DSConverter.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,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.orekit.propagation.numerical;
import java.util.ArrayList;
import java.util.List;
import org.hipparchus.analysis.differentiation.DSFactory;
import org.hipparchus.analysis.differentiation.DerivativeStructure;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.orekit.attitudes.AttitudeProvider;
import org.orekit.attitudes.FieldAttitude;
import org.orekit.forces.ForceModel;
import org.orekit.orbits.FieldCartesianOrbit;
import org.orekit.orbits.FieldOrbit;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.integration.AbstractDSConverter;
import org.orekit.utils.FieldAngularCoordinates;
import org.orekit.utils.FieldPVCoordinates;
import org.orekit.utils.ParameterDriver;
import org.orekit.utils.TimeStampedFieldAngularCoordinates;
import org.orekit.utils.TimeStampedFieldPVCoordinates;
/** Converter for states and parameters arrays.
* @author Luc Maisonobe
* @since 9.0
*/
class DSConverter extends AbstractDSConverter {
/** Dimension of the state. */
private final int freeStateParameters;
/** States with various number of additional parameters for force models. */
private final List<FieldSpacecraftState<DerivativeStructure>> dsStates;
/** Simple constructor.
* @param state regular state
* @param freeStateParameters number of free parameters, either 3 (position) or 6 (position-velocity)
* @param provider provider to use if attitude needs to be recomputed
*/
DSConverter(final SpacecraftState state, final int freeStateParameters, final AttitudeProvider provider) {
super(freeStateParameters);
this.freeStateParameters = freeStateParameters;
// prepare derivation variables, position, optionally velocity
final DSFactory factory = new DSFactory(freeStateParameters, 1);
// position always has derivatives
final Vector3D pos = state.getPVCoordinates().getPosition();
final FieldVector3D<DerivativeStructure> posDS = new FieldVector3D<>(factory.variable(0, pos.getX()),
factory.variable(1, pos.getY()),
factory.variable(2, pos.getZ()));
// velocity may have derivatives or not
final Vector3D vel = state.getPVCoordinates().getVelocity();
final FieldVector3D<DerivativeStructure> velDS;
if (freeStateParameters > 3) {
velDS = new FieldVector3D<>(factory.variable(3, vel.getX()),
factory.variable(4, vel.getY()),
factory.variable(5, vel.getZ()));
} else {
velDS = new FieldVector3D<>(factory.constant(vel.getX()),
factory.constant(vel.getY()),
factory.constant(vel.getZ()));
}
// acceleration never has derivatives
final Vector3D acc = state.getPVCoordinates().getAcceleration();
final FieldVector3D<DerivativeStructure> accDS = new FieldVector3D<>(factory.constant(acc.getX()),
factory.constant(acc.getY()),
factory.constant(acc.getZ()));
// mass never has derivatives
final DerivativeStructure dsM = factory.constant(state.getMass());
final DerivativeStructure dsMu = factory.constant(state.getMu());
final FieldOrbit<DerivativeStructure> dsOrbit =
new FieldCartesianOrbit<>(new TimeStampedFieldPVCoordinates<>(state.getDate(), posDS, velDS, accDS),
state.getFrame(), dsMu);
final FieldAttitude<DerivativeStructure> dsAttitude;
if (freeStateParameters > 3) {
// compute attitude partial derivatives with respect to position/velocity
dsAttitude = provider.getAttitude(dsOrbit, dsOrbit.getDate(), dsOrbit.getFrame());
} else {
// force model does not depend on attitude, don't bother recomputing it
dsAttitude = new FieldAttitude<>(factory.getDerivativeField(), state.getAttitude());
}
// initialize the list with the state having 0 formce model parameters
dsStates = new ArrayList<>();
dsStates.add(new FieldSpacecraftState<>(dsOrbit, dsAttitude, dsM));
}
/** Get the state with the number of parameters consistent with force model.
* @param forceModel force model
* @return state with the number of parameters consistent with force model
*/
public FieldSpacecraftState<DerivativeStructure> getState(final ForceModel forceModel) {
// count the required number of parameters
int nbParams = 0;
for (final ParameterDriver driver : forceModel.getParametersDrivers()) {
if (driver.isSelected()) {
++nbParams;
}
}
// fill in intermediate slots
while (dsStates.size() < nbParams + 1) {
dsStates.add(null);
}
if (dsStates.get(nbParams) == null) {
// it is the first time we need this number of parameters
// we need to create the state
final DSFactory factory = new DSFactory(freeStateParameters + nbParams, 1);
final FieldSpacecraftState<DerivativeStructure> s0 = dsStates.get(0);
// orbit
final FieldPVCoordinates<DerivativeStructure> pv0 = s0.getPVCoordinates();
final FieldOrbit<DerivativeStructure> dsOrbit =
new FieldCartesianOrbit<>(new TimeStampedFieldPVCoordinates<>(s0.getDate().toAbsoluteDate(),
extend(pv0.getPosition(), factory),
extend(pv0.getVelocity(), factory),
extend(pv0.getAcceleration(), factory)),
s0.getFrame(),
extend(s0.getMu(), factory));
// attitude
final FieldAngularCoordinates<DerivativeStructure> ac0 = s0.getAttitude().getOrientation();
final FieldAttitude<DerivativeStructure> dsAttitude =
new FieldAttitude<>(s0.getAttitude().getReferenceFrame(),
new TimeStampedFieldAngularCoordinates<>(dsOrbit.getDate(),
extend(ac0.getRotation(), factory),
extend(ac0.getRotationRate(), factory),
extend(ac0.getRotationAcceleration(), factory)));
// mass
final DerivativeStructure dsM = extend(s0.getMass(), factory);
dsStates.set(nbParams, new FieldSpacecraftState<>(dsOrbit, dsAttitude, dsM));
}
return dsStates.get(nbParams);
}
/** Get the force model parameters.
* @param state state as returned by {@link #getState(ForceModel)}
* @param forceModel force model associated with the parameters
* @return force model parameters
* @since 9.0
*/
public DerivativeStructure[] getParameters(final FieldSpacecraftState<DerivativeStructure> state,
final ForceModel forceModel) {
final DSFactory factory = state.getMass().getFactory();
final ParameterDriver[] drivers = forceModel.getParametersDrivers();
final DerivativeStructure[] parameters = new DerivativeStructure[drivers.length];
int index = freeStateParameters;
for (int i = 0; i < drivers.length; ++i) {
parameters[i] = drivers[i].isSelected() ?
factory.variable(index++, drivers[i].getValue()) :
factory.constant(drivers[i].getValue());
}
return parameters;
}
}