1   /* Copyright 2002-2021 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;
18  
19  import org.hipparchus.CalculusFieldElement;
20  import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
21  import org.hipparchus.ode.events.Action;
22  import org.orekit.orbits.FieldOrbit;
23  import org.orekit.propagation.FieldSpacecraftState;
24  import org.orekit.propagation.events.handlers.FieldEventHandler;
25  import org.orekit.propagation.events.handlers.FieldStopOnIncreasing;
26  import org.orekit.utils.FieldPVCoordinates;
27  
28  /** Finder for apside crossing events.
29   * <p>This class finds apside crossing events (i.e. apogee or perigee crossing).</p>
30   * <p>The default implementation behavior is to {@link Action#CONTINUE continue}
31   * propagation at apogee crossing and to {@link Action#STOP stop} propagation
32   * at perigee crossing. This can be changed by calling
33   * {@link #withHandler(FieldEventHandler)} after construction.</p>
34   * <p>Beware that apside detection will fail for almost circular orbits. If
35   * for example an apside detector is used to trigger an {@link
36   * org.orekit.forces.maneuvers.ImpulseManeuver ImpulseManeuver} and the maneuver
37   * change the orbit shape to circular, then the detector may completely fail just
38   * after the maneuver has been performed!</p>
39   * @see org.orekit.propagation.FieldPropagator#addEventDetector(FieldEventDetector)
40   * @author Luc Maisonobe
41   */
42  public class FieldApsideDetector<T extends CalculusFieldElement<T>> extends FieldAbstractDetector<FieldApsideDetector<T>, T> {
43  
44      /** Build a new instance.
45       * <p>The orbit is used only to set an upper bound for the
46       * max check interval to period/3 and to set the convergence
47       * threshold according to orbit size</p>
48       * @param orbit initial orbit
49       */
50      public FieldApsideDetector(final FieldOrbit<T> orbit) {
51          this(orbit.getKeplerianPeriod().multiply(1.0e-13), orbit);
52      }
53  
54      /** Build a new instance.
55       * <p>The orbit is used only to set an upper bound for the
56       * max check interval to period/3</p>
57       * @param threshold convergence threshold (s)
58       * @param orbit initial orbit
59       */
60      public FieldApsideDetector(final T threshold, final FieldOrbit<T> orbit) {
61          super(orