/// <summary>
/// 计算绕地航天器主要的加速度。
/// Computes the acceleration of an Earth orbiting satellite due to
/// - the Earth's harmonic gravity field,
/// - the gravitational perturbations of the Sun and Moon
/// - the solar radiation pressure and
/// - the atmospheric drag
/// </summary>
/// <param name="Mjd_TT"> Mjd_TT Terrestrial Time (Modified Julian Date)</param>
/// <param name="satXyzIcrf"> r 卫星在国际天球参考框架的位置 Satellite position vector in the ICRF/EME2000 system</param>
/// <param name="satVelocityIcrf"> v 卫星在国际天球参考框架的速度 Satellite velocity vector in the ICRF/EME2000 system</param>
/// <param name="Area"> Area Cross-section </param>
/// <param name="mass"> mass 质量 Spacecraft mass</param>
/// <param name="solarRadiPresCoeff"> coefOfRadiation 光压系数 Radiation pressure coefficient</param>
/// <param name="atmDragCoefficient"> coefOfDrag 大气阻力系数 Drag coefficient</param>
/// <returns> Acceleration (a=d^2r/dt^2) in the ICRF/EME2000 system</returns>
public static Geo.Algorithm.Vector AccelerOfMainForces(double Mjd_TT, Geo.Algorithm.Vector satXyzIcrf, Geo.Algorithm.Vector satVelocityIcrf, double Area, double mass, double solarRadiPresCoeff, double atmDragCoefficient)
{
double Mjd_UT1;
Geo.Algorithm.Vector a = new Geo.Algorithm.Vector(3), r_Sun = new Geo.Algorithm.Vector(3), r_Moon = new Geo.Algorithm.Vector(3);
Matrix T = new Matrix(3, 3), E = new Matrix(3, 3);
// Acceleration due to harmonic gravity field
Mjd_UT1 = Mjd_TT;
T = IERS.NutMatrix(Mjd_TT) * IERS.PrecessionMatrix(MJD_J2000, Mjd_TT);
E = IERS.GreenwichHourAngleMatrix(Mjd_UT1) * T;
a = AccelerOfHarmonicGraviFiled(satXyzIcrf, E, Grav.GM, Grav.R_ref, Grav.CS, Grav.n_max, Grav.m_max);
// Luni-solar perturbations
r_Sun = CelestialUtil.Sun(Mjd_TT);
r_Moon = CelestialUtil.Moon(Mjd_TT);
a += AccelerOfPointMass(satXyzIcrf, r_Sun, OrbitConsts.GM_Sun);
a += AccelerOfPointMass(satXyzIcrf, r_Moon, OrbitConsts.GM_Moon);
// Solar radiation pressure
a += CelestialUtil.Illumination(satXyzIcrf, r_Sun) * AccelerOfSolarRadiPressure(satXyzIcrf, r_Sun, Area, mass, solarRadiPresCoeff, OrbitConsts.PressureOfSolarRadiationPerAU, AU);
// Atmospheric drag
a += AccelerDragOfAtmos(Mjd_TT, satXyzIcrf, satVelocityIcrf, T, Area, mass, atmDragCoefficient);
// Acceleration
return(a);
}
static void Main0(string[] args)
{
// Variables
int i; // Loop counter
double MJD_GPS, MJD_TT; // Modified Julian Date (GPS,TT)
double MJD_UTC, MJD_UT1; // Modified Julian Date (UTC,UT1)
Matrix P = new Matrix(3, 3), N = new Matrix(3, 3); // Precession/nutation matrix
Matrix Theta = new Matrix(3, 3); // Sidereal Time matrix
Matrix S = new Matrix(3, 3), dTheta = new Matrix(3, 3); // and derivative
Matrix Pi = new Matrix(3, 3); // Polar motion matrix
Matrix U = new Matrix(3, 3), dU = new Matrix(3, 3); // ICRS to ITRS transformation and derivative
Vector r_WGS = new Vector(3), v_WGS = new Vector(3); // Position/velocity in the Earth-fixed frame
Vector r = new Vector(3), v = new Vector(3); // Position/velocity in the ICRS
