/* Copyright 2002-2017 CS Systèmes d'Information
* Licensed to CS Systèmes d'Information (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.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.PriorityQueue;
import java.util.Queue;
import org.hipparchus.Field;
import org.hipparchus.RealFieldElement;
import org.hipparchus.exception.MathRuntimeException;
import org.hipparchus.util.FastMath;
import org.orekit.attitudes.FieldAttitude;
import org.orekit.attitudes.FieldAttitudeProvider;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitInternalError;
import org.orekit.frames.Frame;
import org.orekit.orbits.FieldOrbit;
import org.orekit.propagation.FieldAbstractPropagator;
import org.orekit.propagation.FieldAdditionalStateProvider;
import org.orekit.propagation.FieldBoundedPropagator;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.propagation.events.FieldEventDetector;
import org.orekit.propagation.events.FieldEventState;
import org.orekit.propagation.events.FieldEventState.EventOccurrence;
import org.orekit.propagation.events.handlers.FieldEventHandler.Action;
import org.orekit.propagation.sampling.FieldOrekitStepInterpolator;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.utils.FieldPVCoordinatesProvider;
import org.orekit.utils.TimeStampedFieldPVCoordinates;
/** Common handling of {@link org.orekit.propagation.FieldPropagator} methods for analytical propagators.
* <p>
* This abstract class allows to provide easily the full set of {@link
* org.orekit.propagation.FieldPropagator FieldPropagator} methods, including all propagation
* modes support and discrete events support for any simple propagation method. Only
* two methods must be implemented by derived classes: {@link #propagateOrbit(FieldAbsoluteDate)}
* and {@link #getMass(FieldAbsoluteDate)}. The first method should perform straightforward
* propagation starting from some internally stored initial state up to the specified target date.
* </p>
* @author Luc Maisonobe
*/
public abstract class FieldAbstractAnalyticalPropagator<T extends RealFieldElement<T>> extends FieldAbstractPropagator<T> {
/** Provider for attitude computation. */
private FieldPVCoordinatesProvider<T> pvProvider;
/** Start date of last propagation. */
private FieldAbsoluteDate<T> lastPropagationStart;
/** End date of last propagation. */
private FieldAbsoluteDate<T> lastPropagationEnd;
/** Initialization indicator of events states. */
private boolean statesInitialized;
/** Indicator for last step. */
private boolean isLastStep;
/** Event steps. */
private final Collection<FieldEventState<?, T>> eventsStates;
/** Build a new instance.
* @param attitudeProvider provider for attitude computation
* @param field field used as default
*/
protected FieldAbstractAnalyticalPropagator(final Field<T> field, final FieldAttitudeProvider<T> attitudeProvider) {
super(field);
setAttitudeProvider(attitudeProvider);
pvProvider = new FieldLocalPVProvider();
lastPropagationStart = FieldAbsoluteDate.getPastInfinity(field);
lastPropagationEnd = FieldAbsoluteDate.getFutureInfinity(field);
statesInitialized = false;
eventsStates = new ArrayList<FieldEventState<?, T>>();
}
/** {@inheritDoc} */
public FieldBoundedPropagator<T> getGeneratedEphemeris() {
return new FieldBoundedPropagatorView(lastPropagationStart, lastPropagationEnd);
}
/** {@inheritDoc} */
public Collection<FieldEventDetector<T>> getEventsDetectors() {
final List<FieldEventDetector<T>> list = new ArrayList<FieldEventDetector<T>>();
for (final FieldEventState<?, T> state : eventsStates) {
list.add(state.getEventDetector());
}
return Collections.unmodifiableCollection(list);
}
/** {@inheritDoc} */
public void clearEventsDetectors() {
eventsStates.clear();
}
/** {@inheritDoc} */
public FieldSpacecraftState<T> propagate(final FieldAbsoluteDate<T> start, final FieldAbsoluteDate<T> target)
throws OrekitException {
try {
lastPropagationStart = start;
final T dt = target.durationFrom(start);
final double epsilon = FastMath.ulp(dt.getReal());
FieldSpacecraftState<T> state = updateAdditionalStates(basicPropagate(start));
// evaluate step size
