Geostationary orbit corresponds to which altitude?

• A. 160 to 2000 km
• B. 2000 to 35785 km
• C. 0 to 5000 km
• D. 35786 km

Answer: (D)

Geostationary orbit is defined by the satellite’s orbital period matching Earth's rotation, which is one sidereal day (about 23 hours 56 minutes). For a circular orbit, this fixed period requires a specific orbital radius set by orbital dynamics. That radius is about 42,164 kilometers from the center of the Earth; subtracting Earth's average radius (~6,371 km) gives an altitude of roughly 35,786 kilometers above the surface. At this altitude, the satellite’s orbital speed and the planet’s rotation align so the satellite stays fixed above the same point on the equator, which is why GEO is used for many communications satellites. Other altitude ranges would produce different orbital periods and would not keep the satellite stationary relative to the Earth.