The orbit eccentricity "indicates the deviation of the orbit from a perfect circle. A circular orbit has an eccentricity of 0, while a highly eccentric orbit is closer to (but always less than) 1. A satellite in an eccentric orbit moves around one of the ellipse’s focal points, not the center." (National Aeronautics and Space Administration, 2009)
"Catalog of Earth Satellite Orbits". Earth Observatory, National Aeronautics and Space Administration. Last modified September 4, 2009.
Accessed February 1, 2019.