Dictionary

periapsis en · NOUN

Pronunciation

• (US) audio

Etymology

Etymology tree Proto-Indo-European *per-der. Ancient Greek περῐ́ (perĭ́)der. English peri- English apsis English periapsis From peri- + apsis.

Meanings

1. The point of a body's (elliptical) orbit in a 2-body gravitational system such that the distance between the two bodies (measured from their respective centres of mass) is at its minimum.
   • We don't always want to burn near periapsis. Suppose we want to change the height at periapsis. The most efficient place to change the radius of periapsis is at apoapsis. Consider applying #92;Deltav at some other point in the orbit. In this case both periapsis and apoapsis will change. If we apply the #92;Deltav tangentially at apoapsis, all of the #92;Deltav will go into changing periapsis, and vice versa. 2001, D. A. Vallado, Fundamentals of Astrodynamics and Applications, Springer, page 325:
   • 2004, R. S. Saunders, et al., Mars Odyssey Mission, C. T. Russell (editor), 2001 Mars Odyssey, Kluwer Academic Publishers, page 34, The main aerobraking phase began once the point of the spacecraft's periapsis had been lowered to within 110 km above the Martian surface.
   • 1983, Richard O. Fimmel, Laurence Colin, Eric Burgess, Pioneer Venus, NASA SP-461, page 109, Figure 5-19. Sun-Venus-Orbiter geometry illustrates how the periapsis moves around the planet during the Venusian sidereal year to sample day and night hemispheres. Because the planet rotates in a retrograde direction, it takes more than one Venusian sidereal year for periapsis to move over all longitudes of the planet (as explained in text).
2. The minimum distance between the two bodies in such a system.

Forms

Antonyms

apoapsis

Deriveds

argument of periapsis · longitude of periapsis

Hypernyms

apsis

Relateds

periposeidion · perihermion · periselene · perigalacticon · perikron · perisaturnium · perinigricon · pericynthion · perilune · periastron · perijove · perimelasma · periareion · pericenter · pericentre · peribothron · perihelion · perikrone · perigee

Synonyms

periapse · pericenter

Translations (9)

pt periapside (Translations) · bg периапсида (Translations) · ga pearaipsis (Translations) · el περίαψη (Translations) · fr périapse (Translations) · nl periapsis (Translations) · fr périapside (Translations) · fi periapsis (Translations) · nl perifocus (Translations)