ModifierGradientConverter.java
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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package org.orekit.estimation.measurements.modifiers;
import org.hipparchus.Field;
import org.hipparchus.analysis.differentiation.Gradient;
import org.hipparchus.analysis.differentiation.GradientField;
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.orbits.FieldCartesianOrbit;
import org.orekit.orbits.FieldOrbit;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.integration.AbstractGradientConverter;
import org.orekit.utils.TimeStampedFieldPVCoordinates;
/**
* Converter for states and parameters arrays.
* @author Bryan Cazabonne
* @since 11.2
*/
public class ModifierGradientConverter extends AbstractGradientConverter {
/** 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
*/
public ModifierGradientConverter(final SpacecraftState state, final int freeStateParameters,
final AttitudeProvider provider) {
super(freeStateParameters);
// Derivative field
final Field<Gradient> field = GradientField.getField(freeStateParameters);
// position always has derivatives
final Vector3D pos = state.getPVCoordinates().getPosition();
final FieldVector3D<Gradient> posG = new FieldVector3D<>(Gradient.variable(freeStateParameters, 0, pos.getX()),
Gradient.variable(freeStateParameters, 1, pos.getY()),
Gradient.variable(freeStateParameters, 2, pos.getZ()));
// velocity may have derivatives or not
final Vector3D vel = state.getPVCoordinates().getVelocity();
final FieldVector3D<Gradient> velG;
if (freeStateParameters > 3) {
velG = new FieldVector3D<>(Gradient.variable(freeStateParameters, 3, vel.getX()),
Gradient.variable(freeStateParameters, 4, vel.getY()),
Gradient.variable(freeStateParameters, 5, vel.getZ()));
} else {
velG = new FieldVector3D<>(Gradient.constant(freeStateParameters, vel.getX()),
Gradient.constant(freeStateParameters, vel.getY()),
Gradient.constant(freeStateParameters, vel.getZ()));
}
// acceleration never has derivatives
final Vector3D acc = state.getPVCoordinates().getAcceleration();
final FieldVector3D<Gradient> accG = new FieldVector3D<>(Gradient.constant(freeStateParameters, acc.getX()),
Gradient.constant(freeStateParameters, acc.getY()),
Gradient.constant(freeStateParameters, acc.getZ()));
// mass never has derivatives
final Gradient dsM = Gradient.constant(freeStateParameters, state.getMass());
final FieldOrbit<Gradient> gOrbit =
new FieldCartesianOrbit<>(new TimeStampedFieldPVCoordinates<>(state.getDate(), posG, velG, accG),
state.getFrame(),
field.getZero().add(state.getMu()));
final FieldAttitude<Gradient> gAttitude;
if (freeStateParameters > 3) {
// compute attitude partial derivatives with respect to position/velocity
gAttitude = provider.getAttitude(gOrbit, gOrbit.getDate(), gOrbit.getFrame());
} else {
// force model does not depend on attitude, don't bother recomputing it
gAttitude = new FieldAttitude<>(field, state.getAttitude());
}
// initialize the list with the state having 0 force model parameters
initStates(new FieldSpacecraftState<>(gOrbit, gAttitude, dsM));
}
}