The High Altitude Satellite Observers
Home Page

An Atlas Centaur rocket travels the lonely region between 600km & 36000km altitude in a Geosynchronous Transfer Orbit (GTO). Centaur rockets are probably some of the easiest high altitude satellites to observe, since many flash brightly. Source: Composition of NASA images

What are High Altitude Satellites?

The exact definition of a high altitude satellite orbit varies. USSPACECOM considers any object with an orbital period greater than 225 minutes (approx. 5900km altitude for a circular orbit) to be "high altitude", since solar & lunar gravitational forces become significant perturbing effects on the satellite orbit. However, on this web site I use a more broad definition of any satellite beyond LEO. Hence I have considered any satellite that spends an appreciable part of its orbit beyond 1500km to be "high altitude", since there are few satellites beyond this altitude until we reach the medium earth orbits of GPS & Glonass satellites & those in geosynchronous orbit.

This web site provides specialised information for observers of high altitude satellites including tips on observing & observing lists for different classes of high altitude satellites. If you are new to satellite observing other web sites, most notably the Visual Satellite observers home page (US web site), provide general information which you may find interesting.