FieldDSSTPropagator.java
/* Copyright 2002-2020 CS Group
* Licensed to CS Group (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
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package org.orekit.propagation.semianalytical.dsst;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.hipparchus.Field;
import org.hipparchus.RealFieldElement;
import org.hipparchus.ode.FieldODEIntegrator;
import org.hipparchus.ode.FieldODEStateAndDerivative;
import org.hipparchus.ode.sampling.FieldODEStateInterpolator;
import org.hipparchus.ode.sampling.FieldODEStepHandler;
import org.hipparchus.util.FastMath;
import org.hipparchus.util.MathArrays;
import org.hipparchus.util.MathUtils;
import org.orekit.annotation.DefaultDataContext;
import org.orekit.attitudes.AttitudeProvider;
import org.orekit.attitudes.FieldAttitude;
import org.orekit.data.DataContext;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitInternalError;
import org.orekit.errors.OrekitMessages;
import org.orekit.frames.Frame;
import org.orekit.orbits.FieldEquinoctialOrbit;
import org.orekit.orbits.FieldOrbit;
import org.orekit.orbits.OrbitType;
import org.orekit.orbits.PositionAngle;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.propagation.PropagationType;
import org.orekit.propagation.Propagator;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.events.FieldEventDetector;
import org.orekit.propagation.integration.FieldAbstractIntegratedPropagator;
import org.orekit.propagation.integration.FieldStateMapper;
import org.orekit.propagation.numerical.FieldNumericalPropagator;
import org.orekit.propagation.semianalytical.dsst.forces.DSSTForceModel;
import org.orekit.propagation.semianalytical.dsst.forces.DSSTNewtonianAttraction;
import org.orekit.propagation.semianalytical.dsst.forces.FieldShortPeriodTerms;
import org.orekit.propagation.semianalytical.dsst.utilities.FieldAuxiliaryElements;
import org.orekit.propagation.semianalytical.dsst.utilities.FieldFixedNumberInterpolationGrid;
import org.orekit.propagation.semianalytical.dsst.utilities.FieldInterpolationGrid;
import org.orekit.propagation.semianalytical.dsst.utilities.FieldMaxGapInterpolationGrid;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.utils.ParameterDriver;
import org.orekit.utils.ParameterObserver;
/**
* This class propagates {@link org.orekit.orbits.FieldOrbit orbits} using the DSST theory.
* <p>
* Whereas analytical propagators are configured only thanks to their various
* constructors and can be used immediately after construction, such a semianalytical
* propagator configuration involves setting several parameters between construction
* time and propagation time, just as numerical propagators.
* </p>
* <p>
* The configuration parameters that can be set are:
* </p>
* <ul>
* <li>the initial spacecraft state ({@link #setInitialState(FieldSpacecraftState)})</li>
* <li>the various force models ({@link #addForceModel(DSSTForceModel)},
* {@link #removeForceModels()})</li>
* <li>the discrete events that should be triggered during propagation (
* {@link #addEventDetector(org.orekit.propagation.events.FieldEventDetector)},
* {@link #clearEventsDetectors()})</li>
* <li>the binding logic with the rest of the application ({@link #setSlaveMode()},
* {@link #setMasterMode(RealFieldElement, org.orekit.propagation.sampling.FieldOrekitFixedStepHandler)},
* {@link #setMasterMode(org.orekit.propagation.sampling.FieldOrekitStepHandler)},
* {@link #setEphemerisMode()}, {@link #getGeneratedEphemeris()})</li>
* </ul>
* <p>
* From these configuration parameters, only the initial state is mandatory.
* The default propagation settings are in {@link OrbitType#EQUINOCTIAL equinoctial}
* parameters with {@link PositionAngle#TRUE true} longitude argument.
* The central attraction coefficient used to define the initial orbit will be used.
* However, specifying only the initial state would mean the propagator would use
* only Keplerian forces. In this case, the simpler
* {@link org.orekit.propagation.analytical.KeplerianPropagator KeplerianPropagator}
* class would be more effective.
* </p>
* <p>
* The underlying numerical integrator set up in the constructor may also have
* its own configuration parameters. Typical configuration parameters for adaptive
* stepsize integrators are the min, max and perhaps start step size as well as
* the absolute and/or relative errors thresholds.
* </p>
* <p>
* The state that is seen by the integrator is a simple six elements double array.
* These six elements are:
* <ul>
* <li>the {@link org.orekit.orbits.FieldEquinoctialOrbit equinoctial orbit parameters}
* (a, e<sub>x</sub>, e<sub>y</sub>, h<sub>x</sub>, h<sub>y</sub>, λ<sub>m</sub>)
* in meters and radians,</li>
* </ul>
*
* <p>By default, at the end of the propagation, the propagator resets the initial state to the final state,
* thus allowing a new propagation to be started from there without recomputing the part already performed.
* This behaviour can be chenged by calling {@link #setResetAtEnd(boolean)}.
* </p>
* <p>Beware the same instance cannot be used simultaneously by different threads, the class is <em>not</em>
* thread-safe.</p>
*
* @see FieldSpacecraftState
* @see DSSTForceModel
* @author Romain Di Costanzo
* @author Pascal Parraud
* @since 10.0
*/
public class FieldDSSTPropagator<T extends RealFieldElement<T>> extends FieldAbstractIntegratedPropagator<T> {
/** Retrograde factor I.
