perigee

noun

Etymology: From French périgée via Latin perigeum, perigaeum, ultimately from Ancient Greek περί (perí, “near”) + γῆ (gê, “Earth”).

1. The point, in an orbit about the Earth, that is closest to the Earth: the periapsis of an Earth orbiter.

   “As the moon wheels around Earth every 28 days and shows us a progressively greater and then stingier slice of its sun-lightened face, the distance between the moon and Earth changes, too. At the nearest point along its egg-shaped orbit, its perigee, the moon may be 26,000 miles closer to us than it is at its far point.”

2. The point, in an orbit about any planet, that is closest to the planet: the periapsis of any satellite.

   “Conjunctions of I and II [Io and Europa] occur when they are near perigee and apogee respectively; conjunctions of II and III [Europa and Ganymede] occur when II [Europa] is near perigee.”

   “The resolution of the images obtained by this American probe [Messenger] will depend on its altitude [above Mercury] at any one time: about ten meters at perigee (200km altitude), but only one 1 km at apogee (15000km).”

3. The point, in any trajectory of an object in space, where it is closest to the Earth.