AbstractGradientConverter.java
/* Copyright 2002-2026 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;
import java.util.ArrayList;
import java.util.List;
import org.hipparchus.analysis.differentiation.Gradient;
import org.hipparchus.analysis.differentiation.GradientField;
import org.hipparchus.geometry.euclidean.threed.FieldRotation;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.orekit.attitudes.AttitudeProvider;
import org.orekit.attitudes.FieldAttitude;
import org.orekit.orbits.CartesianOrbit;
import org.orekit.orbits.OrbitType;
import org.orekit.orbits.FieldOrbit;
import org.orekit.orbits.PositionAngleBased;
import org.orekit.orbits.PositionAngleType;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.utils.DerivativeStateUtils;
import org.orekit.utils.FieldPVCoordinates;
import org.orekit.utils.FieldAbsolutePVCoordinates;
import org.orekit.utils.ParameterDriver;
import org.orekit.utils.ParameterDriversProvider;
import org.orekit.utils.TimeStampedFieldAngularCoordinates;
import org.orekit.utils.TimeSpanMap.Span;
/** Converter for states and parameters arrays.
* @author Luc Maisonobe
* @author Bryan Cazabonne
* @since 10.2
*/
public abstract class AbstractGradientConverter {
/** Dimension of the state. */
private final int freeStateParameters;
/** States with various number of additional parameters. */
private final List<FieldSpacecraftState<Gradient>> gStates;
/** Simple constructor.
* @param freeStateParameters number of free parameters
*/
protected AbstractGradientConverter(final int freeStateParameters) {
this.freeStateParameters = freeStateParameters;
this.gStates = new ArrayList<>();
}
/** Get the number of free state parameters.
* @return number of free state parameters
*/
public int getFreeStateParameters() {
return freeStateParameters;
}
/** Initialize first state with 0 parameters.
* @param zeroParametersState state with zero parameters
* @since 11.2
*/
public void initStates(final FieldSpacecraftState<Gradient> zeroParametersState) {
gStates.clear();
gStates.add(zeroParametersState);
}
/** Add zero derivatives.
* @param original original scalar
* @param freeParameters total number of free parameters in the gradient
* @return extended scalar
*/
private Gradient extend(final Gradient original, final int freeParameters) {
final double[] originalDerivatives = original.getGradient();
final double[] extendedDerivatives = new double[freeParameters];
System.arraycopy(originalDerivatives, 0, extendedDerivatives, 0, originalDerivatives.length);
return new Gradient(original.getValue(), extendedDerivatives);
}
/** Add zero derivatives.
* @param original original date
* @param freeParameters total number of free parameters in the gradient
* @return extended date
*/
private FieldAbsoluteDate<Gradient> extend(final FieldAbsoluteDate<Gradient> original, final int freeParameters) {
final AbsoluteDate date = original.toAbsoluteDate();
return new FieldAbsoluteDate<>(date, extend(original.durationFrom(date), freeParameters));
}
/** Add zero derivatives.
* @param original original vector
* @param freeParameters total number of free parameters in the gradient
* @return extended vector
*/
private FieldVector3D<Gradient> extend(final FieldVector3D<Gradient> original, final int freeParameters) {
return new FieldVector3D<>(extend(original.getX(), freeParameters),
extend(original.getY(), freeParameters),
extend(original.getZ(), freeParameters));
}
/** Add zero derivatives.
* @param original original rotation
* @param freeParameters total number of free parameters in the gradient
* @return extended rotation
*/
private FieldRotation<Gradient> extend(final FieldRotation<Gradient> original, final int freeParameters) {
return new FieldRotation<>(extend(original.getQ0(), freeParameters),
extend(original.getQ1(), freeParameters),
extend(original.getQ2(), freeParameters),
extend(original.getQ3(), freeParameters),
false);
}
/** Add zero derivatives.
