{
  "sources": [
    {
      "id": "vsop87d",
      "what": "The planets and the Sun: heliocentric longitude, latitude and radius of Mercury to Neptune and the Earth, mean ecliptic and equinox of date",
      "source": "VSOP87D, P. Bretagnon and G. Francou, Astronomy & Astrophysics 202, 309 (1988)",
      "url": "https://cdsarc.cds.unistra.fr/ftp/VI/81/",
      "licence": "Published scientific data, distributed by the CDS (Strasbourg) for scientific use; cited, not modified except for truncation",
      "retrieved": "2026-10-10",
      "vendored": "src/natal/vsop87d.json",
      "note": "Terms whose largest contribution between 1800 and 2200 is under 2e-7 (rad or AU) are dropped; the cost, measured against the full series at 401 dates, is in the file's \"truncation\" field."
    },
    {
      "id": "geonames",
      "what": "The towns offered by name: 34,156 places of 15,000 people or more, with latitude, longitude and IANA time zone",
      "source": "GeoNames geographical database, cities15000 extract",
      "url": "https://download.geonames.org/export/dump/",
      "licence": "Creative Commons Attribution 4.0 (CC BY 4.0); credited on the page and in the method note",
      "retrieved": "2026-10-10",
      "vendored": "public/towns.json",
      "note": "Names outside the print font's letters are replaced by GeoNames' ASCII form; coordinates rounded to 0.0001°."
    },
    {
      "id": "horizons",
      "what": "The check: apparent geocentric ecliptic longitude and latitude of date for the Sun, the Moon and Mercury to Neptune at eight moments, 1930 to 2026, and their longitude at 2263 more, every 53,701 minutes from 1800 to 2030",
      "source": "JPL Horizons system, Solar System Dynamics Group, Jet Propulsion Laboratory; quantity 31, observer 500@399, times UT",
      "url": "https://ssd-api.jpl.nasa.gov/doc/horizons.html",
      "licence": "Public data from a NASA/JPL service; cited as the source of the comparison figures",
      "retrieved": "2026-10-10",
      "vendored": "test/fixtures/horizons.json and test/fixtures/horizons-survey.json (with every query string)"
    }
  ]
}