DateDetector.java

  1. /* Copyright 2002-2025 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.events;

  19. import java.util.ArrayList;
  20. import java.util.Collections;
  21. import java.util.List;

  23. import org.hipparchus.ode.events.Action;
  24. import org.orekit.errors.OrekitIllegalArgumentException;
  25. import org.orekit.errors.OrekitMessages;
  26. import org.orekit.propagation.SpacecraftState;
  27. import org.orekit.propagation.events.handlers.EventHandler;
  28. import org.orekit.propagation.events.handlers.StopOnEvent;
  29. import org.orekit.propagation.events.intervals.DateDetectionAdaptableIntervalFactory;
  30. import org.orekit.time.AbsoluteDate;
  31. import org.orekit.time.TimeStamped;

  33. /** Finder for date events.
  34.  * <p>This class finds date events (i.e. occurrence of some predefined dates).</p>
  35.  * <p>As of version 5.1, it is an enhanced date detector:</p>
  36.  * <ul>
  37.  *   <li>it can be defined without prior date ({@link #DateDetector(TimeStamped...)})</li>
  38.  *   <li>several dates can be added ({@link #addEventDate(AbsoluteDate)})</li>
  39.  * </ul>
  40.  * <p>The gap between the added dates must be more than the minGap.</p>
  41.  * <p>The default implementation behavior is to {@link Action#STOP stop}
  42.  * propagation at the first event date occurrence. This can be changed by calling
  43.  * {@link #withHandler(EventHandler)} after construction.</p>
  44.  * @see org.orekit.propagation.Propagator#addEventDetector(EventDetector)
  45.  * @author Luc Maisonobe
  46.  * @author Pascal Parraud
  47.  */
  48. public class DateDetector extends AbstractDetector<DateDetector> implements TimeStamped {

  50.     /** Default value for max check.
  51.      * @since 12.0
  52.      */
  53.     public static final double DEFAULT_MAX_CHECK = DateDetectionAdaptableIntervalFactory.DEFAULT_MAX_CHECK;

  55.     /** Default value for minimum gap between added dates.
  56.      * @since 12.0
  57.      */
  58.     public static final double DEFAULT_MIN_GAP = 1.0;

  60.     /** Default value for convergence threshold.
  61.      * @since 12.0
  62.      */
  63.     public static final double DEFAULT_THRESHOLD = 1.0e-10;

  65.     /** Minimum gap between added dates.
  66.      * @since 12.0
  67.      */
  68.     private final double minGap;

  70.     /** Last date for g computation. */
  71.     private AbsoluteDate gDate;

  73.     /** List of event dates. */
  74.     private final ArrayList<EventDate> eventDateList;

  76.     /** Current event date. */
  77.     private int currentIndex;

  79.     /** Build a new instance.
  80.      * <p>First event dates are set here, but others can be
  81.      * added later with {@link #addEventDate(AbsoluteDate)}, although the max. check should probably be changed then.</p>
  82.      * @param dates list of event dates
  83.      * @see #addEventDate(AbsoluteDate)
  84.      * @since 12.0
  85.      */
  86.     public DateDetector(final TimeStamped... dates) {
  87.         this(new EventDetectionSettings(DateDetectionAdaptableIntervalFactory.getDatesDetectionConstantInterval(dates),
  88.                         DEFAULT_THRESHOLD, EventDetectionSettings.DEFAULT_MAX_ITER),
  89.                 new StopOnEvent(), DEFAULT_MIN_GAP, dates);
  90.     }

  92.     /** Build a new instance from a single time.
  93.      * <p>First event dates are set here, but others can be
  94.      * added later with {@link #addEventDate(AbsoluteDate)}, although the max. check should probably be changed then.</p>
  95.      * @param date event date
  96.      * @see #addEventDate(AbsoluteDate)
  97.      * @since 13.0
  98.      */
  99.     public DateDetector(final AbsoluteDate date) {
  100.         this((TimeStamped) date);
  101.     }

