🛰️Sky Sentinelv0.3.4spin the Earth · the orbital shells we filled, made visible←Space Pulse
Orbital shells
Object types
Building the orbital shells…
drag to rotate · scroll to zoom
🛰 Starlink Live
0 of — active
real TLE · SGP4 · updates 10s
— recent (last 14d)
objects shown:—
view altitude:—
🚀 Last 10 launches
Fetching Launch Library…
🛰️ Sky Sentinel v0.3.4
The orbital shells we filled, made visible. Now with real-time SGP4 propagation for two layers and click-to-identify on every dot.
Sky Sentinel is a rotatable 3D Earth that shows the regions of space humans have filled with hardware — working satellites, spent rocket bodies, the Starlink cloud, and the debris left from sixty years of launches and a few notable collisions. Built to teach, not to alarm. Spin the planet, toggle an orbital shell, drop the live Starlink constellation onto it, click any object to learn what it is and how it got there.
Sister tool to Space Pulse — Space Pulse tracks the launches; Sky Sentinel shows what those launches leave behind. Launches create the shells.
The three orbital shells
LEO — Low Earth Orbit (160–2,000 km). The crowded one. The ISS, Hubble, Starlink, most Earth-observation satellites, and the overwhelming majority of tracked debris. Objects here circle Earth in about 90 minutes.
MEO — Medium Earth Orbit (2,000–35,000 km). The quiet middle. Mostly navigation constellations — GPS, Galileo, GLONASS — at around 20,000 km.
GEO — Geostationary (35,786 km). The thin ring. Satellites here orbit at the same rate Earth turns, so they appear to hover over one spot — weather and communications satellites.
What's in v0.3.4 (real, not representative)
Rotatable 3D Earth (Three.js), drag to rotate, scroll to zoom — same as v0.1
Starlink Live — toggle in the top bar pulls real TLE from the CelesTrak starlink group, samples ~750 of them (the overlay shows the live total), propagates true positions via SGP4 every 10 seconds, renders as an orange Points cloud. Toggle on and the LEO/MEO/GEO shells auto-hide so you see only Starlink.
Starlink "last 14 days" overlay — three-state cycle inside the Starlink Live overlay: off / overlay / only. Filters by TLE epoch to show just the recently-launched batches that haven't dispersed yet — these render as the bright yellow chains, the "Starlink trains" visible in the sky after a launch.
Load Live Debris from CelesTrak — button in the right panel pulls the last-30-days group, parses TLE, propagates each via SGP4, renders as a green Points cloud alongside the curated set. Click again to clear.
Click any dot — curated or live — to identify it. Curated objects show their pre-written story. Live objects show name (e.g. STARLINK-30123), NORAD ID, computed altitude/inclination/orbital period, and the SGP4 derivation source. (One soft edge: clicks on the yellow recent-overlay show a generic "Starlink (recent batch)" label — per-satellite naming for that overlay is still a follow-up.)
Curated teaching dataset (the ISS, Hubble, GPS, GEO weather sats, plus representative fragments from the 2007 Fengyun-1C ASAT test and the 2009 Cosmos 2251 / Iridium 33 collision) — still baked in, still clickable, still the entry point if you've never opened a sat-tracking tool before.
Toggle orbital shells and object types to isolate what you want to study.
NOAA Space Weather Prediction Center feed — current geomagnetic K-index from SWPC. Dual-endpoint fallback + retry button if NOAA throttles.
Top-bar suite navigation — full SnapBasin LLC sister-tools strip (SnapBasin · Watershed Pulse · Quake Sim · Space Pulse · Sky Sentinel · Quantum Pulse) + OPA cross-link.
What's still NOT in v0.3.4 (honest)
The full 25,000+ object catalog rendered at once. Even SGP4 propagation of every tracked object every animation frame would freeze a phone. We render samples (~750 Starlink, ~400 recent CelesTrak debris) and say so. This is a deliberate honesty choice, not a limitation hidden.
Conjunction / collision prediction. Computing close-approach risk between objects is real engineering — slated for v0.4, not faked here.
Per-satellite naming on the yellow recent-overlay. Clicks identify it as "recent batch" rather than the specific Starlink. Parallel-array tracking patch is still to come.
Gamma-ray bursts. Deliberately deferred. GRBs happen on the deep-sky celestial sphere — a different coordinate system — so they belong in a future "look outward" mode, not bolted onto an Earth-centered tool.
How rate-limiting works (important context)
All the live data — Starlink TLE, debris TLE, space weather — comes from public federal/academic APIs (CelesTrak, NOAA SWPC) that throttle by IP address. If you see a friendly "rate-limited (HTTP 429)" or "retry" message, it means your browser hit the per-IP cap. Wait 5–15 minutes and the API lets you back in. Other visitors to this site from other IPs will still be working normally — there's no shared backend, so there's no shared rate limit.
Data sources
CelesTrak — orbital element catalog (celestrak.org). Two groups in use: starlink (live constellation) and last-30-days (recent launches/debris).
satellite.js v5 — SGP4 propagator, the model two-line element sets (TLEs) are generated for (Hoots & Roehrich, Spacetrack Report No. 3, 1980; Vallado et al., Revisiting Spacetrack Report #3, AIAA 2006-6753).
NOAA Space Weather Prediction Center — Kp index (services.swpc.noaa.gov), dual-endpoint fallback.
Curated teaching dataset — compiled from public catalog data; famous-event fragments are representative scatter, not the literal tracked pieces.
The Space Devs Launch Library 2 — recent launches and pad coordinates (ll.thespacedevs.com).
Natural Earth — 1:110m coastlines (public domain, via the martynafford/natural-earth-geojson mirror).
Earth texture — procedurally shaded in-browser (no external image dependency).
Version history (short)
v0.3.4 (2026-10-14) — Launch list and place search now center the globe on the right spot (the spin angle had a sign error that could park the pad on the far side of the Earth) · version labels unified · Starlink total read from the live feed instead of typed in · SGP4 credit sourced · Launch Library and Natural Earth added to Data sources.
v0.3.3 (2026-05-25) — Starlink Live SGP4 cloud + 14-day overlay · Load-live debris promoted from representative to real SGP4 · Points-cloud click identification · Space Weather dual-endpoint + retry · header rework w/ full sister-tools strip · graceful 429/403 messaging across all fetches.
Built by Travis Jenkins / User Zero 🦄 · SnapBasin LLC · February 2026 → October 2026
Static HTML. No backend. No tracking. No user data stored. Educational/observational use.
Not affiliated with NASA, NOAA, CelesTrak, SpaceX, or any space agency. The debris problem shown
here is real, but the tone is deliberately instrument-calm: this is a tool for understanding,
not a scare.
A note from the builder
Single developer. About to be a 49‑year‑old father of four — three teenagers at home.
If you see something wrong, please let me know — I’ll change it as soon as I can. I’ll credit you if you want the credit.
Some labs are better than others; a few have obvious broken bits I’m still working through. Some were built early, some late — they don’t all look the same, but they share a feel.