{
  "abstract": "The European Space Agency’s Ariel mission will conduct a survey of the atmospheric properties of exoplanets around bright stars. The mission is nominally divided into three tiers. The Tier 1 survey will consist of low-precision observations of ∼1000 planets, with a subset of these included in the higher-precision Tier 2 survey expected to be necessary for atmospheric characterization. Tier 3 will be repeated observations of a small number of benchmark planets. Though previous studies have assessed the ability of Ariel to uncover population-level trends, they have generally presupposed a given tier. Here we interrogate this assumption and assess the information content of Ariel transmission spectra as a function of tier for three benchmark planets: a hot-Saturn, warm-Neptune, and temperate sub-Neptune. We simulate a grid of Ariel transit spectra at different Tiers for each target and use retrievals to assess which chemical species are well constrained. We find that for giant planets like a hot-Saturn or warm-Neptune, Tier 1 quality observations are sufficient for ≲1.5 dex constraints on H ₂ O and CO ₂ , even in the presence of grey clouds—meaning important chemical insights are already obtainable in the Tier 1 survey. Moving to Tiers 2 and 3 results in an incremental increase in precision as well as other molecules becoming constrainable in certain scenarios (e.g., H ₂ S, CO). Tier 1 observations are also sufficient to identify CH ₄ in a temperate sub-Neptune, whereas observations with at least Tier 2 precision are necessary for CO ₂ . The number of transits necessary to reach this observational S/N, however, may be prohibitive for the inclusion of temperate sub-Neptunes in even the Tier 1 survey.",
  "abstract_shown": true,
  "affiliations": [
    "University of Chicago",
    "Institut Trottier de Recherche sur les Exoplanètes",
    "McGill University",
    "McMaster University",
    "Cornell University"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 4,
  "authors": [
    {
      "affs": [
        0,
        1
      ],
      "name": "Michael Radica",
      "orcid": "0000-0002-3328-1203"
    },
    {
      "affs": [
        1,
        2
      ],
      "name": "Nicolas B. Cowan",
      "orcid": "0000-0001-6129-5699"
    },
    {
      "affs": [
        3
      ],
      "name": "Ryan Cloutier",
      "orcid": "0000-0001-5383-9393"
    },
    {
      "affs": [
        3,
        4
      ],
      "name": "Leo Yang Wang",
      "orcid": "0009-0009-3021-6156"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/80qc00drbpr71.bib",
  "cited_by": 0,
  "doi": "10.3847/1538-3881/aea56d",
  "fulltext_url": null,
  "id": "80qc00drbpr71",
  "issns": [
    "0004-6256",
    "1538-3881"
  ],
  "landing_url": "https://iopscience.iop.org/article/10.3847/1538-3881/aea56d",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "3103|Stellar, planetary, and galactic studies"
    ]
  ],
  "openalex": "W7153132141",
  "pdf_url": "https://iopscience.iop.org/article/10.3847/1538-3881/aea56d/pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-13",
  "publisher": "American Astronomical Society",
  "ris": "https://research.draconitic.com/paper/80qc00drbpr71.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:14Z",
      "native_id": "10.3847/1538-3881/aea56d",
      "source": "crossref",
      "url": "https://iopscience.iop.org/article/10.3847/1538-3881/aea56d"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "openalex:3103|Stellar, planetary, and galactic studies",
      "subfield": "stellar"
    }
  ],
  "title": "On the Information Content of Ariel Transmission Spectra: Reassessing the Tier System",
  "title_text": "On the Information Content of Ariel Transmission Spectra: Reassessing the Tier System",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:18:14Z",
  "url": "https://research.draconitic.com/paper/80qc00drbpr71",
  "venue": "The Astronomical Journal",
  "versions": []
}