/// <summary>
/// Gets the descending node of 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)
{
var norm = CelestialBodyUtils.CrossProduct(OrbitNormal, EclipticNormal);
var s = CelestialBodyUtils.DotProduct(CelestialBodyUtils.CrossProduct(norm, SemiMajorAxisBasis), OrbitNormal) < 0;
var ecc = 0d;
var trueAnom = Vector3d.Angle(norm, -CenterPoint) * Mathd.Deg2Rad;
if (Eccentricity < 1)
{
var cosT = Math.Cos(trueAnom);
ecc = Math.Acos((Eccentricity + cosT) / (1d + Eccentricity * cosT));
if (s)
{
ecc = Mathd.PI_2 - ecc;
}
}
else
{
trueAnom = Vector3d.Angle(norm, CenterPoint) * Mathd.Deg2Rad;
if (trueAnom >= Mathd.Acos(-1d / Eccentricity))
{
desc = new Vector3d();
return(false);
}
var cosT = Math.Cos(trueAnom);
ecc = CelestialBodyUtils.Acosh((Eccentricity + cosT) / (1 + Eccentricity * cosT)) * (s ? -1 : 1);
}
desc = GetFocalPositionAtEccentricAnomaly(ecc);
return(true);
}
public bool GetAscendingNode(out Vector3d asc)
{
var norm = CelestialBodyUtils.CrossProduct(orbitNormal, eclipticNormal);
var s = CelestialBodyUtils.DotProduct(CelestialBodyUtils.CrossProduct(norm, semiMajorAxisBasis), orbitNormal) < 0;
var ecc = 0d;
var trueAnom = Vector3d.Angle(norm, centerPoint) * Mathd.Deg2Rad;
if (eccentricity < 1)
{
var cosT = System.Math.Cos(trueAnom);
ecc = System.Math.Acos((eccentricity + cosT) / (1d + eccentricity * cosT));
if (!s)
{
ecc = Mathd.PI_2 - ecc;
}
}
else
{
trueAnom = Vector3d.Angle(-norm, centerPoint) * Mathd.Deg2Rad;
if (trueAnom >= Mathd.Acos(-1d / eccentricity))
{
asc = new Vector3d();
return(false);
}
var cosT = System.Math.Cos(trueAnom);
ecc = CelestialBodyUtils.Acosh((eccentricity + cosT) / (1 + eccentricity * cosT)) * (!s ? -1 : 1);
}
asc = GetFocalPositionAtEccentricAnomaly(ecc);
return(true);
}
public static double ConvertTrueToEccentricAnomaly(double trueAnomaly, double eccentricity)
{
trueAnomaly = trueAnomaly % Mathd.PI_2;
if (eccentricity < 1d)
{
if (trueAnomaly < 0)
{
trueAnomaly = trueAnomaly + Mathd.PI_2;
}
var cosT2 = System.Math.Cos(trueAnomaly);
var eccAnom = System.Math.Acos((eccentricity + cosT2) / (1d + eccentricity * cosT2));
if (trueAnomaly > Mathd.PI)
{
eccAnom = Mathd.PI_2 - eccAnom;
}
return(eccAnom);
}
else
{
var cosT = System.Math.Cos(trueAnomaly);
var eccAnom = CelestialBodyUtils.Acosh((eccentricity + cosT) / (1d + eccentricity * cosT)) * System.Math.Sign(trueAnomaly);
return(eccAnom);
}
}