  103.     /** Build a new instance.
  104.      * <p>First event dates are set here, but others can be
  105.      * added later with {@link #addEventDate(AbsoluteDate)}, although the max. check should probably be changed then.</p>
  106.      * @param minGap minimum gap between added dates (s)
  107.      * @param dates list of event dates
  108.      * @see #addEventDate(AbsoluteDate)
  109.      * @since 13.0
  110.      */
  111.     public DateDetector(final double minGap, final TimeStamped... dates) {
  112.         this(new EventDetectionSettings(DateDetectionAdaptableIntervalFactory.getDatesDetectionConstantInterval(dates),
  113.                                         DEFAULT_THRESHOLD, EventDetectionSettings.DEFAULT_MAX_ITER),
  114.              new StopOnEvent(), minGap, dates);
  115.     }

  117.     /** Build a new instance from a single time.
  118.      * <p>First event dates are set here, but others can be
  119.      * added later with {@link #addEventDate(AbsoluteDate)}, although the max. check should probably be changed then.</p>
  120.      * @param minGap minimum gap between added dates (s)
  121.      * @param date event date
  122.      * @see #addEventDate(AbsoluteDate)
  123.      * @since 13.0
  124.      */
  125.     public DateDetector(final double minGap, final AbsoluteDate date) {
  126.         this(minGap, (TimeStamped) date);
  127.     }

  129.     /** Protected constructor with full parameters.
  130.      * <p>
  131.      * This constructor is not public as users are expected to use the builder
  132.      * API with the various {@code withXxx()} methods to set up the instance
  133.      * in a readable manner without using a huge amount of parameters.
  134.      * </p>
  135.      * @param detectionSettings detection settings
  136.      * @param handler event handler to call at event occurrences
  137.      * @param minGap minimum gap between added dates (s)
  138.      * @param dates list of event dates
  139.      * @since 12.2
  140.      */
  141.     protected DateDetector(final EventDetectionSettings detectionSettings,
  142.                            final EventHandler handler, final double minGap, final TimeStamped... dates) {
  143.         super(detectionSettings, handler);
  144.         this.currentIndex  = -1;
  145.         this.gDate         = null;
  146.         this.eventDateList = new ArrayList<>();
  147.         this.minGap        = minGap;
  148.         for (final TimeStamped ts : dates) {
  149.             final AbsoluteDate date = ts.getDate();
  150.             final boolean notPresentYet = eventDateList.stream().noneMatch(d -> d.getDate().isEqualTo(date));
  151.             if (notPresentYet) {
  152.                 addEventDate(date);
  153.             }
  154.         }
  155.     }

  157.     /**
  158.      * Setup minimum gap between added dates.
  159.      * @param newMinGap new minimum gap between added dates
  160.      * @return a new detector with updated configuration (the instance is not changed)
  161.      * @since 12.0
  162.      */
  163.     public DateDetector withMinGap(final double newMinGap) {
  164.         return new DateDetector(getDetectionSettings(), getHandler(), newMinGap,
  165.                                 eventDateList.toArray(new EventDate[0]));
  166.     }

  168.     /** {@inheritDoc} */
  169.     @Override
  170.     protected DateDetector create(final EventDetectionSettings detectionSettings, final EventHandler newHandler) {
  171.         return new DateDetector(detectionSettings, newHandler, minGap,
  172.                                 eventDateList.toArray(new EventDate[0]));
  173.     }

  175.     /** Get all event dates currently managed, in chronological order.
  176.      * @return all event dates currently managed, in chronological order
  177.      * @since 11.1
  178.      */
  179.     public List<TimeStamped> getDates() {
  180.         return Collections.unmodifiableList(eventDateList);
  181.     }

  183.     /** Compute the value of the switching function.
  184.      * This function measures the difference between the current and the target date.
  185.      * @param s the current state information: date, kinematics, attitude
  186.      * @return value of the switching function
  187.      */
  188.     public double g(final SpacecraftState s) {
  189.         gDate = s.getDate();
  190.         if (currentIndex < 0) {
  191.             return -1.0;
  192.         } else {
  193.             final EventDate event = getClosest(gDate);
  194.             return event.isgIncrease() ? gDate.durationFrom(event.getDate()) : event.getDate().durationFrom(gDate);
  195.         }
  196.     }

  198.     /** Get the current event date according to the propagator.
  199.      * @return event date
  200.      */
  201.     public AbsoluteDate getDate() {
  202.         return currentIndex < 0 ? null : eventDateList.get(currentIndex).getDate();
  203.     }

  205.     /** Get the minimum gap between added dates.
  206.      * @return the minimum gap between added dates (s)
  207.      */
  208.     public double getMinGap() {
  209.         return minGap;
  210.     }

