Orbit of the Moon the Moon varies as it orbits Earth and hence is not always equal to the Moon's rotational velocity. When the Moon is at its perigee, its rotation is slower than its orbital motion, and this allows us to see up to eight degrees of longitude of its eastern (right) far side. Conversely, when the Moon reaches its apogee, its rotation is faster than its orbital motion and this reveals eight degrees of longitude of its western (left) far side. This is referred to as "longitudinal libration". Because the lunar orbit is also inclined to Earth's ecliptic plane by 5.1°, the
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