Why do Chollian and Koreasat never move? Geostationary satellites explained
Some satellites hang over the same spot all day. How the geostationary orbit works, what Korea uses it for, and where to look for these satellites in the sky.
One orbit a day
35,786 km above the equator, a satellite takes exactly one day to go around Earth, the same time Earth takes to turn. Moving in the same direction, it stays above one point on the equator. Seen from the ground it does not move at all.
What Korea uses it for
- Chollian (GEO-KOMPSAT) weather and ocean satellites image East Asia every few minutes; these are the satellite pictures on weather forecasts.
- Koreasat (Mugunghwa) satellites relay TV broadcasts and communications, which is why a satellite dish points to one fixed spot.
Where they are in the sky
Because they sit over the equator, from Korea they are in the southern sky, about 45° up from Seoul. They are too far away and too faint to see with the naked eye, but you can find them on a satellite's page here: the position barely changes all day.
A crowded ring
The geostationary ring is a single circle, so positions on it are allocated internationally and neighboring satellites are kept apart. At the end of their life, satellites are pushed a few hundred kilometers higher into a "graveyard" orbit to free their slot, rather than being brought down.