SolarPointedAttitudeLaw 4.4

SolarPointedAttitudeLaw 4.4

public class SolarPointedAttitudeLaw {

   public static void main(String[] args) throws PatriusException, IOException, URISyntaxException {
       
       // Patrius Dataset initialization (needed for example to get the UTC time
       PatriusDataset.addResourcesFromPatriusDataset() ;

       // Recovery of the UTC time scale using a "factory" (not to duplicate such unique object)
       final TimeScale TUC = TimeScalesFactory.getUTC();
       
       // Date of the orbit given in UTC time scale)
       final AbsoluteDate date = new AbsoluteDate("2010-01-01T12:00:00.000", TUC);
       
       // Getting the frame with wich will defined the orbit parameters
       // As for time scale, we will use also a "factory".
       final Frame GCRF = FramesFactory.getGCRF();

       // Initial orbit
       final double sma = 7200.e+3;
       final double exc = 0.01;
       final double inc = FastMath.toRadians(98.);
       final double pa = FastMath.toRadians(0.);
       final double raan = FastMath.toRadians(0.);
       final double anm = FastMath.toRadians(0.);
       final double MU = Constants.WGS84_EARTH_MU;
       
       final KeplerianParameters par = new KeplerianParameters(sma, exc, inc, pa, raan, anm, PositionAngle.MEAN, MU);
       final Orbit iniOrbit = new KeplerianOrbit(par, GCRF, date);
       
       // Using the Meeus model for the Sun.
       final CelestialBody sun = new MeeusSun();

       // Building an attitude law
       final Vector3D firstAxis = new Vector3D(1., 0., 0.);
       final Vector3D secondAxis = new Vector3D(0., 1., 0.);
       final AttitudeLaw attitudeLaw = new SunPointing(sun, firstAxis, secondAxis, sun);
       final Attitude att = attitudeLaw.getAttitude(iniOrbit);
       
       // Printing attitude
       final double psi  = att.getRotation().getAngles(RotationOrder.ZYX)[0];
       final double teta = att.getRotation().getAngles(RotationOrder.ZYX)[1];

       System.out.println("Psi  / GCRF  = "+FastMath.toDegrees(psi)+" deg");
       System.out.println("Teta / GCRF = "+FastMath.toDegrees(teta)+" deg");
       
       // Coordinates of the Sun vs GCRF at the same date
       PVCoordinates pv = sun.getPVCoordinates(date, GCRF);
       final Vector3D sunPos = pv.getPosition();
       
       // Direction of the Sun from the cdg of the satellite
       final Vector3D satPos = iniOrbit.getPVCoordinates(GCRF).getPosition();
       final Rotation sunDir = new Rotation(Vector3D.PLUS_I, sunPos.subtract(satPos));
       
       final double psiSun  = sunDir.getAngles(RotationOrder.ZYX)[0];
       final double tetaSun = sunDir.getAngles(RotationOrder.ZYX)[1];

       System.out.println();
       System.out.println("Psi  / GCRF  = "+FastMath.toDegrees(psiSun)+" deg");
       System.out.println("Teta / GCRF = "+FastMath.toDegrees(tetaSun)+" deg");
       
       System.out.println();
       System.out.println("Delta Psi  = "+FastMath.toDegrees(psiSun-psi)+" deg");
       System.out.println("Delta Teta = "+FastMath.toDegrees(tetaSun-teta)+" deg");
       
   }

}