Examples with OneAxisEllipsoid org.orekit.bodies.OneAxisEllipsoid used on opensource projects

Example 46 with OneAxisEllipsoid

use of org.orekit.bodies.OneAxisEllipsoid in project Orekit by CS-SI.

the class NadirPointingTest method testSpin.

@Test
public void testSpin() throws OrekitException {
    // Elliptic earth shape
    OneAxisEllipsoid earthShape = new OneAxisEllipsoid(6378136.460, 1 / 298.257222101, itrf);
    // Create earth center pointing attitude provider
    NadirPointing law = new NadirPointing(FramesFactory.getEME2000(), earthShape);
    // Satellite on any position
    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, mu);
    Propagator propagator = new KeplerianPropagator(orbit, law, mu, 2500.0);
    double h = 0.1;
    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, 5.3e-9 * 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, 8.1e-9 * evolutionAnglePlus);
    Vector3D spin0 = s0.getAttitude().getSpin();
    Rotation rM = sMinus.getAttitude().getRotation();
    Rotation rP = sPlus.getAttitude().getRotation();
    Vector3D reference = AngularCoordinates.estimateRate(rM, rP, 2 * h);
    Assert.assertTrue(Rotation.distance(rM, rP) > 2.0e-4);
    Assert.assertEquals(0.0, spin0.subtract(reference).getNorm(), 2.0e-6);
}

Example 47 with OneAxisEllipsoid

use of org.orekit.bodies.OneAxisEllipsoid in project Orekit by CS-SI.

the class NadirPointingTest method testNonSphericEarth.

/**
 * Test in the case of an elliptic earth : nadir pointing shall be :
 *   - the same as earth center pointing in case of equatorial or polar position
 *   - different from earth center pointing in any other case
 */
@Test
public void testNonSphericEarth() throws OrekitException {
    // Elliptic earth shape
    OneAxisEllipsoid earthShape = new OneAxisEllipsoid(6378136.460, 1 / 298.257222101, itrf);
    // Create nadir pointing attitude provider
    NadirPointing nadirAttitudeLaw = new NadirPointing(FramesFactory.getEME2000(), earthShape);
    // Create earth center pointing attitude provider
    BodyCenterPointing earthCenterAttitudeLaw = new BodyCenterPointing(FramesFactory.getEME2000(), earthShape);
    // Satellite on equatorial position
    // **********************************
    KeplerianOrbit kep = new KeplerianOrbit(7178000.0, 1.e-8, FastMath.toRadians(50.), 0., 0., 0., PositionAngle.TRUE, FramesFactory.getEME2000(), date, mu);
    // Get nadir attitude
    Rotation rotNadir = nadirAttitudeLaw.getAttitude(kep, date, kep.getFrame()).getRotation();
    checkField(Decimal64Field.getInstance(), nadirAttitudeLaw, kep, kep.getDate(), kep.getFrame());
    // Get earth center attitude
    Rotation rotCenter = earthCenterAttitudeLaw.getAttitude(kep, date, kep.getFrame()).getRotation();
    // For a satellite at equatorial position, earth center pointing attitude and nadir pointing
    // attitude shall be the same, i.e the composition of inverse earth pointing rotation
    // with nadir pointing rotation shall be identity.
    Rotation rotCompo = rotCenter.composeInverse(rotNadir, RotationConvention.VECTOR_OPERATOR);
    double angle = rotCompo.getAngle();
    Assert.assertEquals(0.0, angle, 5.e-6);
    // Satellite on polar position
    // *****************************
    CircularOrbit circ = new CircularOrbit(7178000.0, 1.e-5, 0., FastMath.toRadians(90.), 0., FastMath.toRadians(90.), PositionAngle.TRUE, FramesFactory.getEME2000(), date, mu);
    // Get nadir attitude
    rotNadir = nadirAttitudeLaw.getAttitude(circ, date, circ.getFrame()).getRotation();
    // Get earth center attitude
    rotCenter = earthCenterAttitudeLaw.getAttitude(circ, date, circ.getFrame()).getRotation();
    // For a satellite at polar position, earth center pointing attitude and nadir pointing
    // attitude shall be the same, i.e the composition of inverse earth pointing rotation
    // with nadir pointing rotation shall be identity.
    rotCompo = rotCenter.composeInverse(rotNadir, RotationConvention.VECTOR_OPERATOR);
    angle = rotCompo.getAngle();
    Assert.assertEquals(angle, 0.0, 5.e-6);
    // Satellite on any position
    // ***************************
    circ = new CircularOrbit(7178000.0, 1.e-5, 0., FastMath.toRadians(50.), 0., FastMath.toRadians(90.), PositionAngle.TRUE, FramesFactory.getEME2000(), date, mu);
    // Get nadir attitude
    rotNadir = nadirAttitudeLaw.getAttitude(circ, date, circ.getFrame()).getRotation();
    // Get earth center attitude
    rotCenter = earthCenterAttitudeLaw.getAttitude(circ, date, circ.getFrame()).getRotation();
    // For a satellite at any position, earth center pointing attitude and nadir pointing
    // and nadir pointing attitude shall not be the same, i.e the composition of inverse earth
    // pointing rotation with nadir pointing rotation shall be different from identity.
    rotCompo = rotCenter.composeInverse(rotNadir, RotationConvention.VECTOR_OPERATOR);
    angle = rotCompo.getAngle();
    Assert.assertEquals(angle, FastMath.toRadians(0.16797386586252272), Utils.epsilonAngle);
}