* <p>
* DSST model needs equinoctial orbit as internal representation.
* Classical equinoctial elements have discontinuities when inclination
* is close to zero. In this representation, I = +1. <br>
* To avoid this discontinuity, another representation exists and equinoctial
* elements can be expressed in a different way, called "retrograde" orbit.
* This implies I = -1. <br>
* As Orekit doesn't implement the retrograde orbit, I is always set to +1.
* But for the sake of consistency with the theory, the retrograde factor
* has been kept in the formulas.
* </p>
*/
private static final int I = 1;
/** Number of grid points per integration step to be used in interpolation of short periodics coefficients.*/
private static final int INTERPOLATION_POINTS_PER_STEP = 3;
/** Default value for epsilon. */
private static final double EPSILON_DEFAULT = 1.0e-13;
/** Default value for maxIterations. */
private static final int MAX_ITERATIONS_DEFAULT = 200;
/** Flag specifying whether the initial orbital state is given with osculating elements. */
private boolean initialIsOsculating;
/** Field used by this class.*/
private final Field<T> field;
/** Force models used to compute short periodic terms. */
private final transient List<DSSTForceModel> forceModels;
/** State mapper holding the force models. */
private FieldMeanPlusShortPeriodicMapper mapper;
/** Generator for the interpolation grid. */
private FieldInterpolationGrid<T> interpolationgrid;
/** Create a new instance of DSSTPropagator.
* <p>
* After creation, there are no perturbing forces at all.
* This means that if {@link #addForceModel addForceModel}
* is not called after creation, the integrated orbit will
* follow a Keplerian evolution only.
* </p>
*
* <p>This constructor uses the {@link DataContext#getDefault() default data context}.
*
* @param field field used by default
* @param integrator numerical integrator to use for propagation.
* @param propagationType type of orbit to output (mean or osculating).
* @see #FieldDSSTPropagator(Field, FieldODEIntegrator, PropagationType,
* AttitudeProvider)
*/
@DefaultDataContext
public FieldDSSTPropagator(final Field<T> field, final FieldODEIntegrator<T> integrator, final PropagationType propagationType) {
this(field, integrator, propagationType,
Propagator.getDefaultLaw(DataContext.getDefault().getFrames()));
}
/** Create a new instance of DSSTPropagator.
* <p>
* After creation, there are no perturbing forces at all.
* This means that if {@link #addForceModel addForceModel}
* is not called after creation, the integrated orbit will
* follow a Keplerian evolution only.
* </p>
* @param field field used by default
* @param integrator numerical integrator to use for propagation.
* @param propagationType type of orbit to output (mean or osculating).
* @param attitudeProvider attitude law to use.
* @since 10.1
*/
public FieldDSSTPropagator(final Field<T> field,
final FieldODEIntegrator<T> integrator,
final PropagationType propagationType,
final AttitudeProvider attitudeProvider) {
super(field, integrator, propagationType);
this.field = field;
forceModels = new ArrayList<DSSTForceModel>();
initMapper(field);
// DSST uses only equinoctial orbits and mean longitude argument
setOrbitType(OrbitType.EQUINOCTIAL);
setPositionAngleType(PositionAngle.MEAN);
setAttitudeProvider(attitudeProvider);
setInterpolationGridToFixedNumberOfPoints(INTERPOLATION_POINTS_PER_STEP);
}
/** Create a new instance of DSSTPropagator.
* <p>
* After creation, there are no perturbing forces at all.
* This means that if {@link #addForceModel addForceModel}
* is not called after creation, the integrated orbit will
* follow a Keplerian evolution only. Only the mean orbits
* will be generated.
* </p>
*
* <p>This constructor uses the {@link DataContext#getDefault() default data context}.
*
* @param field fied used by default
* @param integrator numerical integrator to use for propagation.
* @see #FieldDSSTPropagator(Field, FieldODEIntegrator, AttitudeProvider)
*/
@DefaultDataContext
public FieldDSSTPropagator(final Field<T> field, final FieldODEIntegrator<T> integrator) {
this(field, integrator,
Propagator.getDefaultLaw(DataContext.getDefault().getFrames()));
}
/** Create a new instance of DSSTPropagator.
* <p>
* After creation, there are no perturbing forces at all.
* This means that if {@link #addForceModel addForceModel}
* is not called after creation, the integrated orbit will
* follow a Keplerian evolution only. Only the mean orbits
* will be generated.
* </p>
* @param field fied used by default
* @param integrator numerical integrator to use for propagation.
* @param attitudeProvider attitude law to use.
* @since 10.1
*/
public FieldDSSTPropagator(final Field<T> field,
final FieldODEIntegrator<T> integrator,
final AttitudeProvider attitudeProvider) {
super(field, integrator, PropagationType.MEAN);
this.field = field;
forceModels = new ArrayList<DSSTForceModel>();
initMapper(field);
// DSST uses only equinoctial orbits and mean longitude argument
setOrbitType(OrbitType.EQUINOCTIAL);
setPositionAngleType(PositionAngle.MEAN);
setAttitudeProvider(attitudeProvider);
setInterpolationGridToFixedNumberOfPoints(INTERPOLATION_POINTS_PER_STEP);
}
/** Set the central attraction coefficient μ.
