Skyfold Satellite Pass Predictor

What it is for

This tool predicts the passes of satellites over a place: when a satellite rises above a minimum elevation, when it is highest and when it sets, with compass directions. It also tells you which passes you can actually see with the naked eye — the satellite must be lit by the Sun while your sky is dark.

Predictions use SGP4/SDP4, the standard model for the two-line element sets (TLEs) published for every tracked object. Skyfold's own implementation reproduces the official verification ephemerides of Vallado and colleagues to well under a metre. You can paste elements or let the tool fetch them from CelesTrak; each CelesTrak query is cached for two hours, as CelesTrak asks.

Worked example

The second example uses Madrid (40.4168, -3.7038, Europe/Madrid), starting 2026-11-08 at 00:00 for three days, minimum elevation 15°, with the ISS elements of 7 November 2026. The summary reads 13 passes above 15° in 3 days from 2026-11-08 00:00; 2 are visible to the naked eye.

Most rows say in Earth's shadow: in early November the ISS crosses Madrid's night sky while it is itself in darkness. The two exceptions are evening passes. On 2026-11-10 the ISS rises at 19:18 in the south, peaks at 21.3° in the south-east at 19:20 and sets at 19:22 in the east; it is visible from 19:18 to 19:20 for 107 s. On 2026-11-09 a higher pass (36.7°) is visible for only 11 s right after rising at 20:05 before the ISS slips into the Earth's shadow.

The element table shows the ISS epoch 2026-11-07T04:59:17Z, an age of 0.75 days, a period of 92.96 minutes and an inclination of 51.632°.

How to read the result

• Rise, Highest and Set give local times with a 16-point compass direction; Max elevation is the highest point above the horizon (90° is overhead).
• Duration counts the seconds above your minimum elevation.
• Condition is visible, in daylight (your sky is too bright, the Sun is higher than 6° below the horizon) or in Earth's shadow (the satellite is dark).
• Visible from–to gives the naked-eye window and its length. A window is listed only when it lasts at least 10 seconds.
• Age (days) warns you about stale elements; the tool adds a warning above three days.

Tips and common mistakes

• Fetch fresh elements before an observing session: after a week, times can be off by minutes, and ISS reboosts shift them suddenly.
• Use a minimum elevation of 10° to 20° where trees or buildings block the horizon.
• Passes listed as in Earth's shadow still happen; radio amateurs can use them.
• The time zone sets the local times in the table; the API result also carries UTC times.
• Paste several satellites at once — the name line above each set is used in the table.

FAQ

Where do the elements come from?

From any source you paste, or from CelesTrak by NORAD catalogue number (up to five per request) or by group such as space stations or the brightest satellites.

How bright will the satellite be?

The tool does not predict magnitudes. The ISS is usually one of the brightest objects in the sky during a visible pass.

Why is a high pass not visible?

Because the satellite is in the Earth's shadow. Around midnight in winter, low-orbit satellites are often dark even when overhead.

Can it predict geostationary satellites?

No. Objects that do not rise and set — with periods above about 21 hours — produce no passes.