Perigee Argument


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Perigee (Perihelion) Argument

 

in astronomy, a value—orbital element—that determines the orientation of the orbit of a celestial body (the moon, artificial earth satellite, planet, comet, and so on) in the plane of the orbit; it is the angle between the nodal line and the direction of the perigee (perihelion) (see Figure 1). It is calculated from the ascension node of the orbit in the celestial body’s direction of motion.

Figure 1. Perigee (perihelion) and latitude arguments: Ω℧ −nodal line; II-perigee (perihelion); S—celestial body; ΩII-perigee (perihelion) argument; ΩS—latitude argument.