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Help File

  • HELP. Displays this help screen. To exit, click one of the Exit Help buttons located at the top and bottom of this screen.
  • SEMIMAJOR AXIS. The semimajor axis is defined as half the length of the maximum dimension of an ellipse. It is measured in Astronomical Units (AU), where one AU is the mean distance from the Earth to the Sun.
  • PERICENTER DISTANCE. This pericenter distance is the minimum distance between the orbit and central body whose force determines the orbit. This distance is measured in Astronomical Units (AU).
  • ECCENTRICITY. This parameter is a dimensionless number that ranges from 0 to 1. It is a measure of how much an ellipse deviates from a circle, whose eccentricity is 0. An ellipse with an eccentricity of 1 would essentially be a straight line with a length equal to the twice the semimajor axis of the ellipse.
  • LONGITUDE OF PERICENTER. In 2-D, the longitude of pericenter is the angle measured from a reference point to the pericenter of the orbit with the Sun being the vertex of the angle. In 3-D, the longitude of pericenter is the angle previously mentioned plus the angle of the ascending node which is measured from the same reference point, also having the Sun as the vertex of the angle.
  • TRUE ANOMALY. This parameter specifies the angle between pericenter (the place along the planet's orbit where the planet-Sun distance is smallest) and the starting position of the planet along its orbit. The valid range is 0 to 360 degrees.
  • ECCENTRIC ANOMALY. The Eccentric Anomaly is used to describe the variable length of the radius vector r. The relationship between the eccentric anomaly (E) and r is seen through the following equation: r=a(1-e cos E), where a is the semi-major axis and e is the eccentricity of the ellipse.
  • MEAN ANOMALY. The mean anomaly is the angle formed between a line drawn from the Sun to the pericenter of the ellipse and a line from the Sun to a hypothetical object that has the same orbital period as the real object being studied, but has a constant angular speed.
  • SUBMIT FORM. Send the parameters that you have chosen to the orbital viewer program!
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