A highly elliptical orbit (HEO) has a low perigee and a very high apogee. Near apogee the satellite moves slowly and stays over the same area for hours. With an inclination of 63.4° the apogee stays in the same place in the orbit.
| Orbit | Period | Characteristic | Use |
|---|---|---|---|
| Molniya | ± 12 hours | Apogee ± 40,000 km over the northern hemisphere; ± 8 hours usable per orbit | Soviet and Russian communications and warning |
| Tundra | ± 24 hours | Returns over the same area at the same time every day | Russian missile warning system EKS (Kupol) |
Russia uses these orbits because GEO satellites above the equator see its northern regions poorly. The United States uses HEO for infrared missile warning sensors over the polar regions, among other things.