Fig. 1: Diagram of orbital elements, including the argument of periapsis (ω).
Part of a series on
Astrodynamics
Orbital mechanics
Orbital elements
Apsis
Argument of periapsis
Eccentricity
Inclination
Mean anomaly
Orbital nodes
Semi-major axis
True anomaly
Types of two-body orbits by eccentricity
Circular orbit
Elliptic orbit
Transfer orbit
(Hohmann transfer orbit
Bi-elliptic transfer orbit)
Parabolic orbit
Hyperbolic orbit
Radial orbit
Decaying orbit
Equations
Dynamical friction
Escape velocity
Kepler's equation
Kepler's laws of planetary motion
Orbital period
Orbital velocity
Surface gravity
Specific orbital energy
Vis-viva equation
Celestial mechanics
Gravitational influences
Barycenter
Hill sphere
Perturbations
Sphere of influence
N-body orbits
Lagrangian points
(Halo orbits)
Lissajous orbits
Lyapunov orbits
Engineering and efficiency
Preflight engineering
Mass ratio
Payload fraction
Propellant mass fraction
Tsiolkovsky rocket equation
Efficiency measures
Gravity assist
Oberth effect
Propulsive maneuvers
Orbital maneuver
Orbit insertion
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The argument of periapsis (also called argument of perifocus or argument of pericenter), symbolized as ω (omega), is one of the orbital elements of an orbiting body. Parametrically, ω is the angle from the body's ascending node to its periapsis, measured in the direction of motion.
For specific types of orbits, terms such as argument of perihelion (for heliocentric orbits), argument of perigee (for geocentric orbits), argument of periastron (for orbits around stars), and so on, may be used (see apsis for more information).
An argument of periapsis of 0° means that the orbiting body will be at its closest approach to the central body at the same moment that it crosses the plane of reference from South to North. An argument of periapsis of 90° means that the orbiting body will reach periapsis at its northmost distance from the plane of reference.
Adding the argument of periapsis to the longitude of the ascending node gives the longitude of the periapsis. However, especially in discussions of binary stars and exoplanets, the terms "longitude of periapsis" or "longitude of periastron" are often used synonymously with "argument of periapsis".
and 22 Related for: Argument of periapsis information
longitude of perihelion ϖ, which is the sum of the longitude of the ascending node Ω, and the argumentof perihelion ω. The longitude ofperiapsis is a compound...
of the more commonly used true anomaly and argumentofperiapsis. u = ν + ω {\displaystyle u=\nu +\omega } where u {\displaystyle u} is the argument of...
Argumentofperiapsis (ω) defines the orientation of the ellipse in the orbital plane, as an angle measured from the ascending node to the periapsis (the...
body will be at periapsis. If this is less than planet's radius an impact should be expected. The distance of closest approach, or periapsis distance, is...
1) at the periapsis point, or 2) at the apoapsis point (compare both graphics, second figure). The line of apsides denotes the distance of the line that...
and closest (periapsis) from its primary body. The apsidal precession is the first time derivative of the argumentofperiapsis, one of the six main orbital...
defines the position of a body moving along a Keplerian orbit. It is the angle between the direction ofperiapsis and the current position of the body, as seen...
point in its orbit. The maximum (instantaneous) orbital speed occurs at periapsis (perigee, perihelion, etc.), while the minimum speed for objects in closed...
changes the argumentofperiapsis. However, targeting in this manner limits the mission designer to changing the plane only along the line of apsides.[citation...
the periapsis in the first place (and truly circular orbits have no periapsis at all). Furthermore, the equation was derived on the assumption of an elliptical...
periapsisof an elliptical orbit) accelerates along its direction of travel to escape velocity, the point of acceleration will form the periapsisof the...
the time ofperiapsis passage μ {\displaystyle \mu } is the standard gravitational parameter p {\displaystyle p} is the semi-latus rectum of the trajectory...
vector to change continuously as opposed to the eccentricity and argumentofperiapsis parameters for which eccentricity zero (circular orbit) corresponds...
of a circle. In this case, not only the distance, but also the speed, angular speed, potential and kinetic energy are constant. There is no periapsis...
and the apogee burn (or apogee kick); more generally, they are labelled periapsis and apoapsis burns. Alternately, the second burn to circularize the orbit...
other time. If an impulsive burn of Δv is performed at periapsis in a parabolic orbit, then the velocity at periapsis before the burn is equal to the escape...
between two passages of an object at its periapsis (in the case of the planets in the Solar System, called the perihelion), the point of its closest approach...
at the time of the burn. Therefore the maximum kinetic energy is obtained when the burn occurs at the vehicle's maximum velocity (periapsis). The Oberth...
ellipse extends above the surface, plus the periapsis distance (the distance the ellipse extends beyond the center of the Earth). For the Earth and a {\displaystyle...
farthest distance of the orbit to the center of mass of the system, which is a focus of the ellipse. rp is the radius at periapsis (or "perifocus" etc...
mean anomaly is the fraction of an elliptical orbit's period that has elapsed since the orbiting body passed periapsis, expressed as an angle which can...
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