Example 48 with OneAxisEllipsoid

use of org.orekit.bodies.OneAxisEllipsoid in project Orekit by CS-SI.

the class NadirPointingTest method testVertical.

/**
 * Vertical test : check that Z satellite axis is collinear to local vertical axis,
 *        which direction is : (cos(lon)*cos(lat), sin(lon)*cos(lat), sin(lat)),
 *        where lon et lat stand for observed point coordinates
 *        (i.e satellite ones, since they are the same by construction,
 *        but that's what is to test.
 */
@Test
public void testVertical() throws OrekitException {
    // Elliptic earth shape
    OneAxisEllipsoid earthShape = new OneAxisEllipsoid(6378136.460, 1 / 298.257222101, itrf);
    // Create earth center pointing attitude provider
    NadirPointing nadirAttitudeLaw = new NadirPointing(FramesFactory.getEME2000(), earthShape);
    // Satellite on any position
    CircularOrbit circ = new CircularOrbit(7178000.0, 1.e-5, 0., FastMath.toRadians(50.), 0., FastMath.toRadians(90.), PositionAngle.TRUE, FramesFactory.getEME2000(), date, mu);
    // Vertical test
    // ***************
    // Get observed ground point position/velocity
    TimeStampedPVCoordinates pvTargetItrf = nadirAttitudeLaw.getTargetPV(circ, date, itrf);
    // Convert to geodetic coordinates
    GeodeticPoint geoTarget = earthShape.transform(pvTargetItrf.getPosition(), itrf, date);
    // Compute local vertical axis
    double xVert = FastMath.cos(geoTarget.getLongitude()) * FastMath.cos(geoTarget.getLatitude());
    double yVert = FastMath.sin(geoTarget.getLongitude()) * FastMath.cos(geoTarget.getLatitude());
    double zVert = FastMath.sin(geoTarget.getLatitude());
    Vector3D targetVertical = new Vector3D(xVert, yVert, zVert);
    // Get attitude rotation state
    Rotation rotSatEME2000 = nadirAttitudeLaw.getAttitude(circ, date, circ.getFrame()).getRotation();
    // Get satellite Z axis in EME2000 frame
    Vector3D zSatEME2000 = rotSatEME2000.applyInverseTo(Vector3D.PLUS_K);
    Vector3D zSatItrf = FramesFactory.getEME2000().getTransformTo(itrf, date).transformVector(zSatEME2000);
    // Check that satellite Z axis is collinear to local vertical axis
    double angle = Vector3D.angle(zSatItrf, targetVertical);
    Assert.assertEquals(0.0, FastMath.sin(angle), Utils.epsilonTest);
}

Example 49 with OneAxisEllipsoid

use of org.orekit.bodies.OneAxisEllipsoid in project Orekit by CS-SI.

the class NadirPointingTest method testSlidingDerivatives.

/**
 * Test the derivatives of the sliding target
 */
@Test
public void testSlidingDerivatives() throws OrekitException {
    // Elliptic earth shape
    OneAxisEllipsoid earthShape = new OneAxisEllipsoid(6378136.460, 1 / 298.257222101, itrf);
    // Create earth center pointing attitude provider
    NadirPointing nadirAttitudeLaw = new NadirPointing(FramesFactory.getEME2000(), earthShape);
    // Satellite on any position
    CircularOrbit circ = new CircularOrbit(7178000.0, 1.e-5, 0., FastMath.toRadians(50.), 0., FastMath.toRadians(90.), PositionAngle.TRUE, FramesFactory.getEME2000(), date, mu);
    List<TimeStampedPVCoordinates> sample = new ArrayList<TimeStampedPVCoordinates>();
    for (double dt = -0.1; dt < 0.1; dt += 0.05) {
        Orbit o = circ.shiftedBy(dt);
        sample.add(nadirAttitudeLaw.getTargetPV(o, o.getDate(), o.getFrame()));
    }
    TimeStampedPVCoordinates reference = TimeStampedPVCoordinates.interpolate(circ.getDate(), CartesianDerivativesFilter.USE_P, sample);
    TimeStampedPVCoordinates target = nadirAttitudeLaw.getTargetPV(circ, circ.getDate(), circ.getFrame());
    Assert.assertEquals(0.0, Vector3D.distance(reference.getPosition(), target.getPosition()), 1.0e-15 * reference.getPosition().getNorm());
    Assert.assertEquals(0.0, Vector3D.distance(reference.getVelocity(), target.getVelocity()), 3.0e-11 * reference.getVelocity().getNorm());
    Assert.assertEquals(0.0, Vector3D.distance(reference.getAcceleration(), target.getAcceleration()), 1.3e-5 * reference.getAcceleration().getNorm());
}

