DateDetector.java

  1. /* Copyright 2002-2013 CS Systèmes d'Information
  2.  * Licensed to CS Systèmes d'Information (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.io.Serializable;
  20. import java.util.ArrayList;

  22. import org.orekit.errors.OrekitException;
  23. import org.orekit.errors.OrekitMessages;
  24. import org.orekit.propagation.SpacecraftState;
  25. import org.orekit.propagation.events.handlers.EventHandler;
  26. import org.orekit.propagation.events.handlers.StopOnEvent;
  27. import org.orekit.time.AbsoluteDate;
  28. import org.orekit.time.TimeStamped;

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

  48.     /** Serializable UID. */
  49.     private static final long serialVersionUID = 20131118L;

  51.     /** Last date for g computation. */
  52.     private AbsoluteDate gDate;

  54.     /** List of event dates. */
  55.     private final ArrayList<EventDate> eventDateList;

  57.     /** Current event date. */
  58.     private int currentIndex;

  60.     /** Build a new instance.
  61.      * <p>First event dates are set here, but others can be
  62.      * added later with {@link #addEventDate(AbsoluteDate)}.</p>
  63.      * @param maxCheck maximum checking interval (s)
  64.      * @param threshold convergence threshold (s)
  65.      * @param dates list of event dates
  66.      * @see #addEventDate(AbsoluteDate)
  67.      */
  68.     public DateDetector(final double maxCheck, final double threshold, final TimeStamped ... dates) {
  69.         this(maxCheck, threshold, DEFAULT_MAX_ITER, new StopOnEvent<DateDetector>(), dates);
  70.     }

  72.     /** Build a new instance.
  73.      * <p>This constructor is dedicated to single date detection.
  74.      * {@link #getMaxCheckInterval() max check interval} is set to 1.0e10, so almost
  75.      * no other date can be added. Tolerance is set to 1.0e-9.</p>
  76.      * @param target target date
  77.      * @see #addEventDate(AbsoluteDate)
  78.      */
  79.     public DateDetector(final AbsoluteDate target) {
  80.         this(1.0e10, 1.e-9, target);
  81.     }

  83.     /** Private constructor with full parameters.
  84.      * <p>
  85.      * This constructor is private as users are expected to use the builder
  86.      * API with the various {@code withXxx()} methods to set up the instance
  87.      * in a readable manner without using a huge amount of parameters.
  88.      * </p>
  89.      * @param maxCheck maximum checking interval (s)
  90.      * @param threshold convergence threshold (s)
  91.      * @param maxIter maximum number of iterations in the event time search
  92.      * @param handler event handler to call at event occurrences
  93.      * @param dates list of event dates
  94.      * @since 6.1
  95.      */
  96.     private DateDetector(final double maxCheck, final double threshold,
  97.                          final int maxIter, final EventHandler<DateDetector> handler,
  98.                          final TimeStamped ... dates) {
  99.         super(maxCheck, threshold, maxIter, handler);
  100.         this.currentIndex  = -1;
  101.         this.gDate         = null;
  102.         this.eventDateList = new ArrayList<DateDetector.EventDate>(dates.length);
  103.         for (final TimeStamped ts : dates) {
  104.             addEventDate(ts.getDate());
  105.         }
  106.     }

  108.     /** {@inheritDoc} */
  109.     @Override
  110.     protected DateDetector create(final double newMaxCheck, final double newThreshold,
  111.                                   final int newMaxIter, final EventHandler<DateDetector> newHandler) {
  112.         return new DateDetector(newMaxCheck, newThreshold, newMaxIter, newHandler,
  113.                                 eventDateList.toArray(new EventDate[eventDateList.size()]));
  114.     }

  116.     /** Compute the value of the switching function.
  117.      * This function measures the difference between the current and the target date.
  118.      * @param s the current state information: date, kinematics, attitude
  119.      * @return value of the switching function
  120.      * @exception OrekitException if some specific error occurs
  121.      */
  122.     public double g(final SpacecraftState s) throws OrekitException {
  123.         gDate = s.getDate();
  124.         if (currentIndex < 0) {
  125.             return -1.0;
  126.         } else {
  127.             final EventDate event = getClosest(gDate);
  128.             return event.isgIncrease() ? gDate.durationFrom(event.getDate()) : event.getDate().durationFrom(gDate);
  129.         }
  130.     }