* <p>
* Setting the central attraction coefficient is
* equivalent to {@link #addForceModel(DSSTForceModel) add}
* a {@link DSSTNewtonianAttraction} force model.
* </p>
* @param mu central attraction coefficient (m³/s²)
* @see #addForceModel(DSSTForceModel)
* @see #getAllForceModels()
*/
public void setMu(final T mu) {
addForceModel(new DSSTNewtonianAttraction(mu.getReal()));
}
/** Set the central attraction coefficient μ only in upper class.
* @param mu central attraction coefficient (m³/s²)
*/
private void superSetMu(final T mu) {
super.setMu(mu);
}
/** Check if Newtonian attraction force model is available.
* <p>
* Newtonian attraction is always the last force model in the list.
* </p>
* @return true if Newtonian attraction force model is available
*/
private boolean hasNewtonianAttraction() {
final int last = forceModels.size() - 1;
return last >= 0 && forceModels.get(last) instanceof DSSTNewtonianAttraction;
}
/** Set the initial state with osculating orbital elements.
* @param initialState initial state (defined with osculating elements)
*/
public void setInitialState(final FieldSpacecraftState<T> initialState) {
setInitialState(initialState, PropagationType.OSCULATING);
}
/** Set the initial state.
* @param initialState initial state
* @param stateType defined if the orbital state is defined with osculating or mean elements
*/
public void setInitialState(final FieldSpacecraftState<T> initialState,
final PropagationType stateType) {
switch (stateType) {
case MEAN:
initialIsOsculating = false;
break;
case OSCULATING:
initialIsOsculating = true;
break;
default:
throw new OrekitInternalError(null);
}
resetInitialState(initialState);
}
/** Reset the initial state.
*
* @param state new initial state
*/
@Override
public void resetInitialState(final FieldSpacecraftState<T> state) {
super.resetInitialState(state);
if (!hasNewtonianAttraction()) {
// use the state to define central attraction
setMu(state.getMu());
}
super.setStartDate(state.getDate());
}
/** Set the selected short periodic coefficients that must be stored as additional states.
* @param selectedCoefficients short periodic coefficients that must be stored as additional states
* (null means no coefficients are selected, empty set means all coefficients are selected)
*/
public void setSelectedCoefficients(final Set<String> selectedCoefficients) {
mapper.setSelectedCoefficients(selectedCoefficients == null ?
null : new HashSet<String>(selectedCoefficients));
}
/** Get the selected short periodic coefficients that must be stored as additional states.
* @return short periodic coefficients that must be stored as additional states
* (null means no coefficients are selected, empty set means all coefficients are selected)
*/
public Set<String> getSelectedCoefficients() {
final Set<String> set = mapper.getSelectedCoefficients();
return set == null ? null : Collections.unmodifiableSet(set);
}
/** Check if the initial state is provided in osculating elements.
* @return true if initial state is provided in osculating elements
*/
public boolean initialIsOsculating() {
return initialIsOsculating;
}
/** Set the interpolation grid generator.
* <p>
* The generator will create an interpolation grid with a fixed
* number of points for each mean element integration step.
* </p>
* <p>
* If neither {@link #setInterpolationGridToFixedNumberOfPoints(int)}
* nor {@link #setInterpolationGridToMaxTimeGap(RealFieldElement)} has been called,
* by default the propagator is set as to 3 interpolations points per step.
* </p>
* @param interpolationPoints number of interpolation points at
* each integration step
* @see #setInterpolationGridToMaxTimeGap(RealFieldElement)
* @since 7.1
*/
public void setInterpolationGridToFixedNumberOfPoints(final int interpolationPoints) {
interpolationgrid = new FieldFixedNumberInterpolationGrid<>(field, interpolationPoints);
}
/** Set the interpolation grid generator.
* <p>
* The generator will create an interpolation grid with a maximum
* time gap between interpolation points.
* </p>
* <p>
* If neither {@link #setInterpolationGridToFixedNumberOfPoints(int)}
* nor {@link #setInterpolationGridToMaxTimeGap(RealFieldElement)} has been called,
* by default the propagator is set as to 3 interpolations points per step.
* </p>
* @param maxGap maximum time gap between interpolation points (seconds)
* @see #setInterpolationGridToFixedNumberOfPoints(int)
* @since 7.1
*/
public void setInterpolationGridToMaxTimeGap(final T maxGap) {
interpolationgrid = new FieldMaxGapInterpolationGrid<>(field, maxGap);
}
/** Add a force model to the global perturbation model.
* <p>
* If this method is not called at all,
* the integrated orbit will follow a Keplerian evolution only.
