What is the approximate altitude of a geostationary orbit?

What is the approximate altitude of a geostationary orbit?

• A. 20000 km
• B. 35786 km
• C. 600 km
• D. 10000 km

Answer: (B)

Geostationary orbits require the satellite to complete one full orbit in the same time that Earth rotates, about 23 hours 56 minutes. That condition fixes the orbital radius at roughly 42,164 km from Earth's center. Subtract Earth's average radius (~6,378 km) to get the altitude above the surface, which comes out to about 35,786 km. This is why geostationary satellites stay fixed over a point on the equator. The other numbers are typical for different kinds of orbits (lower altitudes for low Earth orbits, and higher numbers than needed for a 24-hour period), so 35,786 km is the correct approximate altitude.