/// <summary>
/// Orbit foo, this finds the nodes of two orbits
/// </summary>
/// <returns>
/// The true anomaly of the ascending node(descing node is 180degrees off)
/// </returns>
/// <param name='orbit'>
/// Orbit.
/// </param>
/// <param name='tgtorbit'>
/// Target Orbit
/// </param>
public static double FindAN(this Orbit orbit, Orbit tgtorbit)
{
Vector3d normal = ARUtils.swapYZ(orbit.GetOrbitNormal());
Vector3d targetNormal = ARUtils.swapYZ(tgtorbit.GetOrbitNormal());
Vector3d vectorToAN = Vector3d.Cross(normal, targetNormal);
Vector3d vectorToPe = ARUtils.swapYZ(orbit.eccVec);
double angleFromPe = Vector3d.Angle(vectorToPe, vectorToAN);
//If the AN is actually during the infalling part of the orbit then we need to add 180 to
//angle from Pe to get the true anomaly. Test this by taking the the cross product of the
//orbit normal and vector to the periapsis. This gives a vector that points to center of the
//outgoing side of the orbit. If vectorToAN is more than 90 degrees from this vector, it occurs
//during the infalling part of the orbit.
if (Math.Abs(Vector3d.Angle(vectorToAN, Vector3d.Cross(vectorToPe, normal))) < 90)
{
return(angleFromPe);
}
else
{
return(360 - angleFromPe);
}
/* double rad = Math.PI/180;
* double Lan1 = orbit.LAN;
* double inc1 = orbit.inclination;
* double Lan2 = tgtorbit.LAN;
* double inc2 = tgtorbit.inclination;
*
* //see braeunig.us/space... cross product of two orbital planes gives the node location
* var a = new Vector3d(Math.Sin(inc1*rad)*Math.Cos(Lan1*rad), Math.Sin(inc1*rad)*Math.Sin(Lan1*rad),
* Math.Cos(inc1*rad));
* var b = new Vector3d(Math.Sin(inc2*rad)*Math.Cos(Lan2*rad), Math.Sin(inc2*rad)*Math.Sin(Lan2*rad),
* Math.Cos(inc2*rad));
* var c = new Vector3d(0, 0, 0);
* c = Vector3d.Cross(a, b);
* var coord = new double[] {0, 0};
* coord = LatLonofVector(c); //get the coordinates lat/lon of the ascending node
* double lat = coord[0];
* double lon = coord[1];
*
* //go look at the diagrams at braeunig.us/space
* double α = lon - Lan1; //its all greek to me
* if (α < 0) α += 360;
* double λ = Math.Atan(Math.Tan(α*rad)/Math.Cos(inc1*rad))/rad;
* double x = 180 + (λ - orbit.argumentOfPeriapsis);
* if (x > 360) return 360 - x;
* else return x;*/
}
