Examples with KeplerianPropagator org.orekit.propagation.analytical.KeplerianPropagator used on opensource projects

Example 46 with KeplerianPropagator

use of org.orekit.propagation.analytical.KeplerianPropagator in project Orekit by CS-SI.

the class AlongTrackAiming method findHalfTrack.

/**
 * Find the ascending or descending part of an orbit track.
 * @param orbit orbit along which tiles should be aligned
 * @param ellipsoid ellipsoid over which track is sampled
 * @param isAscending indicator for zone tiling with respect to ascending
 * or descending orbits
 * @return time stamped ground points on the selected half track
 * @exception OrekitException if some frame conversion fails
 */
private static List<Pair<GeodeticPoint, TimeStampedPVCoordinates>> findHalfTrack(final Orbit orbit, final OneAxisEllipsoid ellipsoid, final boolean isAscending) throws OrekitException {
    // find the span of the next half track
    final Propagator propagator = new KeplerianPropagator(orbit);
    final HalfTrackSpanHandler handler = new HalfTrackSpanHandler(isAscending);
    final LatitudeExtremumDetector detector = new LatitudeExtremumDetector(0.25 * orbit.getKeplerianPeriod(), 1.0e-3, ellipsoid).withHandler(handler).withMaxIter(100);
    propagator.addEventDetector(detector);
    propagator.propagate(orbit.getDate().shiftedBy(3 * orbit.getKeplerianPeriod()));
    // sample the half track
    propagator.clearEventsDetectors();
    final HalfTrackSampler sampler = new HalfTrackSampler(ellipsoid);
    propagator.setMasterMode(handler.getEnd().durationFrom(handler.getStart()) / SAMPLING_STEPS, sampler);
    propagator.propagate(handler.getStart(), handler.getEnd());
    return sampler.getHalfTrack();
}

Example 47 with KeplerianPropagator

use of org.orekit.propagation.analytical.KeplerianPropagator in project Orekit by CS-SI.

the class TargetPointingTest method testNadirTarget.

/**
 * Test with nadir target : Check that when the target is the same as nadir target at date,
 * satellite attitude is the same as nadir attitude at the same date, but different at a different date.
 */
@Test
public void testNadirTarget() throws OrekitException {
    // Elliptic earth shape
    OneAxisEllipsoid earthShape = new OneAxisEllipsoid(6378136.460, 1 / 298.257222101, itrf);
    // Satellite on any position
    CircularOrbit circOrbit = new CircularOrbit(7178000.0, 1.e-5, 0., FastMath.toRadians(50.), 0., FastMath.toRadians(90.), PositionAngle.TRUE, FramesFactory.getEME2000(), date, mu);
    // Target attitude provider with target under satellite nadir
    // *******************************************************
    // Definition of nadir target
    // Create nadir pointing attitude provider
    NadirPointing nadirAttitudeLaw = new NadirPointing(circOrbit.getFrame(), earthShape);
    // Check nadir target
    Vector3D pNadirTarget = nadirAttitudeLaw.getTargetPV(circOrbit, date, itrf).getPosition();
    GeodeticPoint geoNadirTarget = earthShape.transform(pNadirTarget, itrf, date);
    // Create target attitude provider
    TargetPointing targetAttitudeLaw = new TargetPointing(circOrbit.getFrame(), geoNadirTarget, earthShape);
    // 1/ Test that attitudes are the same at date
    // *********************************************
    // i.e the composition of inverse earth pointing rotation
    // with nadir pointing rotation shall be identity.
    // Get satellite rotation from target pointing law at date
    Rotation rotTarget = targetAttitudeLaw.getAttitude(circOrbit, date, circOrbit.getFrame()).getRotation();
    // Get satellite rotation from nadir pointing law at date
    Rotation rotNadir = nadirAttitudeLaw.getAttitude(circOrbit, date, circOrbit.getFrame()).getRotation();
    // Compose attitude rotations
    Rotation rotCompo = rotTarget.composeInverse(rotNadir, RotationConvention.VECTOR_OPERATOR);
    double angle = rotCompo.getAngle();
    Assert.assertEquals(angle, 0.0, Utils.epsilonAngle);
    // 2/ Test that attitudes are different at a different date
    // **********************************************************
    // Extrapolation one minute later
    KeplerianPropagator extrapolator = new KeplerianPropagator(circOrbit);
    // extrapolation duration in seconds
    double delta_t = 60.0;
    AbsoluteDate extrapDate = date.shiftedBy(delta_t);
    Orbit extrapOrbit = extrapolator.propagate(extrapDate).getOrbit();
    // Get satellite rotation from target pointing law at date + 1min
    Rotation extrapRotTarget = targetAttitudeLaw.getAttitude(extrapOrbit, extrapDate, extrapOrbit.getFrame()).getRotation();
    // Get satellite rotation from nadir pointing law at date
    Rotation extrapRotNadir = nadirAttitudeLaw.getAttitude(extrapOrbit, extrapDate, extrapOrbit.getFrame()).getRotation();
    // Compose attitude rotations
    Rotation extrapRotCompo = extrapRotTarget.composeInverse(extrapRotNadir, RotationConvention.VECTOR_OPERATOR);
    double extrapAngle = extrapRotCompo.getAngle();
    Assert.assertEquals(extrapAngle, FastMath.toRadians(24.684793905118823), Utils.epsilonAngle);
}