  212.     /** Add an event date.
  213.      * <p>The date to add must be:</p>
  214.      * <ul>
  215.      *   <li>less than the smallest already registered event date minus the maxCheck</li>
  216.      *   <li>or more than the largest already registered event date plus the maxCheck</li>
  217.      * </ul>
  218.      * @param target target date
  219.      * @throws IllegalArgumentException if the date is too close from already defined interval
  220.      * @see #DateDetector(TimeStamped...)
  221.      */
  222.     public void addEventDate(final AbsoluteDate target) throws IllegalArgumentException {
  223.         final boolean increasing;
  224.         if (currentIndex < 0) {
  225.             increasing = (gDate == null) ? true : target.durationFrom(gDate) > 0.0;
  226.             currentIndex = 0;
  227.             eventDateList.add(new EventDate(target, increasing));
  228.         } else {
  229.             final int          lastIndex = eventDateList.size() - 1;
  230.             final AbsoluteDate firstDate = eventDateList.get(0).getDate();
  231.             final AbsoluteDate lastDate  = eventDateList.get(lastIndex).getDate();
  232.             if (firstDate.durationFrom(target) > minGap) {
  233.                 increasing = !eventDateList.get(0).isgIncrease();
  234.                 eventDateList.add(0, new EventDate(target, increasing));
  235.                 currentIndex++;
  236.             } else if (target.durationFrom(lastDate) > minGap) {
  237.                 increasing = !eventDateList.get(lastIndex).isgIncrease();
  238.                 eventDateList.add(new EventDate(target, increasing));
  239.             } else {
  240.                 throw new OrekitIllegalArgumentException(OrekitMessages.EVENT_DATE_TOO_CLOSE,
  241.                                                          target,
  242.                                                          firstDate,
  243.                                                          lastDate,
  244.                                                          minGap,
  245.                                                          firstDate.durationFrom(target),
  246.                                                          target.durationFrom(lastDate));
  247.             }
  248.         }
  249.     }

  251.     /** Get the closest EventDate to the target date.
  252.      * @param target target date
  253.      * @return current EventDate
  254.      */
  255.     private EventDate getClosest(final AbsoluteDate target) {
  256.         final double dt = target.durationFrom(eventDateList.get(currentIndex).getDate());
  257.         if (dt < 0.0 && currentIndex > 0) {
  258.             boolean found = false;
  259.             while (currentIndex > 0 && !found) {
  260.                 if (target.durationFrom(eventDateList.get(currentIndex - 1).getDate()) < eventDateList.get(currentIndex).getDate().durationFrom(target)) {
  261.                     currentIndex--;
  262.                 } else {
  263.                     found = true;
  264.                 }
  265.             }
  266.         } else if (dt > 0.0 && currentIndex < eventDateList.size() - 1) {
  267.             final int maxIndex = eventDateList.size() - 1;
  268.             boolean found = false;
  269.             while (currentIndex < maxIndex && !found) {
  270.                 if (target.durationFrom(eventDateList.get(currentIndex + 1).getDate()) > eventDateList.get(currentIndex).getDate().durationFrom(target)) {
  271.                     currentIndex++;
  272.                 } else {
  273.                     found = true;
  274.                 }
  275.             }
  276.         }
  277.         return eventDateList.get(currentIndex);
  278.     }

  280.     /** Event date specification. */
  281.     private static class EventDate implements TimeStamped {

  283.         /** Event date. */
  284.         private final AbsoluteDate eventDate;

  286.         /** Flag for g function way around event date. */
  287.         private final boolean gIncrease;

  289.         /** Simple constructor.
  290.          * @param date date
  291.          * @param increase if true, g function increases around event date
  292.          */
  293.         EventDate(final AbsoluteDate date, final boolean increase) {
  294.             this.eventDate = date;
  295.             this.gIncrease = increase;
  296.         }

  298.         /** Getter for event date.
  299.          * @return event date
  300.          */
  301.         public AbsoluteDate getDate() {
  302.             return eventDate;
  303.         }

  305.         /** Getter for g function way at event date.
  306.          * @return g function increasing flag
  307.          */
  308.         public boolean isgIncrease() {
  309.             return gIncrease;
  310.         }

  312.     }

  314. }
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