  132.     /** Get the current event date according to the propagator.
  133.      * @return event date
  134.      */
  135.     public AbsoluteDate getDate() {
  136.         return currentIndex < 0 ? null : eventDateList.get(currentIndex).getDate();
  137.     }

  139.     /** Add an event date.
  140.      * <p>The date to add must be:</p>
  141.      * <ul>
  142.      *   <li>less than the smallest already registered event date minus the maxCheck</li>
  143.      *   <li>or more than the largest already registered event date plus the maxCheck</li>
  144.      * </ul>
  145.      * @param target target date
  146.      * @throws IllegalArgumentException if the date is too close from already defined interval
  147.      * @see #DateDetector(double, double, TimeStamped...)
  148.      */
  149.     public void addEventDate(final AbsoluteDate target) throws IllegalArgumentException {
  150.         final boolean increasing;
  151.         if (currentIndex < 0) {
  152.             increasing = (gDate == null) ? true : target.durationFrom(gDate) > 0.0;
  153.             currentIndex = 0;
  154.             eventDateList.add(new EventDate(target, increasing));
  155.         } else {
  156.             final int lastIndex = eventDateList.size() - 1;
  157.             if (eventDateList.get(0).getDate().durationFrom(target) > getMaxCheckInterval()) {
  158.                 increasing = !eventDateList.get(0).isgIncrease();
  159.                 eventDateList.add(0, new EventDate(target, increasing));
  160.                 currentIndex++;
  161.             } else if (target.durationFrom(eventDateList.get(lastIndex).getDate()) > getMaxCheckInterval()) {
  162.                 increasing = !eventDateList.get(lastIndex).isgIncrease();
  163.                 eventDateList.add(new EventDate(target, increasing));
  164.             } else {
  165.                 throw OrekitException.createIllegalArgumentException(OrekitMessages.EVENT_DATE_TOO_CLOSE,
  166.                                                                      target,
  167.                                                                      eventDateList.get(0).getDate(),
  168.                                                                      eventDateList.get(lastIndex).getDate(),
  169.                                                                      getMaxCheckInterval());
  170.             }
  171.         }
  172.     }

  174.     /** Get the closest EventDate to the target date.
  175.      * @param target target date
  176.      * @return current EventDate
  177.      */
  178.     private EventDate getClosest(final AbsoluteDate target) {
  179.         final double dt = target.durationFrom(eventDateList.get(currentIndex).getDate());
  180.         if (dt < 0.0 && currentIndex > 0) {
  181.             boolean found = false;
  182.             while (currentIndex > 0 && !found) {
  183.                 if (target.durationFrom(eventDateList.get(currentIndex - 1).getDate()) < eventDateList.get(currentIndex).getDate().durationFrom(target)) {
  184.                     currentIndex--;
  185.                 } else {
  186.                     found = true;
  187.                 }
  188.             }
  189.         } else if (dt > 0.0 && currentIndex < eventDateList.size() - 1) {
  190.             final int maxIndex = eventDateList.size() - 1;
  191.             boolean found = false;
  192.             while (currentIndex < maxIndex && !found) {
  193.                 if (target.durationFrom(eventDateList.get(currentIndex + 1).getDate()) > eventDateList.get(currentIndex).getDate().durationFrom(target)) {
  194.                     currentIndex++;
  195.                 } else {
  196.                     found = true;
  197.                 }
  198.             }
  199.         }
  200.         return eventDateList.get(currentIndex);
  201.     }

  203.     /** Event date specification. */
  204.     private static class EventDate implements Serializable, TimeStamped {

  206.         /** Serializable UID. */
  207.         private static final long serialVersionUID = -7641032576122527149L;

  209.         /** Event date. */
  210.         private final AbsoluteDate eventDate;

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

  215.         /** Simple constructor.
  216.          * @param date date
  217.          * @param increase if true, g function increases around event date
  218.          */
  219.         public EventDate(final AbsoluteDate date, final boolean increase) {
  220.             this.eventDate = date;
  221.             this.gIncrease = increase;
  222.         }

  224.         /** Getter for event date.
  225.          * @return event date
  226.          */
  227.         public AbsoluteDate getDate() {
  228.             return eventDate;
  229.         }

  231.         /** Getter for g function way at event date.
  232.          * @return g function increasing flag
  233.          */
  234.         public boolean isgIncrease() {
  235.             return gIncrease;
  236.         }

  238.     }

  240. }
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