Example 48 with KeplerianPropagator

use of org.orekit.propagation.analytical.KeplerianPropagator in project Orekit by CS-SI.

the class SolarBodyTest method checkKepler.

private void checkKepler(final PVCoordinatesProvider orbiting, final CelestialBody central, final AbsoluteDate start, final double a, final double epsilon) throws OrekitException {
    // set up Keplerian orbit of orbiting body around central body
    Orbit orbit = new KeplerianOrbit(orbiting.getPVCoordinates(start, central.getInertiallyOrientedFrame()), central.getInertiallyOrientedFrame(), start, central.getGM());
    KeplerianPropagator propagator = new KeplerianPropagator(orbit);
    Assert.assertEquals(a, orbit.getA(), 0.02 * a);
    double duration = FastMath.min(50 * Constants.JULIAN_DAY, 0.01 * orbit.getKeplerianPeriod());
    double max = 0;
    for (AbsoluteDate date = start; date.durationFrom(start) < duration; date = date.shiftedBy(duration / 100)) {
        PVCoordinates ephemPV = orbiting.getPVCoordinates(date, central.getInertiallyOrientedFrame());
        PVCoordinates keplerPV = propagator.propagate(date).getPVCoordinates();
        Vector3D error = keplerPV.getPosition().subtract(ephemPV.getPosition());
        max = FastMath.max(max, error.getNorm());
    }
    Assert.assertTrue(max < epsilon * a);
}

Example 49 with KeplerianPropagator

use of org.orekit.propagation.analytical.KeplerianPropagator in project Orekit by CS-SI.

the class LofOffsetPointingTest method testSpin.

@Test
public void testSpin() throws OrekitException {
    AbsoluteDate date = new AbsoluteDate(new DateComponents(1970, 01, 01), new TimeComponents(3, 25, 45.6789), TimeScalesFactory.getUTC());
    KeplerianOrbit orbit = new KeplerianOrbit(7178000.0, 1.e-4, FastMath.toRadians(50.), FastMath.toRadians(10.), FastMath.toRadians(20.), FastMath.toRadians(30.), PositionAngle.MEAN, FramesFactory.getEME2000(), date, 3.986004415e14);
    final AttitudeProvider law = new LofOffsetPointing(orbit.getFrame(), earthSpheric, new LofOffset(orbit.getFrame(), LOFType.VVLH, RotationOrder.XYX, 0.1, 0.2, 0.3), Vector3D.PLUS_K);
    Propagator propagator = new KeplerianPropagator(orbit, law);
    double h = 0.01;
    SpacecraftState sMinus = propagator.propagate(date.shiftedBy(-h));
    SpacecraftState s0 = propagator.propagate(date);
    SpacecraftState sPlus = propagator.propagate(date.shiftedBy(h));
    // check spin is consistent with attitude evolution
    double errorAngleMinus = Rotation.distance(sMinus.shiftedBy(h).getAttitude().getRotation(), s0.getAttitude().getRotation());
    double evolutionAngleMinus = Rotation.distance(sMinus.getAttitude().getRotation(), s0.getAttitude().getRotation());
    Assert.assertEquals(0.0, errorAngleMinus, 1.0e-6 * evolutionAngleMinus);
    double errorAnglePlus = Rotation.distance(s0.getAttitude().getRotation(), sPlus.shiftedBy(-h).getAttitude().getRotation());
    double evolutionAnglePlus = Rotation.distance(s0.getAttitude().getRotation(), sPlus.getAttitude().getRotation());
    Assert.assertEquals(0.0, errorAnglePlus, 1.0e-6 * evolutionAnglePlus);
    Vector3D spin0 = s0.getAttitude().getSpin();
    Vector3D reference = AngularCoordinates.estimateRate(sMinus.getAttitude().getRotation(), sPlus.getAttitude().getRotation(), 2 * h);
    Assert.assertTrue(spin0.getNorm() > 1.0e-3);
    Assert.assertEquals(0.0, spin0.subtract(reference).getNorm(), 1.0e-10);
}

Example 50 with KeplerianPropagator

use of org.orekit.propagation.analytical.KeplerianPropagator in project Orekit by CS-SI.

the class InertialAttitudeTest method testIsInertial.

@Test
public void testIsInertial() throws OrekitException {
    InertialProvider law = new InertialProvider(new Rotation(new Vector3D(0.6, 0.48, 0.64), 0.9, RotationConvention.VECTOR_OPERATOR));
    KeplerianPropagator propagator = new KeplerianPropagator(orbit0, law);
    Attitude initial = propagator.propagate(t0).getAttitude();
    for (double t = 0; t < 10000.0; t += 100) {
        SpacecraftState state = propagator.propagate(t0.shiftedBy(t));
        checkField(Decimal64Field.getInstance(), law, state.getOrbit(), state.getDate(), state.getFrame());
        Attitude attitude = state.getAttitude();
        Rotation evolution = attitude.getRotation().compose(initial.getRotation().revert(), RotationConvention.VECTOR_OPERATOR);
        Assert.assertEquals(0, evolution.getAngle(), 1.0e-10);
        Assert.assertEquals(FramesFactory.getEME2000(), attitude.getReferenceFrame());
    }
}