use of org.orekit.attitudes.AttitudesSequence in project Orekit by CS-SI.
the class EarthObservation method main.
/**
* Program entry point.
* @param args program arguments (unused here)
*/
public static void main(String[] args) {
try {
// configure Orekit
File home = new File(System.getProperty("user.home"));
File orekitData = new File(home, "orekit-data");
if (!orekitData.exists()) {
System.err.format(Locale.US, "Failed to find %s folder%n", orekitData.getAbsolutePath());
System.err.format(Locale.US, "You need to download %s from the %s page and unzip it in %s for this tutorial to work%n", "orekit-data.zip", "https://www.orekit.org/forge/projects/orekit/files", home.getAbsolutePath());
System.exit(1);
}
DataProvidersManager manager = DataProvidersManager.getInstance();
manager.addProvider(new DirectoryCrawler(orekitData));
final SortedSet<String> output = new TreeSet<String>();
// Initial state definition : date, orbit
final AbsoluteDate initialDate = new AbsoluteDate(2004, 01, 01, 23, 30, 00.000, TimeScalesFactory.getUTC());
final Vector3D position = new Vector3D(-6142438.668, 3492467.560, -25767.25680);
final Vector3D velocity = new Vector3D(505.8479685, 942.7809215, 7435.922231);
final Orbit initialOrbit = new KeplerianOrbit(new PVCoordinates(position, velocity), FramesFactory.getEME2000(), initialDate, Constants.EIGEN5C_EARTH_MU);
// Attitudes sequence definition
final AttitudeProvider dayObservationLaw = new LofOffset(initialOrbit.getFrame(), LOFType.VVLH, RotationOrder.XYZ, FastMath.toRadians(20), FastMath.toRadians(40), 0);
final AttitudeProvider nightRestingLaw = new LofOffset(initialOrbit.getFrame(), LOFType.VVLH);
final PVCoordinatesProvider sun = CelestialBodyFactory.getSun();
final PVCoordinatesProvider earth = CelestialBodyFactory.getEarth();
final EventDetector dayNightEvent = new EclipseDetector(sun, 696000000., earth, Constants.WGS84_EARTH_EQUATORIAL_RADIUS).withHandler(new ContinueOnEvent<EclipseDetector>());
final EventDetector nightDayEvent = new EclipseDetector(sun, 696000000., earth, Constants.WGS84_EARTH_EQUATORIAL_RADIUS).withHandler(new ContinueOnEvent<EclipseDetector>());
final AttitudesSequence attitudesSequence = new AttitudesSequence();
final AttitudesSequence.SwitchHandler switchHandler = new AttitudesSequence.SwitchHandler() {
public void switchOccurred(AttitudeProvider preceding, AttitudeProvider following, SpacecraftState s) {
if (preceding == dayObservationLaw) {
output.add(s.getDate() + ": switching to night law");
} else {
output.add(s.getDate() + ": switching to day law");
}
}
};
attitudesSequence.addSwitchingCondition(dayObservationLaw, nightRestingLaw, dayNightEvent, false, true, 10.0, AngularDerivativesFilter.USE_R, switchHandler);
attitudesSequence.addSwitchingCondition(nightRestingLaw, dayObservationLaw, nightDayEvent, true, false, 10.0, AngularDerivativesFilter.USE_R, switchHandler);
if (dayNightEvent.g(new SpacecraftState(initialOrbit)) >= 0) {
// initial position is in daytime
attitudesSequence.resetActiveProvider(dayObservationLaw);
} else {
// initial position is in nighttime
attitudesSequence.resetActiveProvider(nightRestingLaw);
}
// Propagator : consider the analytical Eckstein-Hechler model
final Propagator propagator = new EcksteinHechlerPropagator(initialOrbit, attitudesSequence, Constants.EIGEN5C_EARTH_EQUATORIAL_RADIUS, Constants.EIGEN5C_EARTH_MU, Constants.EIGEN5C_EARTH_C20, Constants.EIGEN5C_EARTH_C30, Constants.EIGEN5C_EARTH_C40, Constants.EIGEN5C_EARTH_C50, Constants.EIGEN5C_EARTH_C60);
// Register the switching events to the propagator
attitudesSequence.registerSwitchEvents(propagator);
propagator.setMasterMode(180.0, new OrekitFixedStepHandler() {
public void init(final SpacecraftState s0, final AbsoluteDate t) {
}
public void handleStep(SpacecraftState currentState, boolean isLast) throws OrekitException {
DecimalFormatSymbols angleDegree = new DecimalFormatSymbols(Locale.US);
angleDegree.setDecimalSeparator('\u00b0');
DecimalFormat ad = new DecimalFormat(" 00.000;-00.000", angleDegree);
// the Earth position in spacecraft frame should be along spacecraft Z axis
// during nigthtime and away from it during daytime due to roll and pitch offsets
final Vector3D earth = currentState.toTransform().transformPosition(Vector3D.ZERO);
final double pointingOffset = Vector3D.angle(earth, Vector3D.PLUS_K);
// the g function is the eclipse indicator, its an angle between Sun and Earth limb,
// positive when Sun is outside of Earth limb, negative when Sun is hidden by Earth limb
final double eclipseAngle = dayNightEvent.g(currentState);
output.add(currentState.getDate() + " " + ad.format(FastMath.toDegrees(eclipseAngle)) + " " + ad.format(FastMath.toDegrees(pointingOffset)));
}
});
// Propagate from the initial date for the fixed duration
SpacecraftState finalState = propagator.propagate(initialDate.shiftedBy(12600.));
// to make sure out of orders calls between step handler and event handlers don't mess things up
for (final String line : output) {
System.out.println(line);
}
System.out.println("Propagation ended at " + finalState.getDate());
} catch (OrekitException oe) {
System.err.println(oe.getMessage());
}
}
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