FieldAbstractAnalyticalPropagator.java

  1. /* Copyright 2002-2020 CS GROUP
  2.  * Licensed to CS GROUP (CS) under one or more
  3.  * contributor license agreements.  See the NOTICE file distributed with
  4.  * this work for additional information regarding copyright ownership.
  5.  * CS licenses this file to You under the Apache License, Version 2.0
  6.  * (the "License"); you may not use this file except in compliance with
  7.  * the License.  You may obtain a copy of the License at
  8.  *
  9.  *   http://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  * Unless required by applicable law or agreed to in writing, software
  12.  * distributed under the License is distributed on an "AS IS" BASIS,
  13.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  * See the License for the specific language governing permissions and
  15.  * limitations under the License.
  16.  */
  17. package org.orekit.propagation.analytical;

  19. import java.util.ArrayList;
  20. import java.util.Collection;
  21. import java.util.Collections;
  22. import java.util.Comparator;
  23. import java.util.List;
  24. import java.util.PriorityQueue;
  25. import java.util.Queue;

  27. import org.hipparchus.Field;
  28. import org.hipparchus.RealFieldElement;
  29. import org.hipparchus.exception.MathRuntimeException;
  30. import org.hipparchus.ode.events.Action;
  31. import org.hipparchus.util.FastMath;
  32. import org.orekit.attitudes.AttitudeProvider;
  33. import org.orekit.attitudes.FieldAttitude;
  34. import org.orekit.errors.OrekitException;
  35. import org.orekit.errors.OrekitInternalError;
  36. import org.orekit.frames.Frame;
  37. import org.orekit.orbits.FieldOrbit;
  38. import org.orekit.propagation.BoundedPropagator;
  39. import org.orekit.propagation.FieldAbstractPropagator;
  40. import org.orekit.propagation.FieldAdditionalStateProvider;
  41. import org.orekit.propagation.FieldBoundedPropagator;
  42. import org.orekit.propagation.FieldSpacecraftState;
  43. import org.orekit.propagation.events.FieldEventDetector;
  44. import org.orekit.propagation.events.FieldEventState;
  45. import org.orekit.propagation.events.FieldEventState.EventOccurrence;
  46. import org.orekit.propagation.sampling.FieldOrekitStepInterpolator;
  47. import org.orekit.time.FieldAbsoluteDate;
  48. import org.orekit.utils.FieldPVCoordinatesProvider;
  49. import org.orekit.utils.TimeStampedFieldPVCoordinates;

  51. /** Common handling of {@link org.orekit.propagation.FieldPropagator} methods for analytical propagators.
  52.  * <p>
  53.  * This abstract class allows to provide easily the full set of {@link
  54.  * org.orekit.propagation.FieldPropagator FieldPropagator} methods, including all propagation
  55.  * modes support and discrete events support for any simple propagation method. Only
  56.  * two methods must be implemented by derived classes: {@link #propagateOrbit(FieldAbsoluteDate)}
  57.  * and {@link #getMass(FieldAbsoluteDate)}. The first method should perform straightforward
  58.  * propagation starting from some internally stored initial state up to the specified target date.
  59.  * </p>
  60.  * @author Luc Maisonobe
  61.  */

  63. public abstract class FieldAbstractAnalyticalPropagator<T extends RealFieldElement<T>> extends FieldAbstractPropagator<T> {

  65.     /** Provider for attitude computation. */
  66.     private FieldPVCoordinatesProvider<T> pvProvider;

  68.     /** Start date of last propagation. */
  69.     private FieldAbsoluteDate<T> lastPropagationStart;

  71.     /** End date of last propagation. */
  72.     private FieldAbsoluteDate<T> lastPropagationEnd;

  74.     /** Initialization indicator of events states. */
  75.     private boolean statesInitialized;

  77.     /** Indicator for last step. */
  78.     private boolean isLastStep;

  80.     /** Event steps. */
  81.     private final Collection<FieldEventState<?, T>> eventsStates;

  83.     /** Build a new instance.
  84.      * @param attitudeProvider provider for attitude computation
  85.      * @param field field used as default
  86.      */
  87.     protected FieldAbstractAnalyticalPropagator(final Field<T> field, final AttitudeProvider attitudeProvider) {
  88.         super(field);
  89.         setAttitudeProvider(attitudeProvider);
  90.         pvProvider           = new FieldLocalPVProvider();
  91.         lastPropagationStart = FieldAbsoluteDate.getPastInfinity(field);
  92.         lastPropagationEnd   = FieldAbsoluteDate.getFutureInfinity(field);
  93.         statesInitialized    = false;
  94.         eventsStates         = new ArrayList<FieldEventState<?, T>>();
  95.     }

