FAQ

No. The Orbit Visualizer runs entirely in your browser and is free to use with no account or download required. Adding orbits, running ground tracks and access passes, planning maneuvers, screening conjunctions, downloading CSV exports, saving scenarios locally, and copying share links are all available without signing up. Cloud saves and a few power features (longer analysis spans, more ground sites and nodes, full constellation groups, OEM/CZML export) are part of ExoAtlas Pro. See the Plans & limits page for the full comparison.

Use SGP4 for real satellites with TLEs — it is the model TLEs are fitted for, including atmospheric drag and the SDP4 deep-space branch for high orbits. SGP4 is the default for TLE input and is the right choice for pass prediction, conjunction screening, and ground tracks. Use J2 secular when you want to show orbital-plane precession (nodal regression, sun-synchronous design) with classical elements or a state vector. Use two-body for teaching orbit geometry or quick sketches where perturbations do not matter. See the full guide: Propagation models.

The Orbit Visualizer’s SGP4/SDP4 port matches the published Vallado verification set (“Revisiting Spacetrack Report #3”, AIAA 2006-6753) to far below the 0.1 m acceptance tolerance across all 33 verification runs (666 states). The practical accuracy limit is TLE age: SGP4 is roughly 1–3 km from truth at a fresh TLE’s epoch, and the error grows as the element set ages. Refresh your TLEs before time-sensitive predictions. Full methodology and case tables: validation page.

This warning appears when you propagate a TLE object with two-body or J2 instead of SGP4. TLE elements are mean elements fitted by the SGP4 process; treating them as osculating (instantaneous) elements causes the predicted position to diverge from reality by hundreds of kilometers within a day. Use SGP4 for any orbit defined by a TLE. See How to read a TLE for the mean-vs-osculating distinction.

The 3D scene uses J2000 (EME2000). SGP4 states are computed in TEME — the native SGP4 output frame — and converted to J2000 through the documented IAU-76 precession and a truncated IAU-1980 nutation (the 6 largest terms). Earth-fixed products such as ground tracks and access passes use TEME rotated to ECEF by GMST, the standard approximation for TLE work. All times are UTC. CSV and OEM exports label the frame as EME2000.

Yes. The ExoAtlas TLE Parser has a Visualize in 3D button that passes the TLE directly to the Orbit Visualizer — the orbit opens automatically in the browser with SGP4 selected.

The stale badge appears when a TLE’s epoch is more than 7 days old. SGP4 accuracy degrades as element sets age, so a stale entry may produce position errors significantly larger than the 1–3 km near-epoch baseline. The catalog is refreshed daily from Space-Track, so entries are usually current. See TLE epoch age for details.

SGP4 requires TLE mean elements as input and cannot ingest a post-burn osculating state. When you add a maneuver to an SGP4 object, the app automatically switches the post-burn arc to J2 secular propagation — the most physically honest choice available without a full numerical propagator. The object card labels the post-burn arc accordingly.

If a maneuver burns a satellite onto a hyperbolic escape trajectory (eccentricity ≥ 1), the visualizer cannot continue rendering the path. The maneuver is still recorded and the ΔV budget is shown; the post-burn arc display is suppressed with this note.

CSV ephemeris (time-stamped J2000 position and velocity with header comments; free up to 24 hours), CCSDS OEM 2.0 (Pro), CZML (Pro), and PNG captures of the 3D view and the ground-track map (always free). See Plans & limits for details.

Copy Link encodes every scenario object — name, propagator, orbital elements or TLE lines, color, and maneuver nodes — plus your ground sites into a compact base64 URL (?s=). Opening the link in any browser rebuilds the exact scenario. The link is limited to roughly 1,900 characters; very large scenarios show “Scenario too large for a link — use Save instead.” Sharing is always free. Full guide: URL API.

Local save stores named scenarios in your browser’s localStorage — always free, always private, no account required, but tied to that browser and device. Cloud save (ExoAtlas Pro) stores scenarios server-side so you can reload them on any device. Pro users get up to 50 cloud slots with a 100 KB body limit each. See cloud scenario detail.