When a satellite follows a non-circular orbit around
the earth, the satellite's path is an ellipse with the center of the earth
at one focus. Such a satellite has variable altitude and variable orbital
speed. The point of highest altitude is called apogee. The term also applies
to the maximum distance in kilometers or miles between the satellite and
the center of the earth. (Apogee can be measured between the satellite
and the earth's surface, although this is a less precise specification
because the earth is not a perfect sphere. The difference is approximately
4,000 miles or 6,400 kilometers.) |
