{
  "version": "v1",
  "calendar_year": 2027,
  "calculation": "ten-minute midpoint integration",
  "night_definition": "local noon to next local noon, labelled by start date",
  "altitudes": "apparent topocentric body centres, no atmospheric refraction; level horizon and unspecified elevation",
  "sun_thresholds_deg": [
    -6,
    -12,
    -18
  ],
  "moon_horizon_deg": 0,
  "timezones": {
    "fairbanks": "America/Anchorage",
    "yellowknife": "America/Yellowknife",
    "reykjavik": "Atlantic/Reykjavik",
    "tromso": "Europe/Oslo",
    "rovaniemi": "Europe/Helsinki",
    "abisko": "Europe/Stockholm",
    "hobart": "Australia/Hobart",
    "queenstown": "Pacific/Auckland"
  },
  "source_files": {
    "city_input": "city-aacgm-inputs.v1.json",
    "city_input_sha256": "dd9a8cfea6bc108c09739378287a1e932a181b4d02bb09c713f469306278fced"
  },
  "ephemeris": {
    "url": "https://ssd.jpl.nasa.gov/ftp/eph/planets/bsp/de440s.bsp",
    "file": "de440s.bsp",
    "sha256": "c1c7feeab882263fc493a9d5a5b2ddd71b54826cdf65d8d17a76126b260a49f2"
  },
  "software": {
    "python": "3.14.9",
    "skyfield": "1.55",
    "matplotlib": "3.11.2"
  },
  "validation": {
    "daily_rows": 2920,
    "monthly_rows": 96,
    "expected_daily_rows": 2920,
    "expected_monthly_rows": 96,
    "checks": "0<=moon_below<=astronomical<=nautical<=civil<=night duration; all passed"
  },
  "limitations": "No clouds, terrain, light pollution, auroral activity or visibility probability. A ten-minute midpoint grid resolves each threshold crossing only to approximately one grid interval."
}