  97.     /** {@inheritDoc} */
  98.     public FieldBoundedPropagator<T> getGeneratedEphemeris() {
  99.         return new FieldBoundedPropagatorView(lastPropagationStart, lastPropagationEnd);
  100.     }

  102.     /** {@inheritDoc} */
  103.     public Collection<FieldEventDetector<T>> getEventsDetectors() {
  104.         final List<FieldEventDetector<T>> list = new ArrayList<FieldEventDetector<T>>();
  105.         for (final FieldEventState<?, T> state : eventsStates) {
  106.             list.add(state.getEventDetector());
  107.         }
  108.         return Collections.unmodifiableCollection(list);
  109.     }

  111.     /** {@inheritDoc} */
  112.     public void clearEventsDetectors() {
  113.         eventsStates.clear();
  114.     }
  115.     /** {@inheritDoc} */
  116.     public FieldSpacecraftState<T> propagate(final FieldAbsoluteDate<T> start, final FieldAbsoluteDate<T> target) {
  117.         try {

  119.             initializePropagation();

  121.             lastPropagationStart = start;

  123.             final T dt       = target.durationFrom(start);

  125.             final double epsilon  = FastMath.ulp(dt.getReal());

  127.             FieldSpacecraftState<T> state = updateAdditionalStates(basicPropagate(start));

  129.             // evaluate step size
  130.             final T stepSize;
  131.             if (getMode() == MASTER_MODE) {
  132.                 if (Double.isNaN(getFixedStepSize().getReal())) {
  133.                     stepSize = state.getKeplerianPeriod().divide(100).copySign(dt);
  134.                 } else {
  135.                     stepSize = getFixedStepSize().copySign(dt);
  136.                 }
  137.             } else {
  138.                 stepSize = dt;
  139.             }

  141.             // initialize event detectors
  142.             for (final FieldEventState<?, T> es : eventsStates) {
  143.                 es.init(state, target);
  144.             }

  146.             // initialize step handler
  147.             if (getStepHandler() != null) {
  148.                 getStepHandler().init(state, target);
  149.             }

  151.             // iterate over the propagation range
  152.             statesInitialized = false;
  153.             isLastStep = false;
  154.             do {

  156.                 // go ahead one step size
  157.                 final FieldSpacecraftState<T> previous = state;
  158.                 FieldAbsoluteDate<T> t = previous.getDate().shiftedBy(stepSize);
  159.                 if ((dt.getReal() == 0) || ((dt.getReal() > 0) ^ (t.compareTo(target) <= 0))) {
  160.                     // current step exceeds target
  161.                     t = target;
  162.                 }
  163.                 final FieldSpacecraftState<T> current = updateAdditionalStates(basicPropagate(t));
  164.                 final FieldBasicStepInterpolator interpolator = new FieldBasicStepInterpolator(dt.getReal() >= 0, previous, current);



  168.                 // accept the step, trigger events and step handlers
  169.                 state = acceptStep(interpolator, target, epsilon);
  170.             } while (!isLastStep);
  171.             // return the last computed state
  172.             lastPropagationEnd = state.getDate();
  173.             setStartDate(state.getDate());
  174.             return state;

  176.         } catch (MathRuntimeException mrte) {
  177.             throw OrekitException.unwrap(mrte);
  178.         }
  179.     }

  181.     /** Accept a step, triggering events and step handlers.
  182.      * @param interpolator interpolator for the current step
  183.      * @param target final propagation time
  184.      * @param epsilon threshold for end date detection
  185.      * @return state at the end of the step
  186.           * @exception MathRuntimeException if an event cannot be located
  187.      */
  188.     protected FieldSpacecraftState<T> acceptStep(final FieldBasicStepInterpolator interpolator,
  189.                                          final FieldAbsoluteDate<T> target, final double epsilon)
  190.         throws MathRuntimeException {

  192.         FieldSpacecraftState<T>       previous = interpolator.getPreviousState();
  193.         final FieldSpacecraftState<T> current  = interpolator.getCurrentState();
  194.         FieldBasicStepInterpolator restricted = interpolator;

  196.         // initialize the events states if needed
  197.         if (!statesInitialized) {