* @param original original angular coordinates
* @param freeParameters total number of free parameters in the gradient
* @return extended angular coordinates
*/
private TimeStampedFieldAngularCoordinates<Gradient> extend(final TimeStampedFieldAngularCoordinates<Gradient> original,
final int freeParameters) {
return new TimeStampedFieldAngularCoordinates<>(extend(original.getDate(), freeParameters),
extend(original.getRotation(), freeParameters),
extend(original.getRotationRate(), freeParameters),
extend(original.getRotationAcceleration(), freeParameters));
}
/** Add zero derivatives.
* @param original original attitude
* @param freeParameters total number of free parameters in the gradient
* @return extended rotation
*/
private FieldAttitude<Gradient> extend(final FieldAttitude<Gradient> original, final int freeParameters) {
return new FieldAttitude<>(original.getReferenceFrame(),
extend(original.getOrientation(), freeParameters));
}
/** Add zero derivatives.
* @param orbit original orbit
* @param freeParameters number of free parameters
* @return gradient orbit
* @since 14.0
*/
private FieldOrbit<Gradient> extend(final FieldOrbit<Gradient> orbit, final int freeParameters) {
final PositionAngleType positionAngleType = orbit instanceof PositionAngleBased<?> pab ?
pab.getCachedPositionAngleType() :
PositionAngleType.MEAN;
// original state
final Gradient[] originalState = new Gradient[6];
orbit.getType().mapOrbitToArray(orbit, positionAngleType, originalState, null);
// extended state
final Gradient[] extendedState = new Gradient[originalState.length];
for (int i = 0; i < originalState.length; i++) {
extendedState[i] = extend(originalState[i], freeParameters);
}
return orbit.getType().mapArrayToOrbit(extendedState, null, positionAngleType,
extend(orbit.getDate(), freeParameters),
extend(orbit.getMu(), freeParameters),
orbit.getFrame());
}
/** Add zero derivatives.
* @param pv original Cartesian coordinates
* @param freeParameters number of free parameters
* @return gradient Cartesian coordinates
* @since 14.0
*/
private FieldPVCoordinates<Gradient> extend(final FieldPVCoordinates<Gradient> pv, final int freeParameters) {
return new FieldPVCoordinates<>(extend(pv.getPosition(), freeParameters),
extend(pv.getVelocity(), freeParameters),
extend(pv.getAcceleration(), freeParameters));
}
/** Add zero derivatives.
* @param apv original Cartesian coordinates
* @param freeParameters number of free parameters
* @return gradient Cartesian coordinates
* @since 14.0
*/
private FieldAbsolutePVCoordinates<Gradient> extend(final FieldAbsolutePVCoordinates<Gradient> apv,
final int freeParameters) {
return new FieldAbsolutePVCoordinates<>(apv.getFrame(),
extend(apv.getDate(), freeParameters),
extend(apv.getPVCoordinates(), freeParameters));
}
/** Process a state into a Gradient version without force model parameter.
* @param state state
* @param freeStateParameters number of free parameters
* @param provider attitude provider
* @return Gradient version of the state
* @since 12.0
*/
public static FieldSpacecraftState<Gradient> buildBasicGradientSpacecraftState(final SpacecraftState state,
final int freeStateParameters,
final AttitudeProvider provider) {
// Derivative field
final GradientField field = GradientField.getField(freeStateParameters);
if (state.isOrbitDefined()) {
final CartesianOrbit cartesianOrbit = (CartesianOrbit) OrbitType.CARTESIAN.convertType(state.getOrbit());
final SpacecraftState cartesianState = new SpacecraftState(cartesianOrbit, state.getAttitude()).withMass(state.getMass());
return DerivativeStateUtils.buildSpacecraftStateGradient(field, cartesianState, provider);
} else {
return DerivativeStateUtils.buildSpacecraftStateGradient(field, state, provider);
}
}
/**
* Get the state with the number of parameters consistent with parametric model.
