Heavens-Above
Heavens-Above is a free astronomy website of German origin that provides the times and paths of satellite passes, including those of the ISS, tailored to the observer's location.
Heavens-Above is a free online service that predicts when and where the ISS, the Iridium satellites, the Hubble telescope and many other objects in Earth orbit will be visible from a given location. The site was created and is maintained by Chris Peat in Germany, and for years it has been one of the basic tools of satellite watchers and amateur astronomers.
How it works
The user enters the observing location (by coordinates, city name or map), and the site calculates the visible passes from publicly available orbital data. The lists include the time, the brightness, the path across the sky, and the directions in which the object appears and disappears. The site also publishes sky charts, planet and comet data, and data on satellites entering Earth's shadow (an eclipse-like disappearance). It was also one of the best-known sources on the characteristic short, bright flashes of the Iridium satellites (Iridium flares).
Role in the UFO/UAP topic
Heavens-Above is a frequently used aid in investigating lights in the sky. A steadily moving point of light, a line of lights or a suddenly flashing object seen in the evening can in many cases be identified with it: the site shows whether the ISS, another satellite or a larger group of satellites passed over at the given time and in the given direction. This is especially important in the era of mass satellite launches (for example, Starlink trains), which are the source of many mistaken UFO reports. Skeptical researchers and organizations that investigate reports regularly refer to orbit-calculation tools of this kind.
Limitations
The site can only display known, cataloged objects with public orbital data. It does not cover classified objects or objects not listed in public catalogs, nor phenomena that are not satellites (aircraft, balloons, drones, meteors), so the fact that a sighting does not match any satellite does not, in itself, prove anything.