However, the angle ω is less ambiguously known as the argument of periapsis.

It is the sum of the more commonly used true anomaly and argument of periapsis.

Also, the argument of periapsis is undefined.

For the most efficient example mentioned above, targeting an inclination at apoapsis also changes the argument of periapsis.

Because of apsidal precession the Earth's argument of periapsis slowly increases.

It is also known as the argument of periapsis or the argument of perifocus.

In astrodynamics the argument of periapsis ω can be calculated as follows:

Argument of periapsis () defines the angle between the ascending node and the periapsis.

Argument of periapsis (ω)

For the eccentricity and argument of periapsis parameters, eccentricity zero (circular orbit) corresponds to a singularity.

The argument of periapsis (or perihelion in the Solar System) is the angle between a planet's ascending node and its closest approach to its star.

An argument of periapsis of 90 means that the orbiting body will reach periapsis at its northmost distance from the plane of reference.

The argument of periapsis ω, measured in the orbital plane counter-clockwise looking southward, from the ascending node to the periapsis.

Adding the argument of periapsis to the longitude of the ascending node gives the longitude of the periapsis.

This resonance strongly perturbs Namaka's orbit, which has a current precession of the argument of periapsis by about -6.5 per year, implying a precession period of 55 years.

The argument of periapsis (also called argument of perifocus or argument of pericenter), symbolized as ω, is one of the orbital elements of an orbiting body.

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".

This means that inclination is always positive and is entangled with other orbital elements primarily the argument of periapsis which is in turn connected to the longitude of the ascending node.

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.

The angles of inclination, longitude of the ascending node, and argument of periapsis can also be described as the Euler angles defining the orientation of the orbit relative to the reference coordinate system.

The angle of the ascending node, Ω, the inclination, i, and the argument of periapsis, ω, or the longitude of periapsis, ϖ, specify the orientation of the orbit in its plane.

Argument of periapsis defines the orientation of the ellipse in the orbital plane, as an angle measured from the ascending node to the periapsis (the closest point the second body comes to the first during an orbit).

The longitude of the periapsis is the sum of the mean longitude and the mean anomaly ( ) and the mean longitude of the sum of the longitude of the ascending node and the argument of periapsis ( ).