final T stepSize;
if (getMode() == MASTER_MODE) {
if (Double.isNaN(getFixedStepSize().getReal())) {
stepSize = state.getKeplerianPeriod().divide(100).copySign(dt);
} else {
stepSize = getFixedStepSize().copySign(dt);
}
} else {
stepSize = dt;
}
// initialize event detectors
for (final FieldEventState<?, T> es : eventsStates) {
es.init(state, target);
}
// initialize step handler
if (getStepHandler() != null) {
getStepHandler().init(state, target);
}
// iterate over the propagation range
statesInitialized = false;
isLastStep = false;
do {
// go ahead one step size
final FieldSpacecraftState<T> previous = state;
FieldAbsoluteDate<T> t = previous.getDate().shiftedBy(stepSize);
if ((dt.getReal() == 0) || ((dt.getReal() > 0) ^ (t.compareTo(target) <= 0))) {
// current step exceeds target
t = target;
}
final FieldSpacecraftState<T> current = updateAdditionalStates(basicPropagate(t));
final FieldBasicStepInterpolator interpolator = new FieldBasicStepInterpolator(dt.getReal() >= 0, previous, current);
// accept the step, trigger events and step handlers
state = acceptStep(interpolator, target, epsilon);
} while (!isLastStep);
// return the last computed state
lastPropagationEnd = state.getDate();
setStartDate(state.getDate());
return state;
} catch (OrekitException pe) {
throw pe;
} catch (MathRuntimeException mrte) {
throw OrekitException.unwrap(mrte);
}
}
/** Accept a step, triggering events and step handlers.
* @param interpolator interpolator for the current step
* @param target final propagation time
* @param epsilon threshold for end date detection
* @return state at the end of the step
* @exception OrekitException if the switching function cannot be evaluated
* @exception MathRuntimeException if an event cannot be located
*/
protected FieldSpacecraftState<T> acceptStep(final FieldBasicStepInterpolator interpolator,
final FieldAbsoluteDate<T> target, final double epsilon)
throws OrekitException, MathRuntimeException {
FieldSpacecraftState<T> previous = interpolator.getPreviousState();
final FieldSpacecraftState<T> current = interpolator.getCurrentState();
// initialize the events states if needed
if (!statesInitialized) {
if (!eventsStates.isEmpty()) {
// initialize the events states
for (final FieldEventState<?, T> state : eventsStates) {
state.reinitializeBegin(interpolator);
}
}
statesInitialized = true;
}
// search for next events that may occur during the step
final int orderingSign = interpolator.isForward() ? +1 : -1;
final Queue<FieldEventState<?, T>> occurringEvents = new PriorityQueue<>(new Comparator<FieldEventState<?, T>>() {
/** {@inheritDoc} */
@Override
public int compare(final FieldEventState<?, T> es0, final FieldEventState<?, T> es1) {
return orderingSign * es0.getEventDate().compareTo(es1.getEventDate());
}
});
for (final FieldEventState<?, T> state : eventsStates) {
if (state.evaluateStep(interpolator)) {
// the event occurs during the current step
occurringEvents.add(state);
}
}
FieldBasicStepInterpolator restricted = interpolator;
do {
eventLoop:
while (!occurringEvents.isEmpty()) {
// handle the chronologically first event
final FieldEventState<?, T> currentEvent = occurringEvents.poll();
// get state at event time
FieldSpacecraftState<T> eventState = restricted.getInterpolatedState(currentEvent.getEventDate());
// try to advance all event states to current time
for (final FieldEventState<?, T> state : eventsStates) {
if (state != currentEvent && state.tryAdvance(eventState, interpolator)) {
// we need to handle another event first
occurringEvents.add(currentEvent);
occurringEvents.remove(state); // remove if already has pending event
occurringEvents.add(state);
continue eventLoop;
}
}
// all event detectors agree we can advance to the current event time
final EventOccurrence<T> occurrence = currentEvent.doEvent(eventState);
final Action action = occurrence.getAction();
isLastStep = action == Action.STOP;
if (isLastStep) {
// ensure the event is after the root if it is returned STOP
// this lets the user integrate to a STOP event and then restart
// integration from the same time.
