About this site

What this is

Give the tracker an observer location and it works out when satellites will be above your horizon: rise and set times, peak elevation, compass bearings, and a polar plot of the path across your sky. A world map shows current positions with a heading arrow and roughly an hour of ground track either side of now.

It is free, needs no account, and is aimed at anyone who wants to know when something will pass overhead — satellite spotters, amateur radio operators, students, Earth-observation users checking an acquisition, and people who just want to see the Space Station go by.

Who runs it

This is an independent, non-commercial project built and maintained by one software engineer. It is not a company, a product, or a startup. It is operated from the United States.

There is nothing to buy and nothing to sign up for. The site carries no advertising, no sponsored content, no affiliate links, and no analytics or tracking scripts of any kind.

It is not affiliated with or endorsed by NASA, ESA, EUMETSAT, Celestrak, or any government or space agency. It uses their published data under their own public terms, and credits each source below.

How it works, technically

The app is a static web page with no backend. When you load it, your browser downloads the HTML, CSS and JavaScript, and from then on every calculation — orbit propagation, look angles, pass geometry, the map — happens locally on your own machine.

Orbits are propagated with SGP4, the standard model for two-line element sets, via the open-source satellite.js library. Country and state outlines on the map come from Natural Earth data bundled with the site.

There is no application server, no database of users, and no login for the site itself. The only server-side code in the entire project is two small Cloudflare Pages Functions: one that redirects the hosting provider's default address to this domain, and one that receives messages from the feedback form. Neither is involved in tracking satellites.

Because everything is local, the tracker also works offline. A service worker caches the app so it keeps running without a connection, using the most recent orbital data your browser already downloaded.

You can verify all of this yourself. The site is plain client-side JavaScript — open your browser's developer tools and read the source, or watch the network tab and see exactly which requests are made.

Where the data comes from

• Two-line element sets (TLEs) — from Celestrak, a long-standing public source for orbital elements. These are fetched directly by your browser and cached locally for a day.
• Precise Sentinel orbits — optionally from the ESA Copernicus Data Space Ecosystem, which publishes determined orbit files far more accurate than a TLE. This requires a free ESA account, and is explained in the next section.
• Map outlines — Natural Earth, public domain.
• Libraries — satellite.js for SGP4 and JSZip for reading compressed orbit files, both loaded from a public CDN.

About the optional Copernicus sign-in

One feature asks for a username and password, so it deserves a plain explanation.

ESA publishes precise orbit files for the Sentinel satellites, accurate to centimetres rather than the kilometres a TLE gives you. Downloading them requires a free account with ESA's Copernicus Data Space Ecosystem. If you want that precision, the tracker offers a sign-in box. It is entirely optional — every other feature works without it, and most people never touch it.

What happens to what you type:

• Your password is sent directly from your browser to ESA's own authentication endpoint at identity.dataspace.copernicus.eu, over HTTPS.
• It is never sent to sat-above.com. That is not a policy promise — this site has no server that could receive it. There is nowhere for it to go.
• Your password is never stored, not on any server and not in your browser.
• What is kept locally, in your own browser's storage, is your username and the access tokens ESA issues back, so you are not asked to sign in repeatedly. Clearing your browser's site data for this domain removes them.

These are credentials for ESA's service, used against ESA's own servers. If you would rather not enter them here at all, that is a reasonable choice: skip the feature and the tracker works normally on public TLE data.

Accuracy and limits

Pass predictions are only as good as the orbital data behind them. TLEs are updated regularly but drift, so predictions degrade the older the element set is and the further into the future you look. Expect good results for the next few days and progressively looser ones after that.

SGP4 is an analytical model with known approximations. Atmospheric drag varies with solar activity, satellites manoeuvre without notice, and newly launched objects take time to be catalogued accurately.

This site is for observation and general interest. It is not suitable for operational, navigational, or safety-critical use, and comes with no warranty of any kind.

Privacy

No accounts, no cookies set by this site, no advertising or analytics scripts, and nothing about your observer location ever leaves your browser. The privacy page sets out exactly what is and is not collected, including the small amount of information stored when you use the feedback form.

Contact

Questions, bug reports, a satellite you think belongs in the default list, or security and site-categorisation enquiries:

[email protected]

There is also a feedback form on the tracker itself, under Feedback in the top bar, if you would rather not use email.

This is a one-person project, so replies are best-effort and may take a while. Bug reports are most useful with your browser, the satellite involved, and what you expected to happen.

Go to the tracker