Examples with ShortPeriodTerms org.orekit.propagation.semianalytical.dsst.forces.ShortPeriodTerms used on opensource projects

Example 1 with ShortPeriodTerms

use of org.orekit.propagation.semianalytical.dsst.forces.ShortPeriodTerms in project Orekit by CS-SI.

the class DSSTPropagator method computeOsculatingOrbit.

/**
 * Compute osculating state from mean state.
 * <p>
 * Compute and add the short periodic variation to the mean {@link SpacecraftState}.
 * </p>
 * @param meanState initial mean state
 * @param shortPeriodTerms short period terms
 * @return osculating state
 * @throws OrekitException if the computation of the short-periodic variation fails
 */
private static EquinoctialOrbit computeOsculatingOrbit(final SpacecraftState meanState, final List<ShortPeriodTerms> shortPeriodTerms) throws OrekitException {
    final double[] mean = new double[6];
    final double[] meanDot = new double[6];
    OrbitType.EQUINOCTIAL.mapOrbitToArray(meanState.getOrbit(), PositionAngle.MEAN, mean, meanDot);
    final double[] y = mean.clone();
    for (final ShortPeriodTerms spt : shortPeriodTerms) {
        final double[] shortPeriodic = spt.value(meanState.getOrbit());
        for (int i = 0; i < shortPeriodic.length; i++) {
            y[i] += shortPeriodic[i];
        }
    }
    return (EquinoctialOrbit) OrbitType.EQUINOCTIAL.mapArrayToOrbit(y, meanDot, PositionAngle.MEAN, meanState.getDate(), meanState.getMu(), meanState.getFrame());
}

Example 2 with ShortPeriodTerms

use of org.orekit.propagation.semianalytical.dsst.forces.ShortPeriodTerms in project Orekit by CS-SI.

the class DSSTPropagator method computeOsculatingState.

/**
 * Conversion from mean to osculating orbit.
 * <p>
 * Compute osculating state <b>in a DSST sense</b>, corresponding to the
 * mean SpacecraftState in input, and according to the Force models taken
 * into account.
 * </p><p>
 * Since the osculating state is obtained by adding short-periodic variation
 * of each force model, the resulting output will depend on the
 * force models parameterized in input.
 * </p>
 * @param mean Mean state to convert
 * @param forces Forces to take into account
 * @param attitudeProvider attitude provider (may be null if there are no Gaussian force models
 * like atmospheric drag, radiation pressure or specific user-defined models)
 * @return osculating state in a DSST sense
 * @throws OrekitException if computation of short periodics fails
 */
public static SpacecraftState computeOsculatingState(final SpacecraftState mean, final AttitudeProvider attitudeProvider, final Collection<DSSTForceModel> forces) throws OrekitException {
    // Create the auxiliary object
    final AuxiliaryElements aux = new AuxiliaryElements(mean.getOrbit(), I);
    // Set the force models
    final List<ShortPeriodTerms> shortPeriodTerms = new ArrayList<ShortPeriodTerms>();
    for (final DSSTForceModel force : forces) {
        force.registerAttitudeProvider(attitudeProvider);
        shortPeriodTerms.addAll(force.initialize(aux, false));
        force.updateShortPeriodTerms(mean);
    }
    final EquinoctialOrbit osculatingOrbit = computeOsculatingOrbit(mean, shortPeriodTerms);
    return new SpacecraftState(osculatingOrbit, mean.getAttitude(), mean.getMass(), mean.getAdditionalStates());
}

Example 3 with ShortPeriodTerms

use of org.orekit.propagation.semianalytical.dsst.forces.ShortPeriodTerms in project Orekit by CS-SI.

the class DSSTPropagator method beforeIntegration.

/**
 * Method called just before integration.
 * <p>
 * The default implementation does nothing, it may be specialized in subclasses.
 * </p>
 * @param initialState initial state
 * @param tEnd target date at which state should be propagated
 * @exception OrekitException if hook cannot be run
 */
@Override
protected void beforeIntegration(final SpacecraftState initialState, final AbsoluteDate tEnd) throws OrekitException {
    // compute common auxiliary elements
    final AuxiliaryElements aux = new AuxiliaryElements(initialState.getOrbit(), I);
    // check if only mean elements must be used
    final boolean meanOnly = isMeanOrbit();
    // initialize all perturbing forces
    final List<ShortPeriodTerms> shortPeriodTerms = new ArrayList<ShortPeriodTerms>();
    for (final DSSTForceModel force : forceModels) {
        shortPeriodTerms.addAll(force.initialize(aux, meanOnly));
    }
    mapper.setShortPeriodTerms(shortPeriodTerms);
    // if required, insert the special short periodics step handler
    if (!meanOnly) {
        final ShortPeriodicsHandler spHandler = new ShortPeriodicsHandler(forceModels);
        final Collection<ODEStepHandler> stepHandlers = new ArrayList<ODEStepHandler>();
        stepHandlers.add(spHandler);
        final ODEIntegrator integrator = getIntegrator();
        final Collection<ODEStepHandler> existing = integrator.getStepHandlers();
        stepHandlers.addAll(existing);
        integrator.clearStepHandlers();
        // add back the existing handlers after the short periodics one
        for (final ODEStepHandler sp : stepHandlers) {
            integrator.addStepHandler(sp);
        }
    }
}

