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## 2D ORBIT VIEWER

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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