Top 3 Satellite Pass Predictors Compared

A satellite’s position is fully determined by two lines of numbers and a propagation model. Feed a current TLE through SGP4, add your latitude and longitude, and you get the time, duration, and maximum elevation of its next pass over your head.

Getting that answer is oddly awkward in practice. The convenient tools maintain their own satellite catalogues, which is excellent for the ISS and the popular amateur radio satellites and unhelpful the moment you have a TLE for something not on their list — a newly launched CubeSat, an object from a fresh catalogue update, or a historical element set you want to reproduce a pass from. At that point you need a tool that accepts your two lines, not one that offers you a dropdown.

How to judge a pass predictor

Can you paste your own TLE? Catalogue-driven tools and TLE-driven tools solve different problems.

Does it report elevation? A pass that peaks at eight degrees is behind the neighbour’s roof. Maximum elevation decides whether a pass is worth setting an alarm for.

Does it distinguish visible from merely overhead? Optical visibility needs the satellite sunlit and your sky dark. Radio contact does not care.

How fresh must the TLE be? Element sets decay in accuracy within days, which is the single largest error source in any prediction.

The comparison

Facts checked August 2026; plans can change.

CelesTrak

CelesTrak is where the TLEs come from. It provides free element sets for most public satellites, updated multiple times daily, and it is the reference the rest of this ecosystem depends on — including any tool you use to do the propagation.

It is a data resource maintained for people who know what they are doing with it. If you want a friendly “when can I see it” answer, this is the input to that question rather than the answer.

ESA Orbital Prediction and Overpass Tool

ESA’s OPOT generates and visualises satellite overpasses from an agency-run service, which brings institutional credibility and a visualisation you can actually reason about rather than a bare list of times.

It is built in the context of Earth observation data, so the framing and the satellite selection lean that way. For planning an evening’s naked-eye observing it is more apparatus than the question needs.

Ham Sat Tracker

Ham Sat Tracker is purpose-built for amateur radio operators predicting when a satellite will be workable. That focus produces exactly the right output for that use: passes, elevations, and timings for the satellites hams actually use.

If your object is not an amateur satellite, the specialisation stops helping.

Satellite Pass Predictor (Manual TLE)

Ours is the one that takes your two lines. Paste a satellite’s TLE and your location, and it predicts the next visible pass with timing, duration, and maximum elevation. No catalogue, no dropdown, no assumption about which objects are interesting — whatever TLE you have, it will propagate. It runs entirely in your browser.

Two limitations, and the first is genuinely important. It does not fetch TLEs, so you must supply a current one — and because element sets degrade over days, a stale TLE will produce a confidently wrong prediction. Get yours from CelesTrak immediately before predicting. Second, it handles one satellite at a time from data you paste, so it is not a tracking dashboard and will not watch a constellation for you.

Which one to pick

• If you need current element sets, get them from CelesTrak.
• If you want an agency-grade overpass visualisation, use ESA’s OPOT.
• If you are planning amateur radio contacts, use Ham Sat Tracker.
• If you have a TLE in hand for any object at all and want its next pass, use ours.

How to do it with Satellite Pass Predictor (Manual TLE)

1. Fetch a current TLE for your satellite from a source such as CelesTrak.
2. Open the Satellite Pass Predictor (Manual TLE) and paste both lines along with your location.
3. Read the pass time, duration, and maximum elevation, and discount anything peaking below about twenty degrees unless your horizon is unusually clear. More astronomy tools are in the tools directory.

You might also need

• Telescope Magnification Calculator — if you intend to follow the pass optically.
• Moon Phase Calculator — because a bright moon decides what is visible at all.

Frequently asked questions

Is there a free satellite pass predictor that doesn’t need an account?

Yes — CelesTrak’s data, ESA’s OPOT, and Ham Sat Tracker are all free to access. Ours needs no account because the site has no signup at all.

How long is a TLE accurate for?

Accuracy degrades within days, and faster for objects in low orbits where atmospheric drag is significant. For a pass tonight, use an element set published within the last day or two. CelesTrak’s documentation on TLE accuracy explains the propagation model’s assumptions and limits.

Why can’t I see a satellite that is overhead?

Optical visibility requires the satellite to be lit by the Sun while your own sky is dark — which is why passes cluster in the hours after dusk and before dawn. At local midnight most low satellites are in Earth’s shadow and invisible regardless of elevation.

Final thought

Refresh the TLE before every prediction. Everything else in the calculation is deterministic; the element set is the part that goes stale.

Try the free Satellite Pass Predictor (Manual TLE)