  199.             if (!eventsStates.isEmpty()) {
  200.                 // initialize the events states
  201.                 for (final FieldEventState<?, T> state : eventsStates) {
  202.                     state.reinitializeBegin(interpolator);
  203.                 }
  204.             }

  206.             statesInitialized = true;

  208.         }
  209.         // search for next events that may occur during the step
  210.         final int orderingSign = interpolator.isForward() ? +1 : -1;
  211.         final Queue<FieldEventState<?, T>> occurringEvents = new PriorityQueue<>(new Comparator<FieldEventState<?, T>>() {
  212.             /** {@inheritDoc} */
  213.             @Override
  214.             public int compare(final FieldEventState<?, T> es0, final FieldEventState<?, T> es1) {
  215.                 return orderingSign * es0.getEventDate().compareTo(es1.getEventDate());
  216.             }
  217.         });

  219.         boolean doneWithStep = false;
  220.         resetEvents:
  221.         do {

  223.             // Evaluate all event detectors for events
  224.             occurringEvents.clear();
  225.             for (final FieldEventState<?, T> state : eventsStates) {
  226.                 if (state.evaluateStep(interpolator)) {
  227.                     // the event occurs during the current step
  228.                     occurringEvents.add(state);
  229.                 }
  230.             }


  233.             do {
  234.                 eventLoop:
  235.                 while (!occurringEvents.isEmpty()) {
  236.                     // handle the chronologically first event
  237.                     final FieldEventState<?, T> currentEvent = occurringEvents.poll();

  239.                     // get state at event time
  240.                     FieldSpacecraftState<T> eventState = restricted.getInterpolatedState(currentEvent.getEventDate());
  241.                     // try to advance all event states to current time
  242.                     for (final FieldEventState<?, T> state : eventsStates) {
  243.                         if (state != currentEvent && state.tryAdvance(eventState, interpolator)) {
  244.                             // we need to handle another event first
  245.                             // remove event we just updated to prevent heap corruption
  246.                             occurringEvents.remove(state);
  247.                             // add it back to update its position in the heap
  248.                             occurringEvents.add(state);
  249.                             // re-queue the event we were processing
  250.                             occurringEvents.add(currentEvent);
  251.                             continue eventLoop;
  252.                         }
  253.                     }
  254.                     // all event detectors agree we can advance to the current event time
  255.                     final EventOccurrence<T> occurrence = currentEvent.doEvent(eventState);
  256.                     final Action action = occurrence.getAction();
  257.                     isLastStep = action == Action.STOP;
  258.                     if (isLastStep) {
  259.                         // ensure the event is after the root if it is returned STOP
  260.                         // this lets the user integrate to a STOP event and then restart
  261.                         // integration from the same time.
  262.                         eventState = interpolator.getInterpolatedState(occurrence.getStopDate());
  263.                         restricted = new FieldBasicStepInterpolator(restricted.isForward(), previous, eventState);
  264.                     }
  265.                     // handle the first part of the step, up to the event
  266.                     if (getStepHandler() != null) {
  267.                         getStepHandler().handleStep(restricted, isLastStep);
  268.                     }

  270.                     if (isLastStep) {
  271.                         // the event asked to stop integration
  272.                         return eventState;
  273.                     }

  275.                     if (action == Action.RESET_DERIVATIVES || action == Action.RESET_STATE) {
  276.                         // some event handler has triggered changes that
  277.                         // invalidate the derivatives, we need to recompute them
  278.                         final FieldSpacecraftState<T> resetState = occurrence.getNewState();
  279.                         if (resetState != null) {
  280.                             resetIntermediateState(resetState, interpolator.isForward());
  281.                             return resetState;
  282.                         }
  283.                     }
  284.                     // at this point action == Action.CONTINUE or Action.RESET_EVENTS

  286.                     // prepare handling of the remaining part of the step
  287.                     previous = eventState;
  288.                     restricted = new FieldBasicStepInterpolator(restricted.isForward(), eventState, current);

  290.                     if (action == Action.RESET_EVENTS) {
  291.                         continue resetEvents;
  292.                     }

  294.                     // at this pint action == Action.CONTINUE
  295.                     // check if the same event occurs again in the remaining part of the step
  296.                     if (currentEvent.evaluateStep(restricted)) {
  297.                         // the event occurs during the current step
  298.                         occurringEvents.add(currentEvent);
  299.                     }