Vector y = new Vector(6), Kep = new Vector(6); // Satte vector and Keplerian elements
// Header
var endl = "\r\n";
var info = "Exercise 5-2: Velocity in the Earth-fixed frame"
+ endl + endl;
Console.WriteLine(info);
// Earth Orientation Parameters (UT1-UTC[s],UTC-TAI[s], x["], y["])
// (from IERS Bulletin B #135 and C #16; valid for 1999/03/04 0:00 UTC)
IERS IERS = new IERS(0.6492332, -32.0, 0.06740, 0.24173);
// Date
MJD_GPS = DateUtil.DateToMjd(1999, 03, 04, 0, 0, 0.0);
MJD_UTC = MJD_GPS - IERS.GetGPS_UTC(MJD_GPS) / 86400.0;
MJD_UT1 = MJD_UTC + IERS.GetUT1_UTC(MJD_UTC) / 86400.0;
MJD_TT = MJD_UTC + IERS.GetTT_UTC(MJD_UTC) / 86400.0;
// Earth-fixed state vector of GPS satellite #PRN15
// (from NIMA ephemeris nim09994.eph; WGS84(G873) system)
r_WGS = new Vector(19440.953805e+3, 16881.609273e+3, -6777.115092e+3); // [m]
v_WGS = new Vector(-8111.827456e-1, -2573.799137e-1, -30689.508125e-1); // [m/s]
// ICRS to ITRS transformation matrix and derivative
P = IERS.PrecessionMatrix(OrbitConsts.MJD_J2000, MJD_TT); // IAU 1976 Precession
N = IERS.NutMatrix(MJD_TT); // IAU 1980 Nutation
Theta = IERS.GreenwichHourAngleMatrix(MJD_UT1); // Earth rotation
Pi = IERS.PoleMatrix(MJD_UTC); // Polar motion
S[0, 1] = 1.0; S[1, 0] = -1.0; // Derivative of Earth rotation
dTheta = OrbitConsts.RotationSpeedOfEarth_Rad * S * Theta; // matrix [1/s]
U = Pi * Theta * N * P; // ICRS to ITRS transformation
dU = Pi * dTheta * N * P; // Derivative [1/s]
// Transformation from WGS to ICRS
r = U.Transpose() * r_WGS;
v = U.Transpose() * v_WGS + dU.Transpose() * r_WGS;
// Orbital elements
y = r.Stack(v);
Kep = Kepler.Elements(OrbitConsts.GM_Earth, y);
// Output
info = "Date" + endl + endl
+ " " + DateUtil.MjdToDateTimeString(MJD_GPS) + " GPS" + endl
+ " " + DateUtil.MjdToDateTimeString(MJD_UTC) + " UTC" + endl
+ " " + DateUtil.MjdToDateTimeString(MJD_UT1) + " UT1" + endl
+ " " + DateUtil.MjdToDateTimeString(MJD_TT) + " TT " + endl + endl;
Console.WriteLine(info);
info = "WGS84 (G873) State vector:" + endl + endl;
info += " Position ";
for (i = 0; i < 3; i++)
{
info += String.Format("{0, 10:F6}", r_WGS[i] / 1000.0);
}
;
info += " [km]";
Console.WriteLine(info);
info = " Velocity ";
for (i = 0; i < 3; i++)
{
info += String.Format("{0, 10:F6}", v_WGS[i] / 1000.0);
}
;
info += " [km/s]" + endl + endl;
Console.WriteLine(info);
info = "ICRS-ITRS transformation" + endl + endl
+ String.Format("{0, 10:F6}", U) + endl;
info += "Derivative of ICRS-ITRS transformation [10^(-4)/s]" + endl + endl
+ String.Format("{0, 10:F6}", dU * 1.0e4) + endl;
info += "ICRS State vector:" + endl;
Console.WriteLine(info);
info = " Position ";
for (i = 0; i < 3; i++)
{
info += String.Format("{0, 14:F6}", r[i] / 1000.0);
}
;
info += " [km]";
Console.WriteLine(info);
info = " Velocity ";
for (i = 0; i < 3; i++)
{
info += String.Format("{0, 14:F6}", v[i] / 1000.0);
}
;
info += " [km/s]" + endl + endl;
Console.WriteLine(info);
info = "Orbital elements:" + endl + endl
+ " Semimajor axis " + String.Format("{0, 10:F3}", Kep[0] / 1000.0) + " km" + endl
