📘 Definition
A Highly Elliptical Orbit (HEO) has a large difference between its perigee (closest point to Earth) and apogee (farthest point). The classic example is the Molniya orbit: ~500 km perigee, ~40,000 km apogee, 63.4° inclination, ~12 hour period. A satellite in a Molniya orbit spends most of its time near apogee over the northern hemisphere, providing quasi-stationary coverage for high-latitude regions where GEO satellites sit low on the horizon. Used by Russian early warning and communications systems.