// ///////////////////////////////////////////////////////////////////
// Calculate the ECI coordinates of the location "geo" at time "date".
// Assumes geo coordinates are km-based.
// Assumes the earth is an oblate spheroid as defined in WGS '72.
// Reference: The 1992 Astronomical Almanac, page K11
// Reference: www.celestrak.com (Dr. TS Kelso)
public Eci(CoordGeo geo, Julian date)
{
m_VecUnits = VecUnits.UNITS_KM;
double mfactor = Globals.TWOPI * (Globals.OMEGA_E / Globals.SEC_PER_DAY);
double lat = geo.m_Lat;
double lon = geo.m_Lon;
double alt = geo.Altitude.Kilometers;
// Calculate Local Mean Sidereal Time (theta)
double theta = date.toLMST(lon);
double c = 1.0 / Math.Sqrt(1.0 + Globals.F * (Globals.F - 2.0) * Globals.Sqr(Math.Sin(lat)));
double s = Globals.Sqr(1.0 - Globals.F) * c;
double achcp = (Globals.XKMPER * c + alt) * Math.Cos(lat);
m_date = date;
m_pos = new Vector();
m_pos.X = achcp * Math.Cos(theta); // km
m_pos.Y = achcp * Math.Sin(theta); // km
m_pos.Z = (Globals.XKMPER * s + alt) * Math.Sin(lat); // km
m_pos.W = Math.Sqrt(Globals.Sqr(m_pos.X) +
Globals.Sqr(m_pos.Y) +
Globals.Sqr(m_pos.Z)); // range, km
m_vel = new Vector();
m_vel.X = -mfactor * m_pos.Y; // km / sec
m_vel.Y = mfactor * m_pos.X;
m_vel.Z = 0.0;
m_vel.W = Math.Sqrt(Globals.Sqr(m_vel.X) + // range rate km/sec^2
Globals.Sqr(m_vel.Y));
}
public Eci(Vector pos, Vector vel, Julian date, bool IsAeUnits)
{
m_pos = pos;
m_vel = vel;
m_date = date;
m_VecUnits = (IsAeUnits ? VecUnits.UNITS_AE : VecUnits.UNITS_NONE);
}
public Eci()
{
m_VecUnits = VecUnits.UNITS_NONE;
}
public void setUnitsKm()
{
m_VecUnits = VecUnits.UNITS_KM;
}
public void setUnitsAe()
{
m_VecUnits = VecUnits.UNITS_AE;
}
// ///////////////////////////////////////////////////////////////////////////
// Convert the position and velocity vector units from Globals.AE-based units
// to kilometer based units.
public void ae2km()
{
if (UnitsAreAe())
{
MulPos(Globals.XKMPER / Globals.AE); // km
MulVel((Globals.XKMPER / Globals.AE) * (Globals.MIN_PER_DAY / 86400)); // km/sec
m_VecUnits = VecUnits.UNITS_KM;
}
}