eventState = interpolator.getInterpolatedState(occurrence.getStopDate());
restricted = new FieldBasicStepInterpolator(restricted.isForward(), previous, eventState);
}
// handle the first part of the step, up to the event
if (getStepHandler() != null) {
getStepHandler().handleStep(restricted, isLastStep);
}
if (isLastStep) {
// the event asked to stop integration
return eventState;
}
if (action == Action.RESET_DERIVATIVES || action == Action.RESET_STATE) {
// some event handler has triggered changes that
// invalidate the derivatives, we need to recompute them
final FieldSpacecraftState<T> resetState = occurrence.getNewState();
if (resetState != null) {
resetIntermediateState( resetState, interpolator.isForward());
return resetState;
}
}
// at this point we know action == Action.CONTINUE
// prepare handling of the remaining part of the step
previous = eventState;
restricted = new FieldBasicStepInterpolator(restricted.isForward(), eventState, current);
// check if the same event occurs again in the remaining part of the step
if (currentEvent.evaluateStep(restricted)) {
// the event occurs during the current step
occurringEvents.add(currentEvent);
}
}
// last part of the step, after the last event
// may be a new event here if the last event modified the g function of
// another event detector.
for (final FieldEventState<?, T> state : eventsStates) {
if (state.tryAdvance(current, interpolator)) {
occurringEvents.add(state);
}
}
} while (!occurringEvents.isEmpty());
final T remaining = target.durationFrom(current.getDate());
if (interpolator.isForward()) {
isLastStep = remaining.getReal() < epsilon;
} else {
isLastStep = remaining.getReal() > -epsilon;
}
// handle the remaining part of the step, after all events if any
if (getStepHandler() != null) {
getStepHandler().handleStep(interpolator, isLastStep);
}
return current;
}
/** Get the mass.
* @param date target date for the orbit
* @return mass mass
* @exception OrekitException if some parameters are out of bounds
*/
protected abstract T getMass(FieldAbsoluteDate<T> date)
throws OrekitException;
/** Get PV coordinates provider.
* @return PV coordinates provider
*/
public FieldPVCoordinatesProvider<T> getPvProvider() {
return pvProvider;
}
/** {@inheritDoc} */
public <D extends FieldEventDetector<T>> void addEventDetector(final D detector) {
eventsStates.add(new FieldEventState<D, T>(detector));
}
/** Reset an intermediate state.
* @param state new intermediate state to consider
* @param forward if true, the intermediate state is valid for
* propagations after itself
* @exception OrekitException if initial state cannot be reset
*/
protected abstract void resetIntermediateState(FieldSpacecraftState<T> state, boolean forward)
throws OrekitException;
/** Extrapolate an orbit up to a specific target date.
* @param date target date for the orbit
* @return extrapolated parameters
* @exception OrekitException if some parameters are out of bounds
*/
protected abstract FieldOrbit<T> propagateOrbit(FieldAbsoluteDate<T> date)
throws OrekitException;
/** Propagate an orbit without any fancy features.
* <p>This method is similar in spirit to the {@link #propagate} method,
* except that it does <strong>not</strong> call any handler during
* propagation, nor any discrete events, not additional states. It always
* stop exactly at the specified date.</p>
* @param date target date for propagation
* @return state at specified date
* @exception OrekitException if propagation cannot reach specified date
*/
protected FieldSpacecraftState<T> basicPropagate(final FieldAbsoluteDate<T> date) throws OrekitException {
try {
// evaluate orbit
final FieldOrbit<T> orbit = propagateOrbit(date);
// evaluate attitude
final FieldAttitude<T> attitude =
getAttitudeProvider().getAttitude(pvProvider, date, orbit.getFrame());
// build raw state
return new FieldSpacecraftState<T>(orbit, attitude, getMass(date));
} catch (OrekitException oe) {
throw new OrekitException(oe);
}
}
/** Internal FieldPVCoordinatesProvider<T> for attitude computation. */
private class FieldLocalPVProvider implements FieldPVCoordinatesProvider<T> {
/** {@inheritDoc} */
public TimeStampedFieldPVCoordinates<T> getPVCoordinates(final FieldAbsoluteDate<T> date, final Frame frame)
throws OrekitException {
return propagateOrbit(date).getPVCoordinates(frame);
}
}
/** {@link BoundedPropagator} view of the instance. */
private class FieldBoundedPropagatorView extends FieldAbstractAnalyticalPropagator<T>
implements FieldBoundedPropagator<T> {
/** Min date. */
private final FieldAbsoluteDate<T> minDate;
/** Max date. */
private final FieldAbsoluteDate<T> maxDate;
/** Simple constructor.
