Molniya orbit

Meanings

1. A highly elliptical orbit with an eccentricity of 0.74, inclination of 63.4 degrees, an argument of perigee of −90 degrees, and an orbital period of half a sidereal day, around the Earth.
2. By analogy, the equivalent orbit for the southern hemisphere, with the argument of perigee changed to +90 degrees.
3. Both the northern and southern hemisphere orbits for the Earth.
4. By analogy, equivalent orbits for other bodies, which provide low apparent motion across the dome of the sky at apoapsis, allowing long duration communications/observation with low tracking rates at polar latitudes.
5. The orbits around Earth and other bodies with these qualities.

Etymology

From Russian мо́лния (mólnija, “lightning”) + orbit. The Russian word was used as the name for a series of Soviet/Russian communications satellites, and the orbits which they were placed in.