+ " Eccentricity " + String.Format("{0, 10:F7}", Kep[1]) + endl
+ " Inclination " + String.Format("{0, 10:F3}", Kep[2] * OrbitConsts.DegPerRad) + " deg" + endl
+ " RA ascend. node " + String.Format("{0, 10:F3}", Kep[3] * OrbitConsts.DegPerRad) + " deg" + endl
+ " Arg. of perigee " + String.Format("{0, 10:F3}", Kep[4] * OrbitConsts.DegPerRad) + " deg" + endl
+ " Mean anomaly " + String.Format("{0, 10:F3}", Kep[5] * OrbitConsts.DegPerRad) + " deg" + endl;
Console.WriteLine(info);
Console.ReadKey();
}
static void Main0(string[] args)
{
// Variables
double MJD_UTC; // Modified Julian Date (UTC)
double MJD_UT1; // Modified Julian Date (UTC)
double MJD_TT; // Modified Julian Date (TT)
Matrix P = new Matrix(3, 3); // Precession matrix (ICRS -> mean-of-date)
Matrix N = new Matrix(3, 3); // Nutation matrix (mean-of-date -> true-of-date)
Matrix Theta = new Matrix(3, 3); // Sidereal Time matrix (tod -> pseudo-Earth-fixed)
Matrix Pi = new Matrix(3, 3); // Polar motion matrix (pseudo-Earth-fixed -> ITRS)
// Header
var info = "Exercise 5-1: Transformation from celestial "
+ "to terrestrial reference system" + "\r\n";
Console.WriteLine(info);
// Earth Orientation Parameters (UT1-UTC[s],UTC-TAI[s], x["], y["])
// (from IERS Bulletin B #135 and C #16; valid for 1999/03/04 0:00 UTC)
IERS IERS = new IERS(0.6492332, -32.0, 0.06740, 0.24173);
// Date
MJD_UTC = DateUtil.DateToMjd(1999, 03, 04, 0, 0, 0.0);
MJD_UT1 = MJD_UTC + IERS.GetUT1_UTC(MJD_UTC) / 86400.0;
MJD_TT = MJD_UTC + IERS.GetTT_UTC(MJD_UTC) / 86400.0;
// IAU 1976 Precession
// (ICRF to mean equator and equinox of date)
P = IERS.PrecessionMatrix(OrbitConsts.MJD_J2000, MJD_TT);
// IAU 1980 Nutation
// (Transformation to the true equator and equinox)
N = IERS.NutMatrix(MJD_TT);
// Apparent Sidereal Time
// Rotation about the Celestial Ephemeris Pole
Theta = IERS.GreenwichHourAngleMatrix(MJD_UT1); // Note: here we evaluate the equation of the
// equinoxes with the MJD_UT1 time argument
// (instead of MJD_TT)
// Polar motion
// (Transformation from the CEP to the IRP of the ITRS)
Pi = IERS.PoleMatrix(MJD_UTC); // Note: the time argument of polar motion series
// is not rigorously defined, but any differences
// are negligible
// Output
var endl = "\r\n";
info = "Date" + "\r\n"
+ " " + DateUtil.MjdToDateTimeString(MJD_UTC) + " UTC" + endl
+ " " + DateUtil.MjdToDateTimeString(MJD_UT1) + " UT1" + endl
+ " " + DateUtil.MjdToDateTimeString(MJD_TT) + " TT " + endl + endl + endl;
Console.WriteLine(info);
info = "IAU 1976 Precession matrix (ICRS to tod)" + endl
+ P.ToString();
Console.WriteLine(info);
info = "IAU 1980 Nutation matrix (tod to mod)" + endl
+ N.ToString();
Console.WriteLine(info);
info = "Earth Rotation matrix" + endl
+ Theta.ToString();
Console.WriteLine(info);
info = "Polar motion matrix" + endl
+ Pi.ToString();
Console.WriteLine(info);
info = "ICRS-ITRS transformation" + endl
+ (Pi * Theta * N * P).ToString();
Console.WriteLine(info);
Console.ReadKey();
}