AdapterPropagator.java
- /* Copyright 2002-2021 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.analytical;
- import java.util.ArrayList;
- import java.util.Collections;
- import java.util.List;
- import java.util.Map;
- import org.orekit.errors.OrekitException;
- import org.orekit.errors.OrekitMessages;
- import org.orekit.orbits.Orbit;
- import org.orekit.propagation.Propagator;
- import org.orekit.propagation.SpacecraftState;
- import org.orekit.time.AbsoluteDate;
- /** Orbit propagator that adapts an underlying propagator, adding {@link
- * DifferentialEffect differential effects}.
- * <p>
- * This propagator is used when a reference propagator does not handle
- * some effects that we need. A typical example would be an ephemeris
- * that was computed for a reference orbit, and we want to compute a
- * station-keeping maneuver on top of this ephemeris, changing its
- * final state. The principal is to add one or more {@link
- * org.orekit.forces.maneuvers.SmallManeuverAnalyticalModel small maneuvers
- * analytical models} to it and use it as a new propagator, which takes the
- * maneuvers into account.
- * </p>
- * <p>
- * From a space flight dynamics point of view, this is a differential
- * correction approach. From a computer science point of view, this is
- * a use of the decorator design pattern.
- * </p>
- * @see Propagator
- * @see org.orekit.forces.maneuvers.SmallManeuverAnalyticalModel
- * @author Luc Maisonobe
- */
- public class AdapterPropagator extends AbstractAnalyticalPropagator {
- /** Interface for orbit differential effects. */
- public interface DifferentialEffect {
- /** Apply the effect to a {@link SpacecraftState spacecraft state}.
- * <p>
- * Applying the effect may be a no-op in some cases. A typical example
- * is maneuvers, for which the state is changed only for time <em>after</em>
- * the maneuver occurrence.
- * </p>
- * @param original original state <em>without</em> the effect
- * @return updated state at the same date, taking the effect
- * into account if meaningful
- */
- SpacecraftState apply(SpacecraftState original);
- }
- /** Underlying reference propagator. */
- private Propagator reference;
- /** Effects to add. */
- private List<DifferentialEffect> effects;
- /** Build a propagator from an underlying reference propagator.
- * <p>The reference propagator can be almost anything, numerical,
- * analytical, and even an ephemeris. It may already take some maneuvers
- * into account.</p>
- * @param reference reference propagator
- */
- public AdapterPropagator(final Propagator reference) {
- super(reference.getAttitudeProvider());
- this.reference = reference;
- this.effects = new ArrayList<DifferentialEffect>();
- }
- /** Add a differential effect.
- * @param effect differential effect
- */
- public void addEffect(final DifferentialEffect effect) {
- effects.add(effect);
- }
- /** Get the reference propagator.
- * @return reference propagator
- */
- public Propagator getPropagator() {
- return reference;
- }
- /** Get the differential effects.
- * @return differential effects models, as an unmodifiable list
- */
- public List<DifferentialEffect> getEffects() {
- return Collections.unmodifiableList(effects);
- }
- /** {@inheritDoc} */
- public SpacecraftState getInitialState() {
- return reference.getInitialState();
- }
- /** {@inheritDoc} */
- @Override
- public void resetInitialState(final SpacecraftState state) {
- reference.resetInitialState(state);
- }
- /** {@inheritDoc} */
- protected void resetIntermediateState(final SpacecraftState state, final boolean forward) {
- if (reference instanceof AbstractAnalyticalPropagator) {
- ((AbstractAnalyticalPropagator) reference).resetIntermediateState(state, forward);
- } else {
- throw new OrekitException(OrekitMessages.NON_RESETABLE_STATE);
- }
- }
- /** {@inheritDoc} */
- @Override
- protected SpacecraftState basicPropagate(final AbsoluteDate date) {
- // compute reference state
- SpacecraftState state = reference.propagate(date);
- final Map<String, double[]> before = state.getAdditionalStates();
- // add all the effects
- for (final DifferentialEffect effect : effects) {
- state = effect.apply(state);
- }
- // forward additional states from the reference propagator
- for (final Map.Entry<String, double[]> entry : before.entrySet()) {
- if (!state.hasAdditionalState(entry.getKey())) {
- state = state.addAdditionalState(entry.getKey(), entry.getValue());
- }
- }
- return state;
- }
- /** {@inheritDoc} */
- protected Orbit propagateOrbit(final AbsoluteDate date) {
- return basicPropagate(date).getOrbit();
- }
- /** {@inheritDoc}*/
- protected double getMass(final AbsoluteDate date) {
- return basicPropagate(date).getMass();
- }
- }