A geostationary satellite is placed in a circular orbit (called the Clarke orbit) roughly 35,786 km above the equator. For the satellite to remain stationary relative to a point on the Earth's surface, its orbital period must exactly match the Earth's rotational period around its axis, which is approximately 24 hours (specifically one sidereal day). This allows ground antennas to point at a fixed location in the sky without needing complex tracking mechanisms.