FieldEclipseDetector.java

  1. /* Copyright 2002-2018 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.Field;
  20. import org.hipparchus.RealFieldElement;
  21. import org.hipparchus.geometry.euclidean.threed.Vector3D;
  22. import org.hipparchus.util.FastMath;
  23. import org.orekit.errors.OrekitException;
  24. import org.orekit.propagation.FieldSpacecraftState;
  25. import org.orekit.propagation.events.handlers.FieldEventHandler;
  26. import org.orekit.propagation.events.handlers.FieldStopOnIncreasing;
  27. import org.orekit.utils.PVCoordinatesProvider;

  29. /** Finder for satellite eclipse related events.
  30.  * <p>This class finds eclipse events, i.e. satellite within umbra (total
  31.  * eclipse) or penumbra (partial eclipse).</p>
  32.  * <p>The default implementation behavior is to {@link
  33.  * org.orekit.propagation.events.handlers.FieldEventHandler.Action#CONTINUE continue}
  34.  * propagation when entering the eclipse and to {@link
  35.  * org.orekit.propagation.events.handlers.FieldEventHandler.Action#STOP stop} propagation
  36.  * when exiting the eclipse. This can be changed by calling {@link
  37.  * #withHandler(FieldEventHandler)} after construction.</p>
  38.  * @see org.orekit.propagation.FieldPropagator#addEventDetector(FieldEventDetector)
  39.  * @author Pascal Parraud
  40.  */
  41. public class FieldEclipseDetector<T extends RealFieldElement<T>> extends FieldAbstractDetector<FieldEclipseDetector<T>, T> {


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

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

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

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

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

  59.     /** Build a new eclipse detector.
  60.      * <p>The new instance is a total eclipse (umbra) detector with default
  61.      * values for maximal checking interval ({@link #DEFAULT_MAXCHECK})
  62.      * and convergence threshold ({@link #DEFAULT_THRESHOLD}).</p>
  63.      * @param occulted the body to be occulted
  64.      * @param occultedRadius the radius of the body to be occulted (m)
  65.      * @param occulting the occulting body
  66.      * @param occultingRadius the occulting body radius (m)
  67.      * @param field field used by default
  68.      */
  69.     public FieldEclipseDetector(final PVCoordinatesProvider occulted,  final double occultedRadius,
  70.                            final PVCoordinatesProvider occulting, final double occultingRadius, final Field<T> field) {
  71.         this(field.getZero().add(DEFAULT_MAXCHECK), field.getZero().add(DEFAULT_THRESHOLD),
  72.              occulted, occultedRadius, occulting, occultingRadius);
  73.     }

  75.     /** Build a new eclipse detector.
  76.      * <p>The new instance is a total eclipse (umbra) detector with default
  77.      * value for convergence threshold ({@link #DEFAULT_THRESHOLD}).</p>
  78.      * <p>The maximal interval between eclipse checks should be smaller than
  79.      * the half duration of the minimal pass to handle, otherwise some short
  80.      * passes could be missed.</p>
  81.      * @param maxCheck maximal checking interval (s)
  82.      * @param occulted the body to be occulted
  83.      * @param occultedRadius the radius of the body to be occulted in meters
  84.      * @param occulting the occulting body
  85.      * @param occultingRadius the occulting body radius in meters
  86.      */
  87.     public FieldEclipseDetector(final T maxCheck,
  88.                            final PVCoordinatesProvider occulted,  final double occultedRadius,
  89.                            final PVCoordinatesProvider occulting, final double occultingRadius) {
  90.         this(maxCheck, maxCheck.getField().getZero().add(DEFAULT_THRESHOLD),
  91.              occulted, occultedRadius, occulting, occultingRadius);
  92.     }

  94.     /** Build a new eclipse detector.
  95.      * <p>The new instance is a total eclipse (umbra) detector.</p>
  96.      * <p>The maximal interval between eclipse checks should be smaller than
  97.      * the half duration of the minimal pass to handle, otherwise some short
  98.      * passes could be missed.</p>
  99.      * @param maxCheck maximal checking interval (s)
  100.      * @param threshold convergence threshold (s)
  101.      * @param occulted the body to be occulted
  102.      * @param occultedRadius the radius of the body to be occulted in meters
  103.      * @param occulting the occulting body
  104.      * @param occultingRadius the occulting body radius in meters
  105.      */
  106.     public FieldEclipseDetector(final T maxCheck, final T threshold,
  107.                            final PVCoordinatesProvider occulted,  final double occultedRadius,
  108.                            final PVCoordinatesProvider occulting, final double occultingRadius) {
  109.         this(maxCheck, threshold, DEFAULT_MAX_ITER, new FieldStopOnIncreasing<FieldEclipseDetector<T>, T>(),
  110.              occulted, occultedRadius, occulting, occultingRadius, true);
  111.     }

