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The apsides refer to the farthest (2) and nearest (3) points reached by an orbiting planetary body (2 and 3) with respect to a primary, or host, body (1). An apsis (from Ancient Greek ἁψίς (hapsís) 'arch, vault'; pl. apsides / ˈ æ p s ɪ ˌ d iː z / AP-sih-deez) [1] [2] is the farthest or nearest point in the orbit of a planetary body about its primary body.
The lunar orbit's major axis – the longest diameter of the orbit, joining its nearest and farthest points, the perigee and apogee, respectively – makes one complete revolution every 8.85 Earth years, or 3,232.6054 days, as it rotates slowly in the same direction as the Moon itself (direct motion) – meaning precesses eastward by 360°.
If the argument of perigee is zero, meaning that perigee and apogee lie in the equatorial plane, then the ground track of the satellite will appear the same above and below the equator (i.e., it will exhibit 180° rotational symmetry about the orbital nodes.) If the argument of perigee is non-zero, however, the satellite will behave differently ...
The argument of perigee is such that apogee occurs on or near the equator. Perigee can be anywhere above the atmosphere, but is usually restricted to a few hundred kilometers above the Earth's surface to reduce launcher delta-V ( Δ V {\displaystyle \Delta V} ) requirements and to limit the orbital lifetime of the spent booster so as to curtail ...
When a full moon occurs near perigee, it glows a little The series of celestial sights will kick off on Friday with the last supermoon of 2024. The term supermoon is more than a viral nickname.
At perigee (closest), since the Moon is up to 14% closer to Earth than at apogee (most distant), it subtends a solid angle which is up to 30% larger. Consequently, given the same phase, the Moon's brightness also varies by up to 30% between apogee and perigee. [208] A full (or new) moon at such a position is called a supermoon. [202] [203] [209]
The exact height of a satellite in a Molniya orbit varies between missions, but a typical orbit will have a perigee altitude of approximately 600 kilometres (370 mi) and an apogee altitude of 39,700 kilometres (24,700 mi), for a semi-major axis of 26,600 kilometres (16,500 mi).
r a is defined as apogee of phasing orbit; r p is defined as perigee of phasing orbit; Finally, the phasing orbit's angular momentum can be found from the equation: = + where h 2 is defined as angular momentum of phasing orbit; r a is defined as apogee of phasing orbit