//Returns the next time at which a will cross its descending node with b.
//For elliptical orbits this is a time between UT and UT + a.period.
//For hyperbolic orbits this can be any time, including a time in the past if
//the descending node is in the past.
//NOTE: this function will throw an ArgumentException if a is a hyperbolic orbit and the "descending node"
//occurs at a true anomaly that a does not actually ever attain
public static double TimeOfDescendingNode(this Orbit a, Orbit b, double UT)
{
if (a.eccentricity >= 1.0)
{
return(UT);
}
else
{
return(a.TimeOfTrueAnomaly(a.DescendingNodeTrueAnomaly(b), UT));
}
}
/// Return the UT of the AN or DN, whichever is sooner
public static double TimeOfPlaneChange(Orbit currentOrbit, Orbit targetOrbit, double minTime, out bool ascending)
{
double ascTime = currentOrbit.TimeOfTrueAnomaly(currentOrbit.AscendingNodeTrueAnomaly(targetOrbit), minTime),
descTime = currentOrbit.TimeOfTrueAnomaly(currentOrbit.DescendingNodeTrueAnomaly(targetOrbit), minTime);
if (ascTime > minTime && ascTime < descTime)
{
ascending = true;
return(ascTime);
}
else
{
ascending = false;
return(descTime);
}
}
//Returns the next time at which a will cross its descending node with b.
//For elliptical orbits this is a time between UT and UT + a.period.
//For hyperbolic orbits this can be any time, including a time in the past if
//the descending node is in the past.
//NOTE: this function will throw an ArgumentException if a is a hyperbolic orbit and the "descending node"
//occurs at a true anomaly that a does not actually ever attain
public static double TimeOfDescendingNode(this Orbit a, Orbit b, double UT)
{
return(a.TimeOfTrueAnomaly(a.DescendingNodeTrueAnomaly(b), UT));
}
//Returns whether a has a descending node with b. This can be false
//if a is hyperbolic and the would-be descending node is within the opening
//angle of the hyperbola.
public static bool DescendingNodeExists(this Orbit a, Orbit b)
{
return(Math.Abs(MuUtils.ClampDegrees180(a.DescendingNodeTrueAnomaly(b))) <= a.MaximumTrueAnomaly());
}