* </p>
* @param force perturbing {@link DSSTForceModel force} to add
* @see #removeForceModels()
* @see #setMu(RealFieldElement)
*/
public void addForceModel(final DSSTForceModel force) {
if (force instanceof DSSTNewtonianAttraction) {
// we want to add the central attraction force model
try {
// ensure we are notified of any mu change
force.getParametersDrivers()[0].addObserver(new ParameterObserver() {
/** {@inheritDoc} */
@Override
public void valueChanged(final double previousValue, final ParameterDriver driver) {
superSetMu(field.getZero().add(driver.getValue()));
}
});
} catch (OrekitException oe) {
// this should never happen
throw new OrekitInternalError(oe);
}
if (hasNewtonianAttraction()) {
// there is already a central attraction model, replace it
forceModels.set(forceModels.size() - 1, force);
} else {
// there are no central attraction model yet, add it at the end of the list
forceModels.add(force);
}
} else {
// we want to add a perturbing force model
if (hasNewtonianAttraction()) {
// insert the new force model before Newtonian attraction,
// which should always be the last one in the list
forceModels.add(forceModels.size() - 1, force);
} else {
// we only have perturbing force models up to now, just append at the end of the list
forceModels.add(force);
}
}
force.registerAttitudeProvider(getAttitudeProvider());
}
/** Remove all perturbing force models from the global perturbation model
* (except central attraction).
* <p>
* Once all perturbing forces have been removed (and as long as no new force model is added),
* the integrated orbit will follow a Keplerian evolution only.
* </p>
* @see #addForceModel(DSSTForceModel)
*/
public void removeForceModels() {
final int last = forceModels.size() - 1;
if (hasNewtonianAttraction()) {
// preserve the Newtonian attraction model at the end
final DSSTForceModel newton = forceModels.get(last);
forceModels.clear();
forceModels.add(newton);
} else {
forceModels.clear();
}
}
/** Get all the force models, perturbing forces and Newtonian attraction included.
* @return list of perturbing force models, with Newtonian attraction being the
* last one
* @see #addForceModel(DSSTForceModel)
* @see #setMu(RealFieldElement)
*/
public List<DSSTForceModel> getAllForceModels() {
return Collections.unmodifiableList(forceModels);
}
/** Get propagation parameter type.
* @return orbit type used for propagation
*/
public OrbitType getOrbitType() {
return super.getOrbitType();
}
/** Get propagation parameter type.
* @return angle type to use for propagation
*/
public PositionAngle getPositionAngleType() {
return super.getPositionAngleType();
}
/** 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
*/
@SuppressWarnings("unchecked")
public FieldSpacecraftState<T> computeOsculatingState(final FieldSpacecraftState<T> mean,
final AttitudeProvider attitudeProvider,
final Collection<DSSTForceModel> forces) {
//Create the auxiliary object
final FieldAuxiliaryElements<T> aux = new FieldAuxiliaryElements<>(mean.getOrbit(), I);
// Set the force models
final List<FieldShortPeriodTerms<T>> shortPeriodTerms = new ArrayList<FieldShortPeriodTerms<T>>();
for (final DSSTForceModel force : forces) {
force.registerAttitudeProvider(attitudeProvider);
shortPeriodTerms.addAll(force.initialize(aux, PropagationType.OSCULATING, force.getParameters(field)));
force.updateShortPeriodTerms(force.getParameters(field), mean);
}
final FieldEquinoctialOrbit<T> osculatingOrbit = computeOsculatingOrbit(mean, shortPeriodTerms);
return new FieldSpacecraftState<>(osculatingOrbit, mean.getAttitude(), mean.getMass(),
mean.getAdditionalStates());
}
/** Conversion from osculating to mean orbit.
* <p>
* Compute mean state <b>in a DSST sense</b>, corresponding to the
* osculating SpacecraftState in input, and according to the Force models
* taken into account.
* </p><p>
* Since the osculating state is obtained with the computation of
* short-periodic variation of each force model, the resulting output will
* depend on the force models parameterized in input.
* </p><p>
* The computation is done through a fixed-point iteration process.
* </p>
* @param osculating Osculating state to convert
* @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 forceModel Forces to take into account
* @return mean state in a DSST sense
*/
public FieldSpacecraftState<T> computeMeanState(final FieldSpacecraftState<T> osculating,
final AttitudeProvider attitudeProvider,
final Collection<DSSTForceModel> forceModel) {
return computeMeanState(osculating, attitudeProvider, forceModel, EPSILON_DEFAULT, MAX_ITERATIONS_DEFAULT);
}
/** Conversion from osculating to mean orbit.
* <p>
* Compute mean state <b>in a DSST sense</b>, corresponding to the
* osculating SpacecraftState in input, and according to the Force models
* taken into account.
* </p><p>
* Since the osculating state is obtained with the computation of
* short-periodic variation of each force model, the resulting output will
* depend on the force models parameterized in input.
* </p><p>
* The computation is done through a fixed-point iteration process.
* </p>
* @param osculating Osculating state to convert
* @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 forceModel Forces to take into account
* @param epsilon convergence threshold for mean parameters conversion
* @param maxIterations maximum iterations for mean parameters conversion
* @return mean state in a DSST sense
* @since 10.1
*/
public FieldSpacecraftState<T> computeMeanState(final FieldSpacecraftState<T> osculating,
final AttitudeProvider attitudeProvider,
final Collection<DSSTForceModel> forceModel,
final double epsilon,
final int maxIterations) {
final FieldOrbit<T> meanOrbit = computeMeanOrbit(osculating, attitudeProvider, forceModel, epsilon, maxIterations);
return new FieldSpacecraftState<>(meanOrbit, osculating.getAttitude(), osculating.getMass(), osculating.getAdditionalStates());
}
/** Override the default value of the parameter.
