/// <summary>
/// 计算坐标
/// </summary>
/// <param name="timeFromReffer"></param>
/// <param name="param"></param>
/// <returns></returns>
public static MotionState GetSatPos(double timeFromReffer, KeplerEphemerisParam param)
{
return(GetSatPos(
timeFromReffer,
param.Inclination,
param.LongOfAscension,
param.SqrtA * param.SqrtA,
param.Eccentricity,
param.ArgumentOfPerigee,
param.MeanAnomaly));
}
/// <summary>
/// 计算开普勒根数
/// </summary>
/// <param name="pos"></param>
/// <param name="velocity"></param>
/// <returns></returns>
public static KeplerEphemerisParam GetKeplerEphemerisParam(XYZ pos, XYZ velocity)
{
//2.6.1.1 计算轨道倾角i和升交点赤经Ω
XYZ hXyz = pos.Cross(velocity);
double hLen = hXyz.Length;
double r = pos.Length;
double vv = velocity.Dot(velocity);
//计算轨道倾角
//double ABLen = Math.Sqrt(hXyz.X * hXyz.X + hXyz.Y * hXyz.Y);
//double i = Math.Atan2(ABLen, hXyz.Z);
double i = Math.Acos(hXyz.Z / hLen); //表示在Z轴上的投影，与上结果计算一致
//double includedAngle = hXyz.GetIncludedAngle(new XYZ(0, 0, 1));//轨道倾角为两个平面法向量的夹角
//计算升交点赤经
double Ω = Math.Atan2(hXyz.X, -hXyz.Y);
//2.6.1.2 计算轨道长半轴a，
double a = 1 / (2 / r - vv / GM); //由活力公式计算
double sqrtA = Math.Sqrt(a);
double n = Math.Sqrt(GM) / (sqrtA * sqrtA * sqrtA); //平运动角速度n
//离心率e和平近点交M
double rdotv = pos.Dot(velocity);
double eCosE = 1 - r / a;
double eSinE = rdotv / Math.Sqrt(GM * a);
double e = Math.Sqrt(eSinE * eSinE + eCosE * eCosE); //离心率e
double E = Math.Atan2(eSinE, eCosE); //偏近点角E
double M = E - eSinE; //平近点角
//2.6.1.3 计算近升角距ω
XYZ eXyz = velocity.Cross(hXyz) / GM - pos.UnitVector();
double ww = Math.Atan2(eXyz.Z, (eXyz.Y * Math.Sin(Ω) + eXyz.X * Math.Cos(Ω)) * Math.Sin(i));
double u = Math.Atan2(pos.Z, (pos.Y * Math.Sin(Ω) + pos.X * Math.Cos(Ω)) * Math.Sin(i));
double ff = u - ww;//真近点角
KeplerEphemerisParam param = new KeplerEphemerisParam
{
ArgumentOfPerigee = ww,
Eccentricity = e,
Inclination = i,
LongOfAscension = Ω,
MeanAnomaly = M,
SqrtA = sqrtA
};
return(param);
}
