in available data.
• Maintain a transparent, community-visible workflow via GitHub.

This GitHub organisation, Ariel-data, is the central hub for communication between data providers and data users.

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Working Group Members

The WG brings together experts in:

• Molecular and atomic spectroscopy
• Laboratory astrophysics
• Theoretical quantum chemistry and nuclear motion calculations
• Atmospheric modelling and retrievals
• Data curation and database development

A list of WG members, their affiliations, expertise, and contacts organised by their expert fields

Coordinators

• Katy Chubb, Bristol
• Severine Robert, BIRA-IASB
• Clara Sousa Silva, Bard
• Sergey Yurchenko, UCL

Molecular and atomic data

• Vincent Boudon, CNRS
• Aleksandra Foltynowicz Matyba, UMU
• Isabelle Kleiner, LISA CNRS
• Michaël Rey, Université de Reims Champagne-Ardenne
• Cyril Richard, CNRS
• Ibrahim Sadiek, Leibniz Institute for Plasma Science and Technology
• Stefania Stefani, IAPS-INAF
• Jonathan Tennyson, UCL
• Karan Molaverdikhani, Ludwig-Maximilians-Universität München

Molecular and atomic broadening data

• Nicole F. Allard, Observatoire de Paris,
• Jeanna Buldyreva, Université Bourgogne Franche-Comté
• Andrei Sokolov, UCL

Collision induced absorption and continuum data

• Tijs Karman, Radboud University

Atmospheric Chemistry

• Olivia Venot, Université Paris Cité and Univ Paris Est Creteil

UV Photodissociation / photoabsorption data

• Helgi Rafn Hrodmarsson, CNRS

Databases and data standards

• Iouli E. Gordon, HITRAN, CfA
• Robert J. Hargreaves, HITRAN, CfA
• Christian Hill, International Atomic Energy Agency

Sinergy with the users

• Benjamin Bultel, Université Paris-Saclay
• Athena Coustenis, LESIA, Paris Observatory
• Christiane Helling, Space Research Institute
• Helena Lecoq-Molinos, TU Graz
• Alessandra Miglio, IAPS-INAF
• Joanna K. Barstow, The Open University
• Patrick Gerard Joseph Irwin, University of Oxford
• David A. Lewis, Space Research Institute
• Giovanna Rinaldi, IAPS-INAF
• Tim A. van Kempen, SRON Netherlands Institute for Space Research

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Spectroscopic Data We Support

We focus on data for molecules and atoms relevant to exoplanet atmospheres, particularly those targeted by Ariel and other current/future missions.

Spectroscopic data products

• Molecular and atomic line lists
• Opacities
• Temperature- and pressure-dependent cross sections
• Line broadening parameters
• Transition probabilities
• k-tables
• Oscillator strengths

Continuum and photoprocesses

• Collision-induced absorption (CIA), including temperature and pressure dependence
• Photodissociation cross sections

Particles and chemistry

• Optical properties of particles (aerosols, condensates, hazes)
• Chemical reaction rate coefficients and related atmospheric chemistry data

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How to Request Data or Ask Questions

We use GitHub Issues in category-specific repositories so that requests and discussions are:

• Traceable
• Publicly visible to the wider spectroscopic community
• Easy to follow up by WG members

Step-by-step

1. Go to the Ariel-data organisation.
2. Choose the repository that best matches your request (see list below).
3. Click the Issues tab.
4. Click New issue and provide:
   • Target molecule(s) or atom(s)
   • Spectral range and resolution
   • Temperature and pressure range
   • Type of data (e.g. line list, CIA, broadening, photodissociation, aerosols, chemistry)
   • Intended application (e.g. forward model, retrievals, specific mission/instrument)
5. Submit the issue.
   A WG member will pick it up, coordinate a response and, where needed, reach out to colleagues in the spectroscopic community.

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Repositories and Data Categories

The WG maintains several category-specific repositories. Each repository contains links, documentation, and notes on data availability, quality, and open issues.

• broadening
  Pressure broadening, line-shape parameters, and related line profile information.

• Databases
  Overview of major spectroscopic databases, pointers to relevant entries for Ariel and exoplanet applications.

• aerosols
  Optical properties (e.g. refractive indices, single-scattering properties) of particles, condensates, and hazes.

• linelists
  Molecular and atomic line lists, transition probabilities, oscillator strengths, and related spectroscopic data.

• atmochemistry
  Chemical networks, rate coefficients, and other reaction data relevant for exoplanet atmospheres.

• opacities
  Opacity tables, temperature- and pressure-dependent cross sections, k-tables, and related pre-computed products.

• HITRAN
  Information and guidance on using HITRAN and related compilations in the context of Ariel and exoplanet studies.

• CIA
  Collision-induced absorption (CIA) data, including temperature and pressure dependent cross sections.

• UV-cross-sections
  UV and photodissociation cross sections for molecules important in exoplanet atmospheres.

• General
  Cross-cutting information, coordination notes, general documentation, and topics that do not fit in a single category.

We encourage data users and providers to follow or watch the relevant repositories and to contribute via issues and pull requests.

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Connection to Ariel and the White Paper

This WG operates within the ESA Ariel Consortium to ensure that the mission’s spectroscopic data needs are met and documented.

Many of the assessments and links collected here are based on our recent white paper:

Data availability and requirements relevant for the Ariel space mission and other exoplanet atmosphere applications
RASTI 3, 636–690 (2024)
DOI: 10.1093/rasti/rzae039

We aim to keep this GitHub space up to date and complementary to the white paper, reflecting new data, updates, and community input.

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Acknowledgements

We acknowledge support from the ESA Ariel mission and the wider exoplanet spectroscopy community.
Please follow the citation and acknowledgement guidance in the relevant repositories and in the white paper when using data coordinated by this WG.