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
Journey of Apollo 15 to the Moon small risk that it could cause the spacecraft to depressurize. It was possible, in an emergency for the crew to spend the cruise back to Earth in their pressurized space suits. The major event of day 4 was Lunar Orbit Insertion (LOI). Occurring behind the Moon, out of contact with the Earth, this engine burn put the spacecraft into orbit around the Moon. It was the first test of the new procedures for using both SPS during a long burn. Loss of Signal (LOS) was at 78 hours, 23 minutes and 31 seconds GET as the spacecraft went behind the