* <p>
* By default, if the initial orbit is defined as osculating,
* it will be averaged over 2 satellite revolutions.
* This can be changed by using this method.
* </p>
* @param satelliteRevolution number of satellite revolutions to use for converting osculating to mean
* elements
*/
public void setSatelliteRevolution(final int satelliteRevolution) {
mapper.setSatelliteRevolution(satelliteRevolution);
}
/** Get the number of satellite revolutions to use for converting osculating to mean elements.
* @return number of satellite revolutions to use for converting osculating to mean elements
*/
public int getSatelliteRevolution() {
return mapper.getSatelliteRevolution();
}
/** {@inheritDoc} */
@Override
public void setAttitudeProvider(final AttitudeProvider attitudeProvider) {
super.setAttitudeProvider(attitudeProvider);
//Register the attitude provider for each force model
for (final DSSTForceModel force : forceModels) {
force.registerAttitudeProvider(attitudeProvider);
}
}
/** 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
*/
@Override
protected void beforeIntegration(final FieldSpacecraftState<T> initialState,
final FieldAbsoluteDate<T> tEnd) {
// check if only mean elements must be used
final PropagationType type = isMeanOrbit();
// compute common auxiliary elements
final FieldAuxiliaryElements<T> aux = new FieldAuxiliaryElements<>(initialState.getOrbit(), I);
// initialize all perturbing forces
final List<FieldShortPeriodTerms<T>> shortPeriodTerms = new ArrayList<FieldShortPeriodTerms<T>>();
for (final DSSTForceModel force : forceModels) {
shortPeriodTerms.addAll(force.initialize(aux, type, force.getParameters(field)));
}
mapper.setShortPeriodTerms(shortPeriodTerms);
// if required, insert the special short periodics step handler
if (type == PropagationType.OSCULATING) {
final FieldShortPeriodicsHandler spHandler = new FieldShortPeriodicsHandler(forceModels);
final Collection<FieldODEStepHandler<T>> stepHandlers = new ArrayList<FieldODEStepHandler<T>>();
stepHandlers.add(spHandler);
final FieldODEIntegrator<T> integrator = getIntegrator();
final Collection<FieldODEStepHandler<T>> existing = integrator.getStepHandlers();
stepHandlers.addAll(existing);
integrator.clearStepHandlers();
// add back the existing handlers after the short periodics one
for (final FieldODEStepHandler<T> sp : stepHandlers) {
integrator.addStepHandler(sp);
}
}
}
/** {@inheritDoc} */
@Override
protected void afterIntegration() {
// remove the special short periodics step handler if added before
if (isMeanOrbit() == PropagationType.OSCULATING) {
final List<FieldODEStepHandler<T>> preserved = new ArrayList<FieldODEStepHandler<T>>();
final FieldODEIntegrator<T> integrator = getIntegrator();
// clear the list
integrator.clearStepHandlers();
// add back the step handlers that were important for the user
for (final FieldODEStepHandler<T> sp : preserved) {
integrator.addStepHandler(sp);
}
}
}
/** 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 forceModel force models
* @param epsilon convergence threshold for mean parameters conversion
* @param maxIterations maximum iterations for mean parameters conversion
* @return mean state
* @since 10.1
*/
@SuppressWarnings("unchecked")
private FieldOrbit<T> computeMeanOrbit(final FieldSpacecraftState<T> osculating, final AttitudeProvider attitudeProvider, final Collection<DSSTForceModel> forceModel,
final double epsilon, final int maxIterations) {
// zero
final T zero = field.getZero();
// rough initialization of the mean parameters
FieldEquinoctialOrbit<T> meanOrbit = (FieldEquinoctialOrbit<T>) OrbitType.EQUINOCTIAL.convertType(osculating.getOrbit());
// threshold for each parameter
final T epsilonT = zero.add(epsilon);
final T thresholdA = epsilonT.multiply(FastMath.abs(meanOrbit.getA()).add(1.));
final T thresholdE = epsilonT.multiply(meanOrbit.getE().add(1.));
final T thresholdI = epsilonT.multiply(meanOrbit.getI().add(1.));
final T thresholdL = epsilonT.multiply(FastMath.PI);
// ensure all Gaussian force models can rely on attitude
for (final DSSTForceModel force : forceModel) {
force.registerAttitudeProvider(attitudeProvider);
}
int i = 0;
while (i++ < maxIterations) {
final FieldSpacecraftState<T> meanState = new FieldSpacecraftState<>(meanOrbit, osculating.getAttitude(), osculating.getMass());
//Create the auxiliary object
final FieldAuxiliaryElements<T> aux = new FieldAuxiliaryElements<>(meanOrbit, I);
// Set the force models
