{
  "property": "Ephemeris, https://theephemeris.vercel.app",
  "compiled": "2026-10-06",
  "sources": [
    {
      "use": "Orbital elements: the two-line element sets every pass is computed from",
      "citation": "CelesTrak (T. S. Kelso), GP element sets, GROUP=visual and GROUP=stations, FORMAT=tle",
      "url": "https://celestrak.org/NORAD/elements/gp.php?GROUP=visual&FORMAT=tle",
      "also": "https://celestrak.org/NORAD/elements/gp.php?GROUP=stations&FORMAT=tle",
      "retrieved": "2026-10-06T06:58:23Z (the bundled snapshot); the page fetches fresh sets in the browser at most once an hour",
      "rights": "Public orbital data published by CelesTrak; no licence terms are stated on the endpoint. Credited as 'Orbital elements: CelesTrak' on the page and on every Pass Card. The endpoint answers with Access-Control-Allow-Origin: * (checked 2026-10-06)."
    },
    {
      "use": "The propagation model, and the verification ephemerides the tests compare against",
      "citation": "D. A. Vallado, P. Crawford, R. Hujsak and T. S. Kelso, 'Revisiting Spacetrack Report #3', AIAA 2006-6753, AIAA/AAS Astrodynamics Specialist Conference, 2006",
      "url": "https://celestrak.org/publications/AIAA/2006-6753/",
      "retrieved": "2026-10-06 (AIAA-2006-6753.zip: SGP4-VER.TLE and the C++ verification outputs for 00005, 06251, 28057, 28350, 08195)",
      "rights": "Published paper; the verification files are used as test fixtures only (test/fixtures/vallado) and are not deployed."
    },
    {
      "use": "The element set format and the original model",
      "citation": "F. R. Hoots and R. L. Roehrich, 'Spacetrack Report No. 3: Models for Propagation of NORAD Element Sets', Aerospace Defense Command, December 1980",
      "url": "https://celestrak.org/NORAD/documentation/spacetrk.pdf",
      "retrieved": "cited, not reproduced",
      "rights": "US government report, approved for public release."
    },
    {
      "use": "SGP4/SDP4 implementation",
      "citation": "satellite.js 7.1.0 (Shashwat Kandadai and contributors), a port of Vallado's SGP4",
      "url": "https://www.npmjs.com/package/satellite.js",
      "retrieved": "2026-10-05 (npm)",
      "rights": "MIT licence."
    },
    {
      "use": "Sidereal time (equation 12.4), the Sun (chapter 25), refraction near the horizon (chapter 16), and the worked examples 12.a, 12.b and 25.a the tests reproduce",
      "citation": "J. Meeus, Astronomical Algorithms, 2nd edition, Willmann-Bell, 1998, ISBN 0-943396-61-1",
      "url": null,
      "retrieved": "cited from the book; the code is copied from github/almucantar/src/astro (same author, MIT), which implements it",
      "rights": "Formulas and published example values are cited; no text is reproduced."
    },
    {
      "use": "Standard magnitudes (1000 km range, 50% illuminated) for 13 objects",
      "citation": "Heavens-Above (Chris Peat), satellite information pages",
      "url": "https://www.heavens-above.com/SatInfo.aspx?satid=25544",
      "retrieved": "2026-10-06, one page per object: 25544, 48274, 59588, 20580, 694, 25994, 10967, 16182, 27386, 16908, 61047, 27424, 21574",
      "rights": "Thirteen numbers used as facts with credit; no page content reproduced."
    },
    {
      "use": "The brightness comparison: Sirius at visual magnitude −1.46",
      "citation": "D. Hoffleit and W. H. Warren Jr., The Bright Star Catalogue, 5th revised edition (Yale University Observatory, 1991), HR 2491",
      "url": "https://cdsarc.cds.unistra.fr/viz-bin/cat/V/50",
      "retrieved": "cited value",
      "rights": "Published catalogue value."
    },
    {
      "use": "Coastlines on the ground-track map",
      "citation": "Natural Earth, 1:110m coastline (ne_110m_coastline), rounded to 0.1°",
      "url": "https://raw.githubusercontent.com/nvkelso/natural-earth-vector/master/geojson/ne_110m_coastline.geojson",
      "retrieved": "2026-10-06",
      "rights": "Public domain (https://www.naturalearthdata.com/about/terms-of-use/)."
    },
    {
      "use": "The 74 cities, their coordinates and their time zones",
      "citation": "IANA Time Zone Database, zone.tab: each zone's principal location",
      "url": "https://raw.githubusercontent.com/eggert/tz/main/zone.tab",
      "retrieved": "2026-10-06",
      "rights": "Public domain."
    },
    {
      "use": "The OKLCH to sRGB conversion the canvases use",
      "citation": "B. Ottosson, 'A perceptual color space for image processing', 2020",
      "url": "https://bottosson.github.io/posts/oklab/",
      "retrieved": "cited, matrices transcribed",
      "rights": "Published method."
    },
    {
      "use": "Typefaces",
      "citation": "Unbounded (NaN), Onest (Dmitri Voloshin), Martian Mono (Evil Martians), self-hosted through the @fontsource-variable packages",
      "url": "https://fontsource.org",
      "retrieved": "2026-10-05 (npm)",
      "rights": "SIL Open Font Licence 1.1."
    }
  ]
}