Example 50 with OneAxisEllipsoid

use of org.orekit.bodies.OneAxisEllipsoid in project Orekit by CS-SI.

the class BodyCenterPointingTest method doTestSpin.

private <T extends RealFieldElement<T>> void doTestSpin(final Field<T> field) throws OrekitException {
    final double ehMu = 3.9860047e14;
    final double ae = 6.378137e6;
    final double c20 = -1.08263e-3;
    final double c30 = 2.54e-6;
    final double c40 = 1.62e-6;
    final double c50 = 2.3e-7;
    final double c60 = -5.5e-7;
    // Satellite position as circular parameters
    final T zero = field.getZero();
    final T a = zero.add(7178000.0);
    final T e = zero.add(7e-5);
    final T i = zero.add(FastMath.toRadians(50.));
    final T pa = zero.add(FastMath.toRadians(45.));
    final T raan = zero.add(FastMath.toRadians(270.));
    final T m = zero.add(FastMath.toRadians(5.3 - 270));
    // Computation date
    FieldAbsoluteDate<T> date_R = new FieldAbsoluteDate<>(field, new DateComponents(2008, 04, 07), TimeComponents.H00, TimeScalesFactory.getUTC());
    // Orbit
    FieldKeplerianOrbit<T> circ = new FieldKeplerianOrbit<>(a, e, i, pa, raan, m, PositionAngle.MEAN, FramesFactory.getEME2000(), date_R, ehMu);
    // WGS84 Earth model
    OneAxisEllipsoid earth = new OneAxisEllipsoid(Constants.WGS84_EARTH_EQUATORIAL_RADIUS, Constants.WGS84_EARTH_FLATTENING, FramesFactory.getITRF(IERSConventions.IERS_2010, true));
    // Earth center pointing attitude provider
    BodyCenterPointing earthCenterAttitudeLaw = new BodyCenterPointing(circ.getFrame(), earth);
    final FieldAbsoluteDate<T> date = FieldAbsoluteDate.getJ2000Epoch(field).shiftedBy(584.);
    final FieldVector3D<T> position = new FieldVector3D<>(zero.add(3220103.), zero.add(69623.), zero.add(6449822.));
    final FieldVector3D<T> velocity = new FieldVector3D<>(zero.add(6414.7), zero.add(-2006.), zero.add(-3180.));
    final FieldCircularOrbit<T> initialOrbit = new FieldCircularOrbit<>(new FieldPVCoordinates<>(position, velocity), FramesFactory.getEME2000(), date, ehMu);
    FieldEcksteinHechlerPropagator<T> propagator = new FieldEcksteinHechlerPropagator<>(initialOrbit, ae, ehMu, c20, c30, c40, c50, c60);
    propagator.setAttitudeProvider(earthCenterAttitudeLaw);
    double h = 0.01;
    FieldSpacecraftState<T> s0 = propagator.propagate(date);
    FieldSpacecraftState<T> sMinus = propagator.propagate(date.shiftedBy(-h));
    FieldSpacecraftState<T> sPlus = propagator.propagate(date.shiftedBy(h));
    // check spin is consistent with attitude evolution
    T errorAngleMinus = FieldRotation.distance(sMinus.shiftedBy(zero.add(h)).getAttitude().getRotation(), s0.getAttitude().getRotation());
    T evolutionAngleMinus = FieldRotation.distance(sMinus.getAttitude().getRotation(), s0.getAttitude().getRotation());
    Assert.assertEquals(0.0, errorAngleMinus.getReal(), 1.0e-6 * evolutionAngleMinus.getReal());
    T errorAnglePlus = FieldRotation.distance(s0.getAttitude().getRotation(), sPlus.shiftedBy(zero.add(-h)).getAttitude().getRotation());
    T evolutionAnglePlus = FieldRotation.distance(s0.getAttitude().getRotation(), sPlus.getAttitude().getRotation());
    Assert.assertEquals(0.0, errorAnglePlus.getReal(), 1.0e-6 * evolutionAnglePlus.getReal());
    FieldVector3D<T> spin0 = s0.getAttitude().getSpin();
    FieldVector3D<T> reference = FieldAngularCoordinates.estimateRate(sMinus.getAttitude().getRotation(), sPlus.getAttitude().getRotation(), 2 * h);
    Assert.assertTrue(spin0.getNorm().getReal() > 1.0e-3);
    Assert.assertEquals(0.0, spin0.subtract(reference).getNorm().getReal(), 1.0e-13);
}