{
 "v": 1,
 "fetched": "2026-10-11",
 "items": [
  {
   "id": "cassini-iss-global-maps",
   "name": "Cassini ISS Global Maps of Jupiter and Saturn: Saturn RGB global colour map, original and contrast-enhanced (2011-08-11)",
   "url": "https://atmos.nmsu.edu/PDS/data/PDS4/co_iss_global-maps/data_derived/Cassini_ISS_RGB_Saturn_global_color_map_original.fits",
   "credit": "Li, L., West, R., Jiang, X., Knowles, B. (2023), Cassini ISS Global Maps of Jupiter and Saturn Bundle, NASA PDS Atmospheres Node, DOI 10.17189/rkkb-6y30; Cassini Imaging Science Subsystem (NASA / JPL / Space Science Institute)",
   "licence": "Public domain / open data (NASA Planetary Data System archive; no copyright asserted; credit as requested)",
   "fetched": "2026-10-11",
   "transform": "FITS float32 big-endian, 3601 x 1801 x 3, 0.1 deg per pixel, planetocentric latitude, WEST longitude 360 -> 0 left to right, average 161 km per pixel (so the 4K map is about 1.1x oversampled and an 8K map would add no detail: no color-8k files are shipped). Row order is north first (the FITS header says -90:0.1:90 but the data and the PDS browse PNG run +90 first). East longitude = 0.1 x column, so the image is rolled 1800 columns to put -180 E at x = 0; the duplicated 360 W column is dropped. The source has no data beyond 78.9 N, in a thin seam at the equator, between 5.3 S and 17.2 S (hidden behind the rings in the Cassini frames) and beyond 82 S: about 18 percent of the map. The strip 0.7 N to 5.7 S that does have data is also dropped because it is in the baked-in shadow of the rings (the engine casts its own ring shadow). Those rows are invented fill: linear interpolation in latitude between smoothed edge rows plus mirrored high-pass texture, and for the polar caps the edge-row colour with a 7 percent darkening toward the pole and fading mirrored texture; the north polar hexagon and the south polar vortex are NOT in the map. Natural colour: hue/chroma from the original map (smoothed 2 px), luminance = half original, half contrast-enhanced product (structure), scaled to mean 192 with gain 1.7. No other tone transform. 4K is a bicubic resample, 2K an area resample of the 1800-row map. The cloud map has no physical longitude anchor and simply rotates with W.",
   "used": [
    "assets/tex/color-2k.jpg",
    "assets/tex/color-4k.webp",
    "assets/tex/color-4k.jpg",
    "assets/fallback/map-2k.jpg",
    "assets/fallback/poster.jpg",
    "assets/og.jpg"
   ]
  },
  {
   "id": "rss-rev007e",
   "name": "Cassini RSS ring occultation Rev007E, X-band (DSS-43), calibrated normal optical depth profile TAU_10KM (CORSS_8001 v2.0)",
   "url": "https://pds-rings.seti.org/holdings/volumes/CORSS_8xxx/CORSS_8001/data/Rev007/Rev007E/Rev007E_RSS_2005_123_X43_E/RSS_2005_123_X43_E_TAU_10KM.TAB",
   "credit": "Cassini Radio Science Subsystem team; NASA PDS Ring-Moon Systems Node (SETI Institute). Data set CO-SR-RSS-4/5-OCC-V2.0",
   "licence": "Public domain / open data (NASA Planetary Data System archive; no copyright asserted; credit as requested)",
   "fetched": "2026-10-11",
   "transform": "ASCII table, 28,888 rows at 2.5 km sampling, ring radius 72,771 to 144,989 km (the \"10KM\" in the name is the reconstruction resolution). Radius used = RING RADIUS + RADIUS CORRECTION DUE TO IMPROVED POLE + RADIUS CORRECTION DUE TO TIMING OFFSET (column 1+2+3). NORMAL OPTICAL DEPTH is column 7; the instrument threshold is about 5.0 (column 9) so tau is clipped to 5, which is also the CONTRACT limit. A noise floor of 0.003 is subtracted (the radio profile has about +-0.003 noise at 2.5 km) and negatives are clipped to 0, so empty gaps and the Roche Division are exactly 0 in the strip. Linear interpolation onto a 0.5 km grid, then box-averaged (area average of the cumulative integral) into each strip texel; A = sqrt(min(tau, 5) / 5). One longitude only (egress, ring longitude about 248 to 256 deg), so eccentric features (B ring outer edge at about 117,645 km here, Titan and Maxwell ringlets, F ring) sit at their position in this cut, within about 10 to 80 km of the circular mean radii in rings.json. Gap edges in the profile agree with the PDS table within 10 km (Encke 133,431..133,739 vs 133,423..133,745; Keeler 136,491..136,516 vs 136,487..136,522; Herschel 118,196..118,279 vs 118,188..118,284). Radius accuracy of the texture: about 1 texel at 8K (9 km) for sharp features, worse for eccentric ones.",
