What defines a geostationary orbit?

A geostationary orbit is defined by its ability to remain fixed over a particular point on the Earth's surface. This is achieved when a satellite is positioned in a circular orbit directly above the equator at an altitude of approximately 35,786 kilometers (22,236 miles). In this position, the satellite's orbital period matches the Earth's rotation period; therefore, it synchronizes with the rotational speed of the Earth. This synchronization allows the satellite to effectively "hover" above the same geographical area, making it extremely valuable for applications such as telecommunications and weather monitoring.

The characteristics of a geostationary orbit specifically preclude variability in speed or altitude, ensuring a stable position relative to the Earth's surface, which is the primary defining feature. The other options describe orbits that do not maintain a constant position above the Earth and are therefore not applicable to geostationary orbits.