Highly elliptical orbit Highly elliptical orbit A highly elliptical orbit (HEO) is an elliptic orbit with high eccentricity, usually referring to one around Earth. Examples of inclined HEO orbits include Molniya orbits, named after the Molniya Soviet communication satellites which used them, and tundra orbits. Such extremely elongated orbits have the advantage of long dwell times at a point in the sky during the approach to, and descent from, apogee. Bodies moving through the long apogee dwell appear to move slowly, and remain at high altitude over high-latitude ground sites for long periods of time. This makes these elliptical orbits useful for communications
Near-Earth object In April 2017, the IAU adopted a revised definition that generally limits meteoroids to a size between 30 µm and 1 m in diameter, but permits the use of the term for any object of any size that caused a meteor, thus leaving the distinction between asteroid and meteoroid blurred. Near-Earth comets (NECs) are objects in a near-Earth orbit with a tail or coma. Comet nuclei are typically less dense than asteroids but they pass Earth at higher relative speeds, thus the impact energy of comet nucleus is slightly larger than that of a similar-sized asteroid. NECs may pose an