final List<FieldShortPeriodTerms<T>> shortPeriodTerms = new ArrayList<FieldShortPeriodTerms<T>>();
for (final DSSTForceModel force : forceModel) {
shortPeriodTerms.addAll(force.initialize(aux, PropagationType.OSCULATING, force.getParameters(field)));
force.updateShortPeriodTerms(force.getParameters(field), meanState);
}
// recompute the osculating parameters from the current mean parameters
final FieldEquinoctialOrbit<T> rebuilt = computeOsculatingOrbit(meanState, shortPeriodTerms);
// adapted parameters residuals
final T deltaA = osculating.getA().subtract(rebuilt.getA());
final T deltaEx = osculating.getEquinoctialEx().subtract(rebuilt.getEquinoctialEx());
final T deltaEy = osculating.getEquinoctialEy().subtract(rebuilt.getEquinoctialEy());
final T deltaHx = osculating.getHx().subtract(rebuilt.getHx());
final T deltaHy = osculating.getHy().subtract(rebuilt.getHy());
final T deltaLv = MathUtils.normalizeAngle(osculating.getLv().subtract(rebuilt.getLv()), zero);
// check convergence
if (FastMath.abs(deltaA).getReal() < thresholdA.getReal() &&
FastMath.abs(deltaEx).getReal() < thresholdE.getReal() &&
FastMath.abs(deltaEy).getReal() < thresholdE.getReal() &&
FastMath.abs(deltaHx).getReal() < thresholdI.getReal() &&
FastMath.abs(deltaHy).getReal() < thresholdI.getReal() &&
FastMath.abs(deltaLv).getReal() < thresholdL.getReal()) {
return meanOrbit;
}
// update mean parameters
meanOrbit = new FieldEquinoctialOrbit<>(meanOrbit.getA().add(deltaA),
meanOrbit.getEquinoctialEx().add(deltaEx),
meanOrbit.getEquinoctialEy().add(deltaEy),
meanOrbit.getHx().add(deltaHx),
meanOrbit.getHy().add(deltaHy),
meanOrbit.getLv().add(deltaLv),
PositionAngle.TRUE, meanOrbit.getFrame(),
meanOrbit.getDate(), meanOrbit.getMu());
}
throw new OrekitException(OrekitMessages.UNABLE_TO_COMPUTE_DSST_MEAN_PARAMETERS, i);
}
/** 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
*/
private FieldEquinoctialOrbit<T> computeOsculatingOrbit(final FieldSpacecraftState<T> meanState,
final List<FieldShortPeriodTerms<T>> shortPeriodTerms) {
final T[] mean = MathArrays.buildArray(field, 6);
final T[] meanDot = MathArrays.buildArray(field, 6);
OrbitType.EQUINOCTIAL.mapOrbitToArray(meanState.getOrbit(), PositionAngle.MEAN, mean, meanDot);
final T[] y = mean.clone();
for (final FieldShortPeriodTerms<T> spt : shortPeriodTerms) {
final T[] shortPeriodic = spt.value(meanState.getOrbit());
for (int i = 0; i < shortPeriodic.length; i++) {
y[i] = y[i].add(shortPeriodic[i]);
}
}
return (FieldEquinoctialOrbit<T>) OrbitType.EQUINOCTIAL.mapArrayToOrbit(y, meanDot,
PositionAngle.MEAN, meanState.getDate(),
meanState.getMu(), meanState.getFrame());
}
/** {@inheritDoc} */
@Override
protected FieldSpacecraftState<T> getInitialIntegrationState() {
if (initialIsOsculating) {
// the initial state is an osculating state,
// it must be converted to mean state
return computeMeanState(getInitialState(), getAttitudeProvider(), forceModels);
} else {
// the initial state is already a mean state
return getInitialState();
}
}
/** {@inheritDoc}
* <p>
* Note that for DSST, orbit type is hardcoded to {@link OrbitType#EQUINOCTIAL}
* and position angle type is hardcoded to {@link PositionAngle#MEAN}, so
* the corresponding parameters are ignored.
* </p>
*/
@Override
protected FieldStateMapper<T> createMapper(final FieldAbsoluteDate<T> referenceDate, final T mu,
final OrbitType ignoredOrbitType, final PositionAngle ignoredPositionAngleType,
final AttitudeProvider attitudeProvider, final Frame frame) {
// create a mapper with the common settings provided as arguments
final FieldMeanPlusShortPeriodicMapper newMapper =
new FieldMeanPlusShortPeriodicMapper(referenceDate, mu, attitudeProvider, frame);
// copy the specific settings from the existing mapper
if (mapper != null) {
newMapper.setSatelliteRevolution(mapper.getSatelliteRevolution());
newMapper.setSelectedCoefficients(mapper.getSelectedCoefficients());
newMapper.setShortPeriodTerms(mapper.getShortPeriodTerms());
}
mapper = newMapper;
return mapper;
}
/** Internal mapper using mean parameters plus short periodic terms. */
private class FieldMeanPlusShortPeriodicMapper extends FieldStateMapper<T> {
/** Short periodic coefficients that must be stored as additional states. */
private Set<String> selectedCoefficients;
/** Number of satellite revolutions in the averaging interval. */
private int satelliteRevolution;
/** Short period terms. */
private List<FieldShortPeriodTerms<T>> shortPeriodTerms;
/** Simple constructor.
