Why must a geostationary satellite orbit over the equator?

A geostationary satellite is placed in a specific orbit around the Earth in order to stay synchronized with a particular point on the Earth's surface. This allows the satellite to appear stationary from the perspective of an observer on the ground. To achieve this stationary position, the satellite must be located directly above the equator.

The reason for this requirement is primarily due to the rotation of the Earth. The Earth completes one full rotation on its axis every 24 hours, causing a day-night cycle. To maintain a stationary position relative to the Earth's surface, a geostationary satellite must have an orbital period equal to the Earth's rotation period.

The satellite achieves this by orbiting at an altitude of approximately 35,786 kilometers (22,236 miles) above the Earth's equator. At this specific altitude, the satellite takes exactly 24 hours to complete one orbit, matching the Earth's rotational period. As a result, the satellite remains fixed above a specific point on the equator, providing continuous coverage to the same geographical area on the ground.

If a geostationary satellite were placed in an orbit that is not directly above the equator, it would not stay synchronized with a fixed point on the Earth's surface. As the Earth rotates while the satellite orbits, the satellite's position would appear to shift relative to the observer on the ground. This would result in a loss of continuous coverage and defeat the purpose of having a geostationary satellite in the first place.

If it isn't over the equator is must obviously wander above and below the equator, since the center of its orbit is the center of the earth. The orbit is inclined to the equatorial plane.

If the satellite keeps going from north to south and back again, it isn't geostationary. DirecTV would not work, for example.

Geostationary orbit is the distance from the earth's equator that falls in sync with the planet's rotation. That specific distance (35,700km above equator) stays on a fixed point in orbit.