Admin : Page créée avec « public class SequenceOfAttitudeLaws { public static void main(String[] args) throws PatriusException { // Patrius Datas... »

2018-12-18T10:19:25Z

Page créée avec « <syntaxhighlight lang="java"> public class SequenceOfAttitudeLaws { public static void main(String[] args) throws PatriusException { // Patrius Datas... »

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<syntaxhighlight lang="java">
public class SequenceOfAttitudeLaws {

public static void main(String[] args) throws PatriusException {

// 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 iniDate = 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(90.);
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, iniDate);

// Using the Meeus model for the Sun.
final CelestialBody sun = new MeeusSun();
final double sunRadius = Constants.SUN_RADIUS;

// Definition of the Earth ellipsoid for later atmospheric density computation
final Frame ITRF = FramesFactory.getITRF();
final double earthRadius = Constants.WGS84_EARTH_EQUATORIAL_RADIUS;
final GeometricBodyShape earth = new ExtendedOneAxisEllipsoid(earthRadius, Constants.WGS84_EARTH_FLATTENING, ITRF, "EARTH");

// Initializing attitude sequence
final AttitudesSequence seqAtt = new AttitudesSequence();

// Building a first attitude law (Sun pointing)
final Vector3D firstAxis = new Vector3D(1., 0., 0.);
final Vector3D secondAxis = new Vector3D(0., 1., 0.);
final AttitudeLaw sunPointingLaw = new SunPointing(sun, firstAxis, secondAxis, sun);

// Building a second attitude law (LVLH)
final AttitudeLaw lvlhLaw = new LofOffset(LOFType.LVLH);

// Events that will switch from a law to another
final double maxCheck = 10.;
final double threshold = 1.e-3;
final EventDetector eventEntryEclipse = new EclipseDetector(sun, sunRadius, earth, earthRadius, 0,
maxCheck, threshold, Action.RESET_STATE, Action.RESET_STATE);
final EventDetector eventExitEclipse = new EclipseDetector(sun, sunRadius, earth, earthRadius, 0,
maxCheck, threshold, Action.RESET_STATE, Action.RESET_STATE);

//Adding switches
seqAtt.addSwitchingCondition(lvlhLaw, eventEntryEclipse, true, false, sunPointingLaw);
seqAtt.addSwitchingCondition(sunPointingLaw, eventExitEclipse, false, true, lvlhLaw);

}
}
</syntaxhighlight>

<br/>
If you want to check some results seeing attitude values along the propagation, you may call, for example, this method:

<syntaxhighlight lang="java">
public static void testByPropagation ( final Orbit iniOrbit, final AttitudesSequence seqAtt, final CelestialBody sun ) throws PatriusException {

// We create a spacecratftstate
final SpacecraftState iniState = new SpacecraftState(iniOrbit);

// Initialization of the Runge Kutta integrator with a 2 s step
final double pasRk = 2.;
final FirstOrderIntegrator integrator = new ClassicalRungeKuttaIntegrator(pasRk);

// Initialization of the propagator
final NumericalPropagator propagator = new NumericalPropagator(integrator);
propagator.resetInitialState(iniState);

// Forcing integration using cartesian equations
propagator.setOrbitType(OrbitType.CARTESIAN);

// Adding the attitude sequence
propagator.setAttitudeProvider(seqAtt);
seqAtt.registerSwitchEvents(propagator);

// Loop every 10 mn ...
final double step = 600.;
final double epsilon = 1.e-12;
for (int i = 1; i <= 20; i++) {

AbsoluteDate date = iniOrbit.getDate().shiftedBy(i*step);

final SpacecraftState state = propagator.propagate(date);

// Attitude in LVLH
final Attitude attLVLH = state.getAttitude(LOFType.LVLH);
final double psiLVLH = attLVLH.getRotation().getAngles(RotationOrder.ZYX)[0];
final double tetaLVLH = attLVLH.getRotation().getAngles(RotationOrder.ZYX)[1];

// Attitude in GCRF
final Attitude attGCRF = state.getAttitude();
final double psiGCRF = attGCRF.getRotation().getAngles(RotationOrder.ZYX)[0];
final double tetaGCRF = attGCRF.getRotation().getAngles(RotationOrder.ZYX)[1];

// Direction of the Sun from the cdg of the satellite
final Vector3D sunPos = sun.getPVCoordinates(date, FramesFactory.getGCRF()).getPosition();
final Vector3D satPos = state.getPVCoordinates().getPosition();
final Rotation sunDir = new Rotation(Vector3D.PLUS_I, sunPos.subtract(satPos));

// Sun direction
final double psiSun = sunDir.getAngles(RotationOrder.ZYX)[0];
final double tetaSun = sunDir.getAngles(RotationOrder.ZYX)[1];

if ( (FastMath.abs(psiLVLH) < epsilon) || (FastMath.abs(tetaLVLH) < epsilon) ) {
System.out.println(date+" => LVLH mode");
} else {
System.out.println(date+" => Sun pointing mode");
System.out.println(" Delta Psi = "+FastMath.toDegrees(psiSun-psiGCRF)+" deg");
System.out.println(" Delta Teta = "+FastMath.toDegrees(tetaSun-tetaGCRF)+" deg");
}

}
</syntaxhighlight>

SequenceOfAttitudes 4.1 - Historique des versions

Admin : Page créée avec « public class SequenceOfAttitudeLaws { public static void main(String[] args) throws PatriusException { // Patrius Datas... »

Admin : Page créée avec « public class SequenceOfAttitudeLaws { public static void main(String[] args) throws PatriusException { // Patrius Datas... »