  301.                 }

  303.                 // last part of the step, after the last event
  304.                 // may be a new event here if the last event modified the g function of
  305.                 // another event detector.
  306.                 for (final FieldEventState<?, T> state : eventsStates) {
  307.                     if (state.tryAdvance(current, interpolator)) {
  308.                         occurringEvents.add(state);
  309.                     }
  310.                 }

  312.             } while (!occurringEvents.isEmpty());

  314.             doneWithStep = true;
  315.         } while (!doneWithStep);

  317.         final T remaining = target.durationFrom(current.getDate());
  318.         if (interpolator.isForward()) {
  319.             isLastStep = remaining.getReal() <  epsilon;
  320.         } else {
  321.             isLastStep = remaining.getReal() > -epsilon;
  322.         }

  324.         // handle the remaining part of the step, after all events if any
  325.         if (getStepHandler() != null) {
  326.             getStepHandler().handleStep(interpolator, isLastStep);
  327.         }
  328.         return current;

  330.     }

  332.     /** Get the mass.
  333.      * @param date target date for the orbit
  334.      * @return mass mass
  335.      */
  336.     protected abstract T getMass(FieldAbsoluteDate<T> date);

  338.     /** Get PV coordinates provider.
  339.      * @return PV coordinates provider
  340.      */
  341.     public FieldPVCoordinatesProvider<T> getPvProvider() {
  342.         return pvProvider;
  343.     }

  345.     /** {@inheritDoc} */
  346.     public <D extends FieldEventDetector<T>> void addEventDetector(final D detector) {
  347.         eventsStates.add(new FieldEventState<D, T>(detector));
  348.     }

  350.     /** Reset an intermediate state.
  351.      * @param state new intermediate state to consider
  352.      * @param forward if true, the intermediate state is valid for
  353.      * propagations after itself
  354.      */
  355.     protected abstract void resetIntermediateState(FieldSpacecraftState<T> state, boolean forward);

  357.     /** Extrapolate an orbit up to a specific target date.
  358.      * @param date target date for the orbit
  359.      * @return extrapolated parameters
  360.      */
  361.     protected abstract FieldOrbit<T> propagateOrbit(FieldAbsoluteDate<T> date);

  363.     /** Propagate an orbit without any fancy features.
  364.      * <p>This method is similar in spirit to the {@link #propagate} method,
  365.      * except that it does <strong>not</strong> call any handler during
  366.      * propagation, nor any discrete events, not additional states. It always
  367.      * stop exactly at the specified date.</p>
  368.      * @param date target date for propagation
  369.      * @return state at specified date
  370.      */
  371.     protected FieldSpacecraftState<T> basicPropagate(final FieldAbsoluteDate<T> date) {
  372.         try {

  374.             // evaluate orbit
  375.             final FieldOrbit<T> orbit = propagateOrbit(date);

  377.             // evaluate attitude
  378.             final FieldAttitude<T> attitude =
  379.                 getAttitudeProvider().getAttitude(pvProvider, date, orbit.getFrame());

  381.             // build raw state
  382.             return new FieldSpacecraftState<>(orbit, attitude, getMass(date));

  384.         } catch (OrekitException oe) {
  385.             throw new OrekitException(oe);
  386.         }
  387.     }

  389.     /** Internal FieldPVCoordinatesProvider<T> for attitude computation. */
  390.     private class FieldLocalPVProvider implements FieldPVCoordinatesProvider<T> {

  392.         /** {@inheritDoc} */
  393.         public TimeStampedFieldPVCoordinates<T> getPVCoordinates(final FieldAbsoluteDate<T> date, final Frame frame) {
  394.             return propagateOrbit(date).getPVCoordinates(frame);
  395.         }

  397.     }

  399.     /** {@link BoundedPropagator} view of the instance. */
  400.     private class FieldBoundedPropagatorView extends FieldAbstractAnalyticalPropagator<T>
  401.         implements FieldBoundedPropagator<T> {

  403.         /** Min date. */
  404.         private final FieldAbsoluteDate<T> minDate;

  406.         /** Max date. */
  407.         private final FieldAbsoluteDate<T> maxDate;

  409.         /** Simple constructor.
  410.          * @param startDate start date of the propagation
  411.          * @param endDate end date of the propagation
  412.          */
  413.         FieldBoundedPropagatorView(final FieldAbsoluteDate<T> startDate, final FieldAbsoluteDate<T> endDate) {
  414.             super(startDate.durationFrom(endDate).getField(), FieldAbstractAnalyticalPropagator.this.getAttitudeProvider());
  415.             if (startDate.compareTo(endDate) <= 0) {
  416.                 minDate = startDate;
  417.                 maxDate = endDate;
  418.             } else {
  419.                 minDate = endDate;
  420.                 maxDate = startDate;
  421.             }