Example 4 with ShortPeriodTerms

use of org.orekit.propagation.semianalytical.dsst.forces.ShortPeriodTerms in project Orekit by CS-SI.

the class DSSTPropagator method computeMeanOrbit.

/**
 * Compute mean state from osculating state.
 * <p>
 * Compute in a DSST sense the mean state corresponding to the input osculating state.
 * </p><p>
 * The computing is done through a fixed-point iteration process.
 * </p>
 * @param osculating initial osculating state
 * @param attitudeProvider attitude provider (may be null if there are no Gaussian force models
 * like atmospheric drag, radiation pressure or specific user-defined models)
 * @param forceModels force models
 * @return mean state
 * @throws OrekitException if the underlying computation of short periodic variation fails
 */
private static Orbit computeMeanOrbit(final SpacecraftState osculating, final AttitudeProvider attitudeProvider, final Collection<DSSTForceModel> forceModels) throws OrekitException {
    // rough initialization of the mean parameters
    EquinoctialOrbit meanOrbit = (EquinoctialOrbit) OrbitType.EQUINOCTIAL.convertType(osculating.getOrbit());
    // threshold for each parameter
    final double epsilon = 1.0e-13;
    final double thresholdA = epsilon * (1 + FastMath.abs(meanOrbit.getA()));
    final double thresholdE = epsilon * (1 + meanOrbit.getE());
    final double thresholdI = epsilon * (1 + meanOrbit.getI());
    final double thresholdL = epsilon * FastMath.PI;
    // ensure all Gaussian force models can rely on attitude
    for (final DSSTForceModel force : forceModels) {
        force.registerAttitudeProvider(attitudeProvider);
    }
    int i = 0;
    while (i++ < 200) {
        final SpacecraftState meanState = new SpacecraftState(meanOrbit, osculating.getAttitude(), osculating.getMass());
        // Create the auxiliary object
        final AuxiliaryElements aux = new AuxiliaryElements(meanOrbit, I);
        // Set the force models
        final List<ShortPeriodTerms> shortPeriodTerms = new ArrayList<ShortPeriodTerms>();
        for (final DSSTForceModel force : forceModels) {
            shortPeriodTerms.addAll(force.initialize(aux, false));
            force.updateShortPeriodTerms(meanState);
        }
        // recompute the osculating parameters from the current mean parameters
        final EquinoctialOrbit rebuilt = computeOsculatingOrbit(meanState, shortPeriodTerms);
        // adapted parameters residuals
        final double deltaA = osculating.getA() - rebuilt.getA();
        final double deltaEx = osculating.getEquinoctialEx() - rebuilt.getEquinoctialEx();
        final double deltaEy = osculating.getEquinoctialEy() - rebuilt.getEquinoctialEy();
        final double deltaHx = osculating.getHx() - rebuilt.getHx();
        final double deltaHy = osculating.getHy() - rebuilt.getHy();
        final double deltaLv = MathUtils.normalizeAngle(osculating.getLv() - rebuilt.getLv(), 0.0);
        // check convergence
        if (FastMath.abs(deltaA) < thresholdA && FastMath.abs(deltaEx) < thresholdE && FastMath.abs(deltaEy) < thresholdE && FastMath.abs(deltaHx) < thresholdI && FastMath.abs(deltaHy) < thresholdI && FastMath.abs(deltaLv) < thresholdL) {
            return meanOrbit;
        }
        // update mean parameters
        meanOrbit = new EquinoctialOrbit(meanOrbit.getA() + deltaA, meanOrbit.getEquinoctialEx() + deltaEx, meanOrbit.getEquinoctialEy() + deltaEy, meanOrbit.getHx() + deltaHx, meanOrbit.getHy() + deltaHy, meanOrbit.getLv() + deltaLv, PositionAngle.TRUE, meanOrbit.getFrame(), meanOrbit.getDate(), meanOrbit.getMu());
    }
    throw new OrekitException(OrekitMessages.UNABLE_TO_COMPUTE_DSST_MEAN_PARAMETERS, i);
}