LowEarth

Methodology

Catalog refresh

Every 3 hours, a Vercel Cron job pulls 21 small CelesTrak groups in parallel (stations, science, Starlink, OneWeb, Iridium-NEXT, GPS/GLONASS/Galileo/BeiDou, GEO, weather, NOAA, GOES, Intelsat, SES, visual, last-30-days, plus the four major debris clouds: Cosmos 1408, Fengyun-1C, Iridium-33, Cosmos-2251). We dedupe by NORAD ID and snapshot the orbital elements into our archive for delta detection.

The per-purpose groups are curated by mission type, which gives better category accuracy but leaves out anything that fits no theme — old calibration spheres, geodetic targets, early comsats. A final active catch-all closes that gap while the topical groups keep first claim on categories.

CelesTrak answers a repeat request inside its refresh window with an HTTP 403 whose body reads “GP data has not updated since your last successful download”. That is a conditional-GET “not modified”, not a rejection, and we treat it as one: element sets refresh every 2 hours while our cron runs every 3, so some overlap is expected and healthy.

Orbit classification

We classify by orbital elements (semi-major axis, eccentricity, inclination) rather than instantaneous altitude. Naively classifying by current altitude misclassifies Molniya satellites as LEO when they happen to be near perigee.

Position propagation

Positions are computed using SGP4 — the standard analytical propagator used with TLE data. We do this in your browser via satellite.js, so the position you see is always computed for “now,” using the most recent TLE we ingested. We never claim “real-time” — positions are propagated from TLEs that may be hours old.

Per-object pages

Each page combines our proprietary computed layers (live orbit, decay forecast, pass predictions, constellation graph) with attributed enrichment from Wikipedia (CC-BY-SA, isolated in attribution boxes), Wikidata (CC0), Wikimedia Commons (per-file licenses), TheSpaceDevs Launch Library 2, and the NASA NSSDCA Master Catalog. Wikipedia text is always rendered in a clearly labeled box to avoid ShareAlike contaminating the rest of the page.

Visibility predictions

Pass predictions use SGP4 propagation against your observer location (latitude, longitude, altitude). We compute look angles (azimuth, elevation) and report passes above 10° peak elevation.

Data sources and citation

Element sets come from CelesTrak (Dr. T.S. Kelso) (open · attribution requested).

The globe's base map is NASA Blue Marble Next Generation, and its optional Clouds layer is live VIIRS/SNPP corrected-reflectance imagery. Both are obtained through NASA GIBS. We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Science Data and Information System (ESDIS).

Cloud imagery is fetched server-side and cached, never from your browser. The daily composite is built from orbital swaths, and a polar orbiter images each longitude once a day at a fixed local time — so we composite the two most recent days, using the freshest available pixel everywhere rather than showing a third of the planet as cloudless because its overpass has not happened yet.

Where we sit in the tracking landscape

LowEarth is a public, consumer-facing window onto the orbital catalog — built for curiosity, education, and journalism, not for operations. We use open data (CelesTrak's public element sets) and never claim the precision of a sensor network. For operational tracking, conjunction screening, and threat assessment, the authoritative sources are Space-Track.org (the US Space Force's public catalog), CelesTrak (element sets and analysis), and commercial space-domain-awareness providers such as LeoLabs, which operates its own global radar network and produces higher-precision data for satellite operators and governments. We see ourselves as the front door to that world — the place a curious reader starts before reaching for professional tools.