* @param referenceDate reference date
* @param mu central attraction coefficient (m³/s²)
* @param attitudeProvider attitude provider
* @param frame inertial frame
*/
FieldMeanPlusShortPeriodicMapper(final FieldAbsoluteDate<T> referenceDate, final T mu,
final AttitudeProvider attitudeProvider, final Frame frame) {
super(referenceDate, mu, OrbitType.EQUINOCTIAL, PositionAngle.MEAN, attitudeProvider, frame);
this.selectedCoefficients = null;
// Default averaging period for conversion from osculating to mean elements
this.satelliteRevolution = 2;
this.shortPeriodTerms = Collections.emptyList();
}
/** {@inheritDoc} */
@Override
public FieldSpacecraftState<T> mapArrayToState(final FieldAbsoluteDate<T> date,
final T[] y, final T[] yDot,
final PropagationType type) {
// add short periodic variations to mean elements to get osculating elements
// (the loop may not be performed if there are no force models and in the
// case we want to remain in mean parameters only)
final T[] elements = y.clone();
final Map<String, T[]> coefficients;
switch (type) {
case MEAN:
coefficients = null;
break;
case OSCULATING:
final FieldOrbit<T> meanOrbit = OrbitType.EQUINOCTIAL.mapArrayToOrbit(elements, yDot, PositionAngle.MEAN, date, getMu(), getFrame());
coefficients = selectedCoefficients == null ? null : new HashMap<String, T[]>();
for (final FieldShortPeriodTerms<T> spt : shortPeriodTerms) {
final T[] shortPeriodic = spt.value(meanOrbit);
for (int i = 0; i < shortPeriodic.length; i++) {
elements[i] = elements[i].add(shortPeriodic[i]);
}
if (selectedCoefficients != null) {
coefficients.putAll(spt.getCoefficients(date, selectedCoefficients));
}
}
break;
default:
throw new OrekitInternalError(null);
}
final T mass = elements[6];
if (mass.getReal() <= 0.0) {
throw new OrekitException(OrekitMessages.SPACECRAFT_MASS_BECOMES_NEGATIVE, mass);
}
final FieldOrbit<T> orbit = OrbitType.EQUINOCTIAL.mapArrayToOrbit(elements, yDot, PositionAngle.MEAN, date, getMu(), getFrame());
final FieldAttitude<T> attitude = getAttitudeProvider().getAttitude(orbit, date, getFrame());
if (coefficients == null) {
return new FieldSpacecraftState<>(orbit, attitude, mass);
} else {
return new FieldSpacecraftState<>(orbit, attitude, mass, coefficients);
}
}
/** {@inheritDoc} */
@Override
public void mapStateToArray(final FieldSpacecraftState<T> state, final T[] y, final T[] yDot) {
OrbitType.EQUINOCTIAL.mapOrbitToArray(state.getOrbit(), PositionAngle.MEAN, y, yDot);
y[6] = state.getMass();
}
/** Set the number of satellite revolutions to use for converting osculating to mean elements.
* <p>
* By default, if the initial orbit is defined as osculating,
* it will be averaged over 2 satellite revolutions.
* This can be changed by using this method.
* </p>
* @param satelliteRevolution number of satellite revolutions to use for converting osculating to mean
* elements
*/
public void setSatelliteRevolution(final int satelliteRevolution) {
this.satelliteRevolution = satelliteRevolution;
}
/** Get the number of satellite revolutions to use for converting osculating to mean elements.
* @return number of satellite revolutions to use for converting osculating to mean elements
*/
public int getSatelliteRevolution() {
return satelliteRevolution;
}
/** Set the selected short periodic coefficients that must be stored as additional states.
* @param selectedCoefficients short periodic coefficients that must be stored as additional states
* (null means no coefficients are selected, empty set means all coefficients are selected)
*/
public void setSelectedCoefficients(final Set<String> selectedCoefficients) {
this.selectedCoefficients = selectedCoefficients;
}
/** Get the selected short periodic coefficients that must be stored as additional states.
* @return short periodic coefficients that must be stored as additional states
* (null means no coefficients are selected, empty set means all coefficients are selected)
*/
public Set<String> getSelectedCoefficients() {
return selectedCoefficients;
}
/** Set the short period terms.
* @param shortPeriodTerms short period terms
* @since 7.1
*/
public void setShortPeriodTerms(final List<FieldShortPeriodTerms<T>> shortPeriodTerms) {
this.shortPeriodTerms = shortPeriodTerms;
}
/** Get the short period terms.
* @return shortPeriodTerms short period terms
* @since 7.1
*/
public List<FieldShortPeriodTerms<T>> getShortPeriodTerms() {
return shortPeriodTerms;
}
}
/** {@inheritDoc} */
@Override
protected MainStateEquations<T> getMainStateEquations(final FieldODEIntegrator<T> integrator) {
return new Main(integrator);
}
/** Internal class for mean parameters integration. */
private class Main implements MainStateEquations<T> {
/** Derivatives array. */
private final T[] yDot;
/** Simple constructor.
* @param integrator numerical integrator to use for propagation.
