/// <summary>
/// Gets the descending node orbit.
/// </summary>
/// <param name="desc">The desc.</param>
/// <returns><c>true</c> if descending node exists, otherwise <c>false</c></returns>
public bool GetDescendingNode(out Vector3d desc)
{
Vector3d norm = Vector3d.Cross(OrbitNormal, EclipticNormal);
bool s = Vector3d.Dot(Vector3d.Cross(norm, SemiMajorAxisBasis), OrbitNormal) < 0;
double ecc = 0d;
double trueAnom = Vector3d.Angle(norm, -CenterPoint) * KeplerOrbitUtils.Deg2Rad;
if (Eccentricity < 1.0)
{
double cosT = Math.Cos(trueAnom);
ecc = Math.Acos((Eccentricity + cosT) / (1d + Eccentricity * cosT));
if (s)
{
ecc = KeplerOrbitUtils.PI_2 - ecc;
}
}
else if (Eccentricity > 1.0)
{
trueAnom = Vector3d.Angle(norm, CenterPoint) * KeplerOrbitUtils.Deg2Rad;
if (trueAnom >= Math.Acos(-1d / Eccentricity))
{
desc = new Vector3d();
return(false);
}
double cosT = Math.Cos(trueAnom);
ecc = KeplerOrbitUtils.Acosh((Eccentricity + cosT) / (1 + Eccentricity * cosT)) * (s ? -1 : 1);
}
else
{
desc = new Vector3d();
return(false);
}
desc = GetFocalPositionAtEccentricAnomaly(ecc);
return(true);
}
