ISS (ZARYA) — Visible Passes (NORAD 25544)

Find out when ISS (ZARYA) is visible to the naked eye from your location. Share your position on this page and WatchSat computes the next passes in your browser: the exact rise time, which direction it appears and disappears, how high it climbs, and how long it stays in view. It orbits at roughly 423–430 km with a 93-minute period, inclined 51.6° to the equator.

A pass is visible when the satellite is above your horizon while your sky is dark and the spacecraft is still lit by the Sun — which is why sightings cluster around dawn and dusk. Predictions use the SGP4 orbital model with the CelesTrak element set currently loaded for this satellite — see its exact epoch on the live tracking page below.

What counts as a visible pass

Three conditions have to hold at the same moment, and WatchSat tests all three rather than just the first. The satellite must be above your horizon — passes peaking below 10° are dropped, because that low it is behind rooftops, trees and haze. Your sky must be dark: the Sun has to be more than 6° below your horizon, the end of civil twilight. And the satellite itself must still be in sunlight, which is tested against Earth’s shadow — that is why it can fade out mid-sky, and why sightings cluster around dawn and dusk. A pass that survives all three is then checked against a brightness estimate and dropped if it is fainter than magnitude 6, the naked-eye limit under a dark sky.

How the prediction is computed

Everything happens on your device. Your position and the current element set go into SGP4, which is stepped over the next five days to find each horizon crossing, then refined around the peak to pin the maximum elevation and its time; the search re-runs every few minutes so countdowns stay honest. Nothing about your location is sent anywhere. Accuracy follows the age of the element set — fresh data puts a pass within seconds of its real time, a stale fit can be minutes out, and a satellite that manoeuvres invalidates the fit entirely.

Track ISS (ZARYA) live in 3D · How to spot a satellite with the naked eye · Tonight’s aurora forecast

Other satellites with pass predictions

This station is catalogued in pieces: ISS (UNITY) passes · ISS (ZVEZDA) passes · ISS (DESTINY) passes · ISS (NAUKA) passes. Each module is tracked as its own object, but they fly as one vehicle, so those pages show the same passes as this one.

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