   "used": [
    "assets/tex/ring-main-2k.png",
    "assets/tex/ring-main-8k.png"
   ]
  },
  {
   "id": "uvis-stellar-occultations",
   "name": "Cassini UVIS stellar occultation ring profiles (COUVIS_8001 v3.0, TAU10KM tables, 275 files)",
   "url": "https://pds-rings.seti.org/holdings/volumes/COUVIS_8xxx/COUVIS_8001/data/",
   "credit": "Cassini UVIS team; Colwell, J. E. et al. (2010), Astron. J. 140, 1569-1578, DOI 10.1088/0004-6256/140/6/1569; NASA PDS Ring-Moon Systems Node",
   "licence": "Public domain / open data (NASA Planetary Data System archive; no copyright asserted; credit as requested)",
   "fetched": "2026-10-11",
   "transform": "Two uses. (1) D ring: 24 profiles that cover 66,000 to 76,000 km were combined with a 30 percent trimmed mean and the D ring optical depth came out below 0.003 everywhere, i.e. below the noise of the data (the PDS table gives 1e-5 to 1e-3). The strip therefore carries a smooth DISPLAY profile that is NOT measured: floor 0.004 and two Gaussians (sigma 25 km, +0.008) at the ringlet radii 67,580 and 71,710 km listed in the PDS table, ramped in over the first 150 km, replacing the RSS profile below 73,000 km (blended to 74,300 km). Amplitude is non-physical, radii are physical. (2) F ring: the RSS cut does not intersect the F ring core, so the 53 UVIS profiles with a clear peak (smoothed tau 0.15 to 3 within 139,826..140,612 km) were each re-centred on their own peak and the median profile (core tau about 0.27, 10 km bins) was added to the strip centred on the F ring core radius a = 140,224 km. The F ring is therefore a circular representative core, not a measured cut.",
   "used": [
    "assets/tex/ring-main-2k.png",
    "assets/tex/ring-main-8k.png"
   ]
  },
  {
   "id": "rmsn-ring-table",
   "name": "PDS Ring-Moon Systems Node, Vital Statistics for Saturn's Rings; IAU Gazetteer of Planetary Nomenclature, Ring and Ring Gap Nomenclature (WGPSN)",
   "url": "https://pds-rings.seti.org/saturn/saturn_rings_table.html",
   "credit": "SETI Institute / NASA PDS Ring-Moon Systems Node (after Colwell et al. 2009, Nicholson et al. 2014, French et al. 2016, 2017); IAU WGPSN / USGS Astrogeology, https://planetarynames.wr.usgs.gov/Page/Rings",
   "licence": "Public domain / open data (NASA Planetary Data System archive; no copyright asserted; credit as requested)",
   "fetched": "2026-10-11",
   "transform": "Inner/outer radii of every item in rings.json are the PDS table values (Cassini era). The IAU table agrees for rings and gaps except where it quotes a single centre radius. Differences from older reference tables: the A ring inner edge is 122,050 km (older tables: 122,170), the B ring outer edge 117,570 km (older: 117,580; the PDS table lists the Cassini Division and Huygens Gap from 117,500, an overlap of 70 km that reflects the variable B ring edge), the F ring is given as its swath 139,826..140,612 km around the core at 140,224 km (not 140,180 km). Arc and Pallene ring radii are single values in the table: the arcs carry a nominal 100 km band (Aegaeon arc 250 km) marked \"approx\" in the text. Ringlet names follow the PDS table; the IAU Gazetteer lists no named ringlets. Descriptions, notable text and \"named for\" lines are written for this page; shepherd-moon and resonance facts come from the PDS table comments and standard references.",
