What is the term for the highest point of an orbit?

The term for the highest point of an orbit is "apogee." In celestial mechanics, apogee refers specifically to the point in the orbit of an object (like a satellite or moon) where it is farthest from the Earth. This concept is crucial for understanding orbital dynamics and the behavior of objects in space.

In contrast, the term "perigee" describes the point in an object's orbit where it is closest to Earth. "Zenith" generally refers to the point in the sky directly above an observer, rather than being used in the context of orbits. Similarly, "apex" is a more general term that can refer to the highest point of an object or figure, but it does not specifically denote a point in the context of orbits. Thus, "apogee" is the appropriate term for the highest point of an orbit, making it the correct answer.