Longitude of the ascending node Guide, Meaning , Facts, Information and Description
The
Longitude of the ascending node () is one of the
orbital elements used to specify the
orbit of an object in space. For a sun-orbiting body, it is the angle formed at the
sun from the
First Point of Aries to the body's
ascending node.
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Calculation from state vectors
In astrodynamics for elliptic orbits
longitude of the ascending node is the angle between reference direction (e.g.
vernal equinox) and the
ascending node and can be calculated from
orbital state vectors as:
-
- (if then )
where:
- is the x-component of ,
- is cartesian vector pointing towards the ascending node (i.e. the z-component of is zero).
For equatorial orbits (i.e. orbits with
orbital inclination equal to zero) is undefined. For computations it is then by convention set to zero i.e. "
ascending node" is placed in the reference direction which is equivalent to setting for right-handed system with the x-axis pointing towards the vernal equinox (or other reference direction) and the z-axis pointing upwards.
See also
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