   "used": [
    "data/rings.json"
   ]
  },
  {
   "id": "saturn-facts",
   "name": "NASA NSSDC Saturn fact sheet; NASA Science Saturn moons page (JPL SSD, 293 confirmed moons as of August 2026); IAU WGCCRE 2015; Iess et al. 2019; Mankovich et al. 2019",
   "url": "https://nssdc.gsfc.nasa.gov/planetary/factsheet/saturnfact.html",
   "credit": "NASA / GSFC NSSDC; NASA Science (https://science.nasa.gov/saturn/moons/); Iess et al. 2019, Science 364, eaat2965; Mankovich et al. 2019, ApJ 871, 1",
   "licence": "Facts; citations only",
   "fetched": "2026-10-11",
   "transform": "Equatorial radius 60,268 km and polar radius 54,364 km at the 1 bar level, mass 5.6832e26 kg, density 687 kg/m3, sidereal year 10,755.7 d = 29.447 yr, obliquity 26.73 deg. System III day 10 h 39 min 22.4 s from the IAU WGCCRE rate 810.7939024 deg/d. Ring-seismology rotation 10 h 33 min 38 s (Mankovich et al. 2019). Moon count 293: the 2023 and March 2025 batches took it to 274, a further 11 were announced by the Minor Planet Center in March 2026 (285) and NASA lists 293 as of August 2026; the number keeps growing. Ring mass about 1.5e19 kg (0.41 Mimas masses, Iess et al. 2019). Ring system diameter 2 x 140,224 km (F ring core) = 280,450 km.",
   "used": [
    "data/saturn.json"
   ]
  },
  {
   "id": "ring-colour-and-faint-rings",
   "name": "Hand-set ring colour ramp and artistic faint-ring opacity (ring-faint-1k)",
   "url": "https://pds-rings.seti.org/saturn/saturn_rings_table.html",
   "credit": "Original work for this page; colours chosen to match Cassini ISS natural-colour views",
   "licence": "Own work",
   "fetched": "2026-10-11",
   "transform": "Main strip RGB: piecewise-linear ramp in radius, lit-face sRGB: D (92,86,80), C (116..122,104..110,94..99) grey-brown, inner B (190,160,124) brightening to (216,184,142) at 104,000 km and (206,176,136) at the outer edge, Cassini Division (130..134,120..123,110..112) grey, A (186..190,162..166,132..136) paler tan, Roche Division / F (170..180,165..176,158..168) grey-white. No measured radial colour scan was used. Faint strip (ring-faint-1k.png, 1024 x 4, radius 140,420..483,000 km linear, 334.6 km per texel): the alpha is DISPLAY opacity, not physical optical depth (true values are 1e-5 to 1e-7): Janus/Epimetheus ring 0.05 (149,000..154,000), G ring 0.045 plus an arc peak 0.10 near 167,500, Methone and Anthe arcs about 0.04 (Gaussian sigma 500 km), Pallene ring 0.018 (211,000..213,500) added to the E ring, E ring peak 0.14 at 237,950 km (Gaussian sigma 42,000 km inside, power law r^-3.2 outside), total clipped to 0.14. Colour: E ring pale blue-white (172,190,222) because small ice grains scatter blue, G ring neutral grey, Janus/Epimetheus warm grey.",
   "used": [
    "assets/tex/ring-main-2k.png",
    "assets/tex/ring-main-8k.png",
    "assets/tex/ring-faint-1k.png"
   ]
  }
 ],
 "strips": {
  "assets/tex/ring-main-2k.png": {
   "width": 2048,
   "height": 4,
   "radiusInKm": 66900,
   "radiusOutKm": 140420,
   "kmPerTexel": 35.9,
   "mapping": "r = 66900 + (x / W) * 73520, x in 0..W, linear",
   "encoding": "RGBA, RGB = lit-face colour (sRGB), A = sqrt(min(tau, 5) / 5), tau = 5 * A^2"
  },
  "assets/tex/ring-main-8k.png": {
   "width": 8192,
   "height": 4,
   "radiusInKm": 66900,
   "radiusOutKm": 140420,
   "kmPerTexel": 8.975,
   "mapping": "r = 66900 + (x / W) * 73520, x in 0..W, linear",
   "encoding": "RGBA, RGB = lit-face colour (sRGB), A = sqrt(min(tau, 5) / 5), tau = 5 * A^2"
  },
  "assets/tex/ring-faint-1k.png": {
   "width": 1024,
   "height": 4,
   "radiusInKm": 140420,
   "radiusOutKm": 483000,
   "kmPerTexel": 334.6,
   "mapping": "r = 140420 + (x / W) * 342580, x in 0..W, linear",
   "encoding": "RGBA, RGB = colour, A = display opacity (artistic, max 0.14, not physical)"
  }
 }
}