  423.             try {
  424.                 // copy the same additional state providers as the original propagator
  425.                 for (FieldAdditionalStateProvider<T> provider : FieldAbstractAnalyticalPropagator.this.getAdditionalStateProviders()) {
  426.                     addAdditionalStateProvider(provider);
  427.                 }
  428.             } catch (OrekitException oe) {
  429.                 // as the providers are already compatible with each other,
  430.                 // this should never happen
  431.                 throw new OrekitInternalError(null);
  432.             }

  434.         }

  436.         /** {@inheritDoc} */
  437.         public FieldAbsoluteDate<T> getMinDate() {
  438.             return minDate;
  439.         }

  441.         /** {@inheritDoc} */
  442.         public FieldAbsoluteDate<T> getMaxDate() {
  443.             return maxDate;
  444.         }

  446.         /** {@inheritDoc} */
  447.         protected FieldOrbit<T> propagateOrbit(final FieldAbsoluteDate<T> target) {
  448.             return FieldAbstractAnalyticalPropagator.this.propagateOrbit(target);
  449.         }

  451.         /** {@inheritDoc} */
  452.         public T getMass(final FieldAbsoluteDate<T> date) {
  453.             return FieldAbstractAnalyticalPropagator.this.getMass(date);
  454.         }

  456.         /** {@inheritDoc} */
  457.         public TimeStampedFieldPVCoordinates<T> getPVCoordinates(final FieldAbsoluteDate<T> date, final Frame frame) {
  458.             return propagate(date).getPVCoordinates(frame);
  459.         }

  461.         /** {@inheritDoc} */
  462.         public void resetInitialState(final FieldSpacecraftState<T> state) {
  463.             FieldAbstractAnalyticalPropagator.this.resetInitialState(state);
  464.         }

  466.         /** {@inheritDoc} */
  467.         protected void resetIntermediateState(final FieldSpacecraftState<T> state, final boolean forward) {
  468.             FieldAbstractAnalyticalPropagator.this.resetIntermediateState(state, forward);
  469.         }

  471.         /** {@inheritDoc} */
  472.         public FieldSpacecraftState<T> getInitialState() {
  473.             return FieldAbstractAnalyticalPropagator.this.getInitialState();
  474.         }

  476.         /** {@inheritDoc} */
  477.         public Frame getFrame() {
  478.             return FieldAbstractAnalyticalPropagator.this.getFrame();
  479.         }
  480.     }


  483.     /** Internal class for local propagation. */
  484.     private class FieldBasicStepInterpolator implements FieldOrekitStepInterpolator<T> {

  486.         /** Previous state. */
  487.         private final FieldSpacecraftState<T> previousState;

  489.         /** Current state. */
  490.         private final FieldSpacecraftState<T> currentState;

  492.         /** Forward propagation indicator. */
  493.         private final boolean forward;

  495.         /** Simple constructor.
  496.          * @param isForward integration direction indicator
  497.          * @param previousState start of the step
  498.          * @param currentState end of the step
  499.          */
  500.         FieldBasicStepInterpolator(final boolean isForward,
  501.                               final FieldSpacecraftState<T> previousState,
  502.                               final FieldSpacecraftState<T> currentState) {
  503.             this.forward             = isForward;
  504.             this.previousState   = previousState;
  505.             this.currentState    = currentState;
  506.         }

  508.         /** {@inheritDoc} */
  509.         public FieldSpacecraftState<T> getPreviousState() {
  510.             return previousState;
  511.         }

  513.         /** {@inheritDoc} */
  514.         public FieldSpacecraftState<T> getCurrentState() {
  515.             return currentState;
  516.         }

  518.         /** {@inheritDoc} */
  519.         public FieldSpacecraftState<T> getInterpolatedState(final FieldAbsoluteDate<T> date) {

  521.             // compute the basic spacecraft state
  522.             final FieldSpacecraftState<T> basicState = basicPropagate(date);

  524.             // add the additional states
  525.             return updateAdditionalStates(basicState);

  527.         }

  529.         /** {@inheritDoc} */
  530.         public boolean isForward() {
  531.             return forward;
  532.         }

  534.     }

  536. }
Created with JaCoCo 0.8.6.202009150832