In astrodynamics, the longitude of the periapsis (symbolized ω) of an orbiting body is the longitude (measured from the point of the vernal equinox) at which the periapsis (closest approach to the central body) would occur if the body's inclination were zero. The longitude of periapsis is a compound angle, with part of it being measured in the plane of reference and the rest being measured in the plane of the orbit. Likewise, any angle derived from the longitude of periapsis (e.g. mean longitude and true longitude) will also be compound. Astrodynamics is the study of the motion of rockets, missiles, and space vehicles, as determined from Sir Isaac Newtons laws of motion and his law of universal gravitation. ... Longitude is the east-west geographic coordinate measurement most commonly utilized in cartography and global navigation. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... For the science fiction novella by William Shunn, see Inclination (novella). ... In celestial mechanics, the plane of reference is the plane from which orbital elements are defined. ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... In astrodynamics or celestial dynamics mean longitude of an orbiting body is . ... In astrodynamics true longitude is a . ...
Calculation from state vectors
ω can be calculated from longitude of ascending node Ω and argument of periapsis ω: The Longitude of the ascending node () is one of the orbital elements used to specify the orbit of an object in space. ... The argument of periapsis (ω) is the orbital element describing the angle between an orbiting bodys ascending node (the point where the body crosses the plane of reference from South to North) and its periapsis (the point of closest approach to the central body), measured in the orbital plane and...
ω = Ω + ω
which are derived from orbital state vectors. In astrodynamics or celestial dynamics orbital state vectors (sometimes State Vectors) are vectors of position () and velocity () that together with their time (epoch) () uniquely determine the state of an orbiting body. ...
As an object orbits another object, periapsis is that point at which the orbiting object is closest to the object being orbited; apoapsis is that point at which the orbiting object is farthest from the object beinn orbited.
The point where the orbiting body is closest to Earth is the perigee, called periapsis (less properly, "perifocus" or "pericentron") when the orbit is around a body other than Earth.
The point on the orbit closest to the attracting body is the periapsis.
The three orbital elements that describe an orbit's orientation are the inclination (i), the longitude of the ascending node (Ω), and the argument of the periapsis (ω).
The longitude of the ascending node is the angle in the reference plane between the equinox and the ascending node.
The argument of the periapsis measures the angular displacement in the plane of the orbit between the ascending node and the line that passes through the center of the orbit (C) and the periapsis (P).
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