*/
Main(final FieldODEIntegrator<T> integrator) {
yDot = MathArrays.buildArray(field, 7);
for (final DSSTForceModel forceModel : forceModels) {
final FieldEventDetector<T>[] modelDetectors = forceModel.getFieldEventsDetectors(field);
if (modelDetectors != null) {
for (final FieldEventDetector<T> detector : modelDetectors) {
setUpEventDetector(integrator, detector);
}
}
}
}
/** {@inheritDoc} */
@Override
public void init(final FieldSpacecraftState<T> initialState, final FieldAbsoluteDate<T> target) {
}
/** {@inheritDoc} */
@Override
public T[] computeDerivatives(final FieldSpacecraftState<T> state) {
final T zero = state.getDate().getField().getZero();
Arrays.fill(yDot, zero);
// compute common auxiliary elements
final FieldAuxiliaryElements<T> auxiliaryElements = new FieldAuxiliaryElements<>(state.getOrbit(), I);
// compute the contributions of all perturbing forces
for (final DSSTForceModel forceModel : forceModels) {
final T[] daidt = elementRates(forceModel, state, auxiliaryElements, forceModel.getParameters(field));
for (int i = 0; i < daidt.length; i++) {
yDot[i] = yDot[i].add(daidt[i]);
}
}
return yDot.clone();
}
/** This method allows to compute the mean equinoctial elements rates da<sub>i</sub> / dt
* for a specific force model.
* @param forceModel force to take into account
* @param state current state
* @param auxiliaryElements auxiliary elements related to the current orbit
* @param parameters force model parameters
* @return the mean equinoctial elements rates da<sub>i</sub> / dt
*/
private T[] elementRates(final DSSTForceModel forceModel,
final FieldSpacecraftState<T> state,
final FieldAuxiliaryElements<T> auxiliaryElements,
final T[] parameters) {
return forceModel.getMeanElementRate(state, auxiliaryElements, parameters);
}
}
/** Estimate tolerance vectors for an AdaptativeStepsizeIntegrator.
* <p>
* The errors are estimated from partial derivatives properties of orbits,
* starting from a scalar position error specified by the user.
* Considering the energy conservation equation V = sqrt(mu (2/r - 1/a)),
* we get at constant energy (i.e. on a Keplerian trajectory):
*
* <pre>
* V² r |dV| = mu |dr|
* </pre>
*
* <p> So we deduce a scalar velocity error consistent with the position error. From here, we apply
* orbits Jacobians matrices to get consistent errors on orbital parameters.
*
* <p>
* The tolerances are only <em>orders of magnitude</em>, and integrator tolerances are only
* local estimates, not global ones. So some care must be taken when using these tolerances.
* Setting 1mm as a position error does NOT mean the tolerances will guarantee a 1mm error
* position after several orbits integration.
* </p>
* @param <T> elements type
* @param dP user specified position error (m)
* @param orbit reference orbit
* @return a two rows array, row 0 being the absolute tolerance error
* and row 1 being the relative tolerance error
*/
public static <T extends RealFieldElement<T>> double[][] tolerances(final T dP, final FieldOrbit<T> orbit) {
return FieldNumericalPropagator.tolerances(dP, orbit, OrbitType.EQUINOCTIAL);
}
/** Step handler used to compute the parameters for the short periodic contributions.
* @author Lucian Barbulescu
*/
private class FieldShortPeriodicsHandler implements FieldODEStepHandler<T> {
/** Force models used to compute short periodic terms. */
private final List<DSSTForceModel> forceModels;
/** Constructor.
* @param forceModels force models
*/
FieldShortPeriodicsHandler(final List<DSSTForceModel> forceModels) {
this.forceModels = forceModels;
}
/** {@inheritDoc} */
@SuppressWarnings("unchecked")
@Override
public void init(final FieldODEStateAndDerivative<T> initialState, final T finalTime) {
// Zero
final T zero = field.getZero();
// Build the mean state interpolated at initial point
final FieldSpacecraftState<T> meanStates = mapper.mapArrayToState(zero,
initialState.getPrimaryState(),
initialState.getPrimaryDerivative(),
PropagationType.MEAN);
// Compute short periodic coefficients for this point
for (DSSTForceModel forceModel : forceModels) {
forceModel.updateShortPeriodTerms(forceModel.getParameters(field), meanStates);
}
}
/** {@inheritDoc} */
@SuppressWarnings("unchecked")
@Override
public void handleStep(final FieldODEStateInterpolator<T> interpolator, final boolean isLast) {
// Get the grid points to compute
final T[] interpolationPoints =
interpolationgrid.getGridPoints(interpolator.getPreviousState().getTime(),
interpolator.getCurrentState().getTime());
final FieldSpacecraftState<T>[] meanStates = new FieldSpacecraftState[interpolationPoints.length];
for (int i = 0; i < interpolationPoints.length; ++i) {
// Build the mean state interpolated at grid point
final T time = interpolationPoints[i];
final FieldODEStateAndDerivative<T> sd = interpolator.getInterpolatedState(time);
meanStates[i] = mapper.mapArrayToState(time,
sd.getPrimaryState(),
sd.getPrimaryDerivative(),
PropagationType.MEAN);
}
// Compute short periodic coefficients for this step
for (DSSTForceModel forceModel : forceModels) {
forceModel.updateShortPeriodTerms(forceModel.getParameters(field), meanStates);
}
}
}
}