* @param parametricModel parametric model
* @return state with the number of parameters consistent with parametric model
*/
public FieldSpacecraftState<Gradient> getState(final ParameterDriversProvider parametricModel) {
// count the required number of parameters
int nbParams = 0;
for (final ParameterDriver driver : parametricModel.getParametersDrivers()) {
if (driver.isSelected()) {
nbParams += driver.getNbOfValues();
}
}
// fill in intermediate slots
while (gStates.size() < nbParams + 1) {
gStates.add(null);
}
if (gStates.get(nbParams) == null) {
// it is the first time we need this number of parameters
// we need to create the state
final int freeParameters = freeStateParameters + nbParams;
final FieldSpacecraftState<Gradient> s0 = gStates.getFirst();
// attitude
final FieldAttitude<Gradient> gAttitude = extend(s0.getAttitude(), freeParameters);
// orbit or absolute position-velocity coordinates
final FieldSpacecraftState<Gradient> spacecraftState =
s0.isOrbitDefined() ?
new FieldSpacecraftState<>(extend(s0.getOrbit(), freeParameters), gAttitude) :
new FieldSpacecraftState<>(extend(s0.getAbsPVA(), freeParameters), gAttitude);
// mass
final Gradient gMass = extend(s0.getMass(), freeParameters);
gStates.set(nbParams, spacecraftState.withMass(gMass));
}
return gStates.get(nbParams);
}
/** Get the parametric model parameters, return gradient values for each span of each driver (several gradient
* values for each parameter).
* Different from {@link #getParametersAtStateDate(FieldSpacecraftState, ParameterDriversProvider)}
* which return a Gradient list containing for each driver the gradient value at state date (only 1 gradient
* value for each parameter).
* @param state state as returned by {@link #getState(ParameterDriversProvider) getState(parametricModel)}
* @param parametricModel parametric model associated with the parameters
* @return parametric model parameters (for all span of each driver)
*/
public Gradient[] getParameters(final FieldSpacecraftState<Gradient> state,
final ParameterDriversProvider parametricModel) {
final int freeParameters = state.getMass().getFreeParameters();
final List<ParameterDriver> drivers = parametricModel.getParametersDrivers();
int sizeDrivers = 0;
for ( ParameterDriver driver : drivers) {
sizeDrivers += driver.getNbOfValues();
}
final Gradient[] parameters = new Gradient[sizeDrivers];
int index = freeStateParameters;
int i = 0;
for (ParameterDriver driver : drivers) {
// Loop on the spans
for (Span<Double> span = driver.getValueSpanMap().getFirstSpan(); span != null; span = span.next()) {
parameters[i++] = driver.isSelected() ?
Gradient.variable(freeParameters, index++, span.getData()) :
Gradient.constant(freeParameters, span.getData());
}
}
return parameters;
}
/** Get the parametric model parameters, return gradient values at state date for each driver (only 1 gradient
* value for each parameter).
* Different from {@link #getParameters(FieldSpacecraftState, ParameterDriversProvider)}
* which return a Gradient list containing for each driver the gradient values for each span value (several gradient
* values for each parameter).
* @param state state as returned by {@link #getState(ParameterDriversProvider) getState(parametricModel)}
* @param parametricModel parametric model associated with the parameters
* @return parametric model parameters (for all span of each driver)
*/
public Gradient[] getParametersAtStateDate(final FieldSpacecraftState<Gradient> state,
final ParameterDriversProvider parametricModel) {
final int freeParameters = state.getMass().getFreeParameters();
final List<ParameterDriver> drivers = parametricModel.getParametersDrivers();
final AbsoluteDate date = state.getDate().toAbsoluteDate();
final Gradient[] parameters = new Gradient[drivers.size()];
int index = freeStateParameters;
int i = 0;
for (ParameterDriver driver : drivers) {
for (Span<String> span = driver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {
if (span.getData().equals(driver.getNameSpan(date))) {
parameters[i++] = driver.isSelected() ?
Gradient.variable(freeParameters, index, driver.getValue(date)) :
Gradient.constant(freeParameters, driver.getValue(date));
}
index = driver.isSelected() ? index + 1 : index;
}
}
return parameters;
}
}