About
About this site
spacetrack.eu is an independent, one-person project that shows where the crewed space stations are right now. It has been online in one form or another since 2001.
How it works
The chain is deliberately simple and has no third-party tracking in the pipeline:
- Orbital data. CelesTrak publishes two-line element sets (TLEs) for every tracked object, including the ISS (NORAD 25544) and Tiangong (NORAD 48274).
- Propagation. The TLE is propagated with SGP4 to get the current sub-satellite point, altitude and velocity vector.
- Rendering. xplanet 1.3.1 renders an orthographic view of Earth from directly above that point, including the day/night terminator and cloud layer.
- Delivery. The frame is written to disk on a small server and served as a normal image. The page polls for a new frame at a fixed interval.
Nothing about that is magic, and nothing about it needs a database or a login. It is a cron job, an orbital propagator and an old piece of rendering software — which is also why the site stays fast and does not ask you to accept a dozen scripts.
Accuracy
Positions are accurate to within a few kilometres, which is far better than needed for "look west in two minutes". Accuracy degrades slowly between TLE updates because atmospheric drag changes the orbit continuously; the data is refreshed regularly to correct for that.
Advertising
The site is free and has no subscription. Hosting, bandwidth and the time to maintain it are paid for by display advertising. Ads are served by Google AdSense and are clearly separated from the content. There is no paywall and no account to create.
Contact
Questions, corrections or permission requests: see cweb.nl for contact details. Corrections to orbital facts are genuinely welcome — if a number on this site is wrong, it should be fixed.
Operator: Jeroen Wouda · CWEB.NL · the Netherlands. See also privacy policy and terms of use.