EclipseDetector.java

  1. /* Copyright 2002-2019 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 org.hipparchus.geometry.euclidean.threed.Vector3D;
  20. import org.hipparchus.util.FastMath;
  21. import org.orekit.propagation.SpacecraftState;
  22. import org.orekit.propagation.events.handlers.EventHandler;
  23. import org.orekit.propagation.events.handlers.StopOnIncreasing;
  24. import org.orekit.utils.PVCoordinatesProvider;

  26. /** Finder for satellite eclipse related events.
  27.  * <p>This class finds eclipse events, i.e. satellite within umbra (total
  28.  * eclipse) or penumbra (partial eclipse).</p>
  29.  * <p>The default implementation behavior is to {@link
  30.  * org.orekit.propagation.events.handlers.EventHandler.Action#CONTINUE continue}
  31.  * propagation when entering the eclipse and to {@link
  32.  * org.orekit.propagation.events.handlers.EventHandler.Action#STOP stop} propagation
  33.  * when exiting the eclipse. This can be changed by calling {@link
  34.  * #withHandler(EventHandler)} after construction.</p>
  35.  * @see org.orekit.propagation.Propagator#addEventDetector(EventDetector)
  36.  * @author Pascal Parraud
  37.  */
  38. public class EclipseDetector extends AbstractDetector<EclipseDetector> {

  40.     /** Serializable UID. */
  41.     private static final long serialVersionUID = 20131118L;

  43.     /** Occulting body. */
  44.     private final PVCoordinatesProvider occulting;

  46.     /** Occulting body radius (m). */
  47.     private final double occultingRadius;

  49.     /** Occulted body. */
  50.     private final PVCoordinatesProvider occulted;

  52.     /** Occulted body radius (m). */
  53.     private final double occultedRadius;

  55.     /** Umbra, if true, or penumbra, if false, detection flag. */
  56.     private final boolean totalEclipse;

  58.     /** Build a new eclipse detector.
  59.      * <p>The new instance is a total eclipse (umbra) detector with default
  60.      * values for maximal checking interval ({@link #DEFAULT_MAXCHECK})
  61.      * and convergence threshold ({@link #DEFAULT_THRESHOLD}).</p>
  62.      * @param occulted the body to be occulted
  63.      * @param occultedRadius the radius of the body to be occulted (m)
  64.      * @param occulting the occulting body
  65.      * @param occultingRadius the occulting body radius (m)
  66.      */
  67.     public EclipseDetector(final PVCoordinatesProvider occulted,  final double occultedRadius,
  68.                            final PVCoordinatesProvider occulting, final double occultingRadius) {
  69.         this(DEFAULT_MAXCHECK, DEFAULT_THRESHOLD,
  70.              occulted, occultedRadius, occulting, occultingRadius);
  71.     }

  73.     /** Build a new eclipse detector.
  74.      * <p>The new instance is a total eclipse (umbra) detector with default
  75.      * value for convergence threshold ({@link #DEFAULT_THRESHOLD}).</p>
  76.      * <p>The maximal interval between eclipse checks should be smaller than
  77.      * the half duration of the minimal pass to handle, otherwise some short
  78.      * passes could be missed.</p>
  79.      * @param maxCheck maximal checking interval (s)
  80.      * @param occulted the body to be occulted
  81.      * @param occultedRadius the radius of the body to be occulted in meters
  82.      * @param occulting the occulting body
  83.      * @param occultingRadius the occulting body radius in meters
  84.      */
  85.     public EclipseDetector(final double maxCheck,
  86.                            final PVCoordinatesProvider occulted,  final double occultedRadius,
  87.                            final PVCoordinatesProvider occulting, final double occultingRadius) {
  88.         this(maxCheck, DEFAULT_THRESHOLD,
  89.              occulted, occultedRadius, occulting, occultingRadius);
  90.     }

  92.     /** Build a new eclipse detector.
  93.      * <p>The new instance is a total eclipse (umbra) detector.</p>
  94.      * <p>The maximal interval between eclipse checks should be smaller than
  95.      * the half duration of the minimal pass to handle, otherwise some short
  96.      * passes could be missed.</p>
  97.      * @param maxCheck maximal checking interval (s)
  98.      * @param threshold convergence threshold (s)
  99.      * @param occulted the body to be occulted
  100.      * @param occultedRadius the radius of the body to be occulted in meters
  101.      * @param occulting the occulting body
  102.      * @param occultingRadius the occulting body radius in meters
  103.      */
  104.     public EclipseDetector(final double maxCheck, final double threshold,
  105.                            final PVCoordinatesProvider occulted,  final double occultedRadius,
  106.                            final PVCoordinatesProvider occulting, final double occultingRadius) {
  107.         this(maxCheck, threshold, DEFAULT_MAX_ITER, new StopOnIncreasing<EclipseDetector>(),
  108.              occulted, occultedRadius, occulting, occultingRadius, true);
  109.     }