  113.     /** Private constructor with full parameters.
  114.      * <p>
  115.      * This constructor is private as users are expected to use the builder
  116.      * API with the various {@code withXxx()} methods to set up the instance
  117.      * in a readable manner without using a huge amount of parameters.
  118.      * </p>
  119.      * @param maxCheck maximum checking interval (s)
  120.      * @param threshold convergence threshold (s)
  121.      * @param maxIter maximum number of iterations in the event time search
  122.      * @param handler event handler to call at event occurrences
  123.      * @param occulted the body to be occulted
  124.      * @param occultedRadius the radius of the body to be occulted in meters
  125.      * @param occulting the occulting body
  126.      * @param occultingRadius the occulting body radius in meters
  127.      * @param totalEclipse umbra (true) or penumbra (false) detection flag
  128.      * @since 6.1
  129.      */
  130.     private FieldEclipseDetector(final T maxCheck, final T threshold,
  131.                             final int maxIter, final FieldEventHandler<? super FieldEclipseDetector<T>, T> handler,
  132.                             final PVCoordinatesProvider occulted,  final double occultedRadius,
  133.                             final PVCoordinatesProvider occulting, final double occultingRadius,
  134.                             final boolean totalEclipse) {
  135.         super(maxCheck, threshold, maxIter, handler);
  136.         this.occulted        = occulted;
  137.         this.occultedRadius  = FastMath.abs(occultedRadius);
  138.         this.occulting       = occulting;
  139.         this.occultingRadius = FastMath.abs(occultingRadius);
  140.         this.totalEclipse    = totalEclipse;
  141.     }

  143.     /** {@inheritDoc} */
  144.     @Override
  145.     protected FieldEclipseDetector<T> create(final T newMaxCheck, final T newThreshold,
  146.                                      final int nawMaxIter, final FieldEventHandler<? super FieldEclipseDetector<T>, T> newHandler) {
  147.         return new FieldEclipseDetector<>(newMaxCheck, newThreshold, nawMaxIter, newHandler,
  148.                                           occulted, occultedRadius, occulting, occultingRadius, totalEclipse);
  149.     }

  151.     /**
  152.      * Setup the detector to full umbra detection.
  153.      * <p>
  154.      * This will override a penumbra/umbra flag if it has been configured previously.
  155.      * </p>
  156.      * @return a new detector with updated configuration (the instance is not changed)
  157.      * @see #withPenumbra()
  158.      * @since 6.1
  159.      */
  160.     public FieldEclipseDetector<T> withUmbra() {
  161.         return new FieldEclipseDetector<>(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(), getHandler(),
  162.                                           occulted, occultedRadius, occulting, occultingRadius,
  163.                                           true);
  164.     }

  166.     /**
  167.      * Setup the detector to penumbra detection.
  168.      * <p>
  169.      * This will override a penumbra/umbra flag if it has been configured previously.
  170.      * </p>
  171.      * @return a new detector with updated configuration (the instance is not changed)
  172.      * @see #withUmbra()
  173.      * @since 6.1
  174.      */
  175.     public FieldEclipseDetector<T> withPenumbra() {
  176.         return new FieldEclipseDetector<>(getMaxCheckInterval(), getThreshold(), getMaxIterationCount(), getHandler(),
  177.                                           occulted, occultedRadius, occulting, occultingRadius,
  178.                                           false);
  179.     }

  181.     /** Get the occulting body.
  182.      * @return the occulting body
  183.      */
  184.     public PVCoordinatesProvider getOcculting() {
  185.         return occulting;
  186.     }

  188.     /** Get the occulting body radius (m).
  189.      * @return the occulting body radius
  190.      */
  191.     public double getOccultingRadius() {
  192.         return occultingRadius;
  193.     }

  195.     /** Get the occulted body.
  196.      * @return the occulted body
  197.      */
  198.     public PVCoordinatesProvider getOcculted() {
  199.         return occulted;
  200.     }

  202.     /** Get the occulted body radius (m).
  203.      * @return the occulted body radius
  204.      */
  205.     public double getOccultedRadius() {
  206.         return occultedRadius;
  207.     }

  209.     /** Get the total eclipse detection flag.
  210.      * @return the total eclipse detection flag (true for umbra events detection,
  211.      * false for penumbra events detection)
  212.      */
  213.     public boolean getTotalEclipse() {
  214.         return totalEclipse;
  215.     }

  217.     /** Compute the value of the switching function.
  218.      * This function becomes negative when entering the region of shadow
  219.      * and positive when exiting.
  220.      * @param s the current state information: date, kinematics, attitude
  221.      * @return value of the switching function
  222.      * @exception OrekitException if some specific error occurs
  223.      */
  224.     public T g(final FieldSpacecraftState<T> s) throws OrekitException {
  225.         final Vector3D pted = occulted.getPVCoordinates(s.getDate().toAbsoluteDate(), s.getFrame()).getPosition();
  226.         final Vector3D ping = occulting.getPVCoordinates(s.getDate().toAbsoluteDate(), s.getFrame()).getPosition();
  227.         final Vector3D psat = s.toSpacecraftState().getPVCoordinates().getPosition();
  228.         final Vector3D ps   = pted.subtract(psat);
  229.         final Vector3D po   = ping.subtract(psat);
  230.         final double angle  = Vector3D.angle(ps, po);
  231.         final double rs     = FastMath.asin(occultedRadius / ps.getNorm());
  232.         if (Double.isNaN(rs)) {
  233.             return s.getOrbit().getA().getField().getZero().add(FastMath.PI);
  234.         }
  235.         final double ro     = FastMath.asin(occultingRadius / po.getNorm());
  236.         if (Double.isNaN(ro)) {
  237.             return s.getOrbit().getA().getField().getZero().add(-FastMath.PI);
  238.         }
  239.         return totalEclipse ? (s.getOrbit().getA().getField().getZero().add(angle - ro + rs)) :
  240.                               (s.getOrbit().getA().getField().getZero().add(angle - ro - rs));
  241.     }

  243. }
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