* @param startDate start date of the propagation
* @param endDate end date of the propagation
*/
FieldBoundedPropagatorView(final FieldAbsoluteDate<T> startDate, final FieldAbsoluteDate<T> endDate) {
super(startDate.durationFrom(endDate).getField(), FieldAbstractAnalyticalPropagator.this.getAttitudeProvider());
if (startDate.compareTo(endDate) <= 0) {
minDate = startDate;
maxDate = endDate;
} else {
minDate = endDate;
maxDate = startDate;
}
try {
// copy the same additional state providers as the original propagator
for (FieldAdditionalStateProvider<T> provider : FieldAbstractAnalyticalPropagator.this.getAdditionalStateProviders()) {
addAdditionalStateProvider(provider);
}
} catch (OrekitException oe) {
// as the providers are already compatible with each other,
// this should never happen
throw new OrekitInternalError(null);
}
}
/** {@inheritDoc} */
public FieldAbsoluteDate<T> getMinDate() {
return minDate;
}
/** {@inheritDoc} */
public FieldAbsoluteDate<T> getMaxDate() {
return maxDate;
}
/** {@inheritDoc} */
protected FieldOrbit<T> propagateOrbit(final FieldAbsoluteDate<T> target)
throws OrekitException {
return FieldAbstractAnalyticalPropagator.this.propagateOrbit(target);
}
/** {@inheritDoc} */
public T getMass(final FieldAbsoluteDate<T> date) throws OrekitException {
return FieldAbstractAnalyticalPropagator.this.getMass(date);
}
/** {@inheritDoc} */
public TimeStampedFieldPVCoordinates<T> getPVCoordinates(final FieldAbsoluteDate<T> date, final Frame frame)
throws OrekitException {
return propagate(date).getPVCoordinates(frame);
}
/** {@inheritDoc} */
public void resetInitialState(final FieldSpacecraftState<T> state) throws OrekitException {
FieldAbstractAnalyticalPropagator.this.resetInitialState(state);
}
/** {@inheritDoc} */
protected void resetIntermediateState(final FieldSpacecraftState<T> state, final boolean forward)
throws OrekitException {
FieldAbstractAnalyticalPropagator.this.resetIntermediateState(state, forward);
}
/** {@inheritDoc} */
public FieldSpacecraftState<T> getInitialState() throws OrekitException {
return FieldAbstractAnalyticalPropagator.this.getInitialState();
}
/** {@inheritDoc} */
public Frame getFrame() {
return FieldAbstractAnalyticalPropagator.this.getFrame();
}
}
/** Internal class for local propagation. */
private class FieldBasicStepInterpolator implements FieldOrekitStepInterpolator<T> {
/** Previous state. */
private final FieldSpacecraftState<T> previousState;
/** Current state. */
private final FieldSpacecraftState<T> currentState;
/** Forward propagation indicator. */
private final boolean forward;
/** Simple constructor.
* @param isForward integration direction indicator
* @param previousState start of the step
* @param currentState end of the step
*/
FieldBasicStepInterpolator(final boolean isForward,
final FieldSpacecraftState<T> previousState,
final FieldSpacecraftState<T> currentState) {
this.forward = isForward;
this.previousState = previousState;
this.currentState = currentState;
}
/** {@inheritDoc} */
public FieldSpacecraftState<T> getPreviousState() {
return previousState;
}
/** {@inheritDoc} */
public FieldSpacecraftState<T> getCurrentState() {
return currentState;
}
/** {@inheritDoc} */
public FieldSpacecraftState<T> getInterpolatedState(final FieldAbsoluteDate<T> date)
throws OrekitException {
// compute the basic spacecraft state
final FieldSpacecraftState<T> basicState = basicPropagate(date);
// add the additional states
return updateAdditionalStates(basicState);
}
/** {@inheritDoc} */
public boolean isForward() {
return forward;
}
}
}