  111.     /** Private constructor with full parameters.
  112.      * <p>
  113.      * This constructor is private as users are expected to use the builder
  114.      * API with the various {@code withXxx()} methods to set up the instance
  115.      * in a readable manner without using a huge amount of parameters.
  116.      * </p>
  117.      * @param maxCheck maximum checking interval (s)
  118.      * @param threshold convergence threshold (s)
  119.      * @param maxIter maximum number of iterations in the event time search
  120.      * @param handler event handler to call at event occurrences
  121.      * @param occulted the body to be occulted
  122.      * @param occultedRadius the radius of the body to be occulted in meters
  123.      * @param occulting the occulting body
  124.      * @param occultingRadius the occulting body radius in meters
  125.      * @param totalEclipse umbra (true) or penumbra (false) detection flag
  126.      * @since 6.1
  127.      */
  128.     private EclipseDetector(final double maxCheck, final double threshold,
  129.                             final int maxIter, final EventHandler<? super EclipseDetector> handler,
  130.                             final PVCoordinatesProvider occulted,  final double occultedRadius,
  131.                             final PVCoordinatesProvider occulting, final double occultingRadius,
  132.                             final boolean totalEclipse) {
  133.         super(maxCheck, threshold, maxIter, handler);
  134.         this.occulted        = occulted;
  135.         this.occultedRadius  = FastMath.abs(occultedRadius);
  136.         this.occulting       = occulting;
  137.         this.occultingRadius = FastMath.abs(occultingRadius);
  138.         this.totalEclipse    = totalEclipse;
  139.     }

  141.     /** {@inheritDoc} */
  142.     @Override
  143.     protected EclipseDetector create(final double newMaxCheck, final double newThreshold,
  144.                                      final int nawMaxIter, final EventHandler<? super EclipseDetector> newHandler) {
  145.         return new EclipseDetector(newMaxCheck, newThreshold, nawMaxIter, newHandler,
  146.                                    occulted, occultedRadius, occulting, occultingRadius, totalEclipse);
  147.     }

  149.     /**
  150.      * Setup the detector to full umbra detection.
  151.      * <p>
  152.      * This will override a penumbra/umbra flag if it has been configured previously.
  153.      * </p>
  154.      * @return a new detector with updated configuration (the instance is not changed)
  155.      * @see #withPenumbra()
  156.      * @since 6.1
  157.      */
  158.     public EclipseDetector withUmbra() {
  159.         return new EclipseDetector(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(), getHandler(),
  160.                                    occulted, occultedRadius, occulting, occultingRadius,
  161.                                    true);
  162.     }

  164.     /**
  165.      * Setup the detector to penumbra detection.
  166.      * <p>
  167.      * This will override a penumbra/umbra flag if it has been configured previously.
  168.      * </p>
  169.      * @return a new detector with updated configuration (the instance is not changed)
  170.      * @see #withUmbra()
  171.      * @since 6.1
  172.      */
  173.     public EclipseDetector withPenumbra() {
  174.         return new EclipseDetector(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(), getHandler(),
  175.                                    occulted, occultedRadius, occulting, occultingRadius,
  176.                                    false);
  177.     }

  179.     /** Get the occulting body.
  180.      * @return the occulting body
  181.      */
  182.     public PVCoordinatesProvider getOcculting() {
  183.         return occulting;
  184.     }

  186.     /** Get the occulting body radius (m).
  187.      * @return the occulting body radius
  188.      */
  189.     public double getOccultingRadius() {
  190.         return occultingRadius;
  191.     }

  193.     /** Get the occulted body.
  194.      * @return the occulted body
  195.      */
  196.     public PVCoordinatesProvider getOcculted() {
  197.         return occulted;
  198.     }

  200.     /** Get the occulted body radius (m).
  201.      * @return the occulted body radius
  202.      */
  203.     public double getOccultedRadius() {
  204.         return occultedRadius;
  205.     }

  207.     /** Get the total eclipse detection flag.
  208.      * @return the total eclipse detection flag (true for umbra events detection,
  209.      * false for penumbra events detection)
  210.      */
  211.     public boolean getTotalEclipse() {
  212.         return totalEclipse;
  213.     }

  215.     /** Compute the value of the switching function.
  216.      * This function becomes negative when entering the region of shadow
  217.      * and positive when exiting.
  218.      * @param s the current state information: date, kinematics, attitude
  219.      * @return value of the switching function
  220.      */
  221.     public double g(final SpacecraftState s) {
  222.         final Vector3D pted = occulted.getPVCoordinates(s.getDate(), s.getFrame()).getPosition();
  223.         final Vector3D ping = occulting.getPVCoordinates(s.getDate(), s.getFrame()).getPosition();
  224.         final Vector3D psat = s.getPVCoordinates().getPosition();
  225.         final Vector3D ps   = pted.subtract(psat);
  226.         final Vector3D po   = ping.subtract(psat);
  227.         final double angle  = Vector3D.angle(ps, po);
  228.         final double rs     = FastMath.asin(occultedRadius / ps.getNorm());
  229.         if (Double.isNaN(rs)) {
  230.             return FastMath.PI;
  231.         }
  232.         final double ro     = FastMath.asin(occultingRadius / po.getNorm());
  233.         if (Double.isNaN(ro)) {
  234.             return -FastMath.PI;
  235.         }
  236.         return totalEclipse ? (angle - ro + rs) : (angle - ro - rs);
  237.     }

  239. }
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