Live satellite tracker

How satellite tracking works

Every tracked object in orbit, the ISS, Starlink satellites, GPS spacecraft, weather satellites, and defunct rocket bodies, is catalogued by the U.S. Space Force’s 18th Space Defense Squadron. For each object it publishes a two-line element set (TLE): two 69-character lines that describe the object’s orbit at a specific instant, called the epoch.

A TLE doesn’t store a live GPS position. Instead, a tracker feeds the TLE into a standard orbital-mechanics model called SGP4, which propagates the orbit forward from the epoch to “now” and returns a latitude, longitude, and altitude. That’s why a fresh TLE matters: the further you propagate past the epoch, the more small perturbations, atmospheric drag, the lumpy shape of Earth’s gravity, solar pressure, pull the estimate off. Within a few days, the error is usually a few kilometers; after weeks, it grows.

What you can and can’t track

Most of the ~30,000 catalogued objects are public. Amateurs with the free CelesTrak data can locate active satellites, spent stages, and debris. A subset of classified national-security payloads is withheld from the public catalog, though a community of optical observers independently tracks some of them by watching the sky.

This tool focuses on the single most-watched object in orbit, the ISS, using a free public position API so you can see orbital motion in real time without any account. For a full catalog, professional trackers layer a live TLE feed over a 3D globe.

Watching the ISS pass overhead

Because the ISS orbits at about 400 km and reflects sunlight, it’s often visible to the naked eye at dawn or dusk as a bright, fast-moving point of light, no telescope needed. NASA’s Spot the Station service will email you when a visible pass is coming for your location.

Why the position is an estimate, not a live GPS ping

Most satellites do not broadcast their location. The ISS is a partial exception because it carries GPS receivers and its position is published frequently, which is why this tracker can show a near-real-time fix. For the tens of thousands of other objects in the public catalog, the only available data is the periodic TLE, so any position you see for them is a propagated estimate whose accuracy depends on how recently the element set was updated. Professional operators refine those estimates with radar and optical observations from ground stations around the world.

That gap between “where the model says it is” and “where it actually is” matters for real work. Collision-avoidance teams need tight position accuracy to decide whether to move a satellite out of the way of debris, and small errors compound over days. It is also why space domain awareness, the military and civil effort to track everything in orbit precisely, is a growing priority as low Earth orbit fills with satellites.