Argument of Perihelion is an angle measured along the orbit of a planet in the solar system from the ascending node. It is one of the orbital element. It specifies the orbit's major axis direction around the sun. It is also referred to as argument of perifocus or argument of pericenter represented by ω. For earth's orbit, it is termed as the Argument of Perigee. Earth has Argument of Perihelion value as 1.9933026 radians.