Which statement is most accurate?

• A. A geosynchronous orbit is a specific type of geostationary orbit.
• B. A Molniya orbit is a specific type of geostationary orbit.
• C. A highly-elliptical orbit is a specific type of polar orbit.
• D. A geostationary orbit is a specific type of geosynchronous orbit.

Answer: (A)

Geosynchronous refers to any satellite that has the same orbital period as Earth’s rotation, about 24 hours. A geostationary orbit is the special case where, in addition to the 24-hour period, the satellite stays in the equatorial plane and follows a circular path, so it appears fixed over the same point on Earth. Because of that fixed position, geostationary is a specific type of geosynchronous orbit.

Molniya orbits, being highly inclined and highly elliptical, do not stay over one point on Earth and thus are not geostationary. A highly elliptical orbit isn’t necessarily polar; eccentricity describes shape while inclination describes tilt, so such an orbit can have many inclinations, not just polar. A geosynchronous orbit, by definition, is not restricted to geostationary behavior and can have various inclinations and eccentricities, whereas geostationary is the narrow, fixed-ground-position subset.

So the correct way to understand the relationship is that a geostationary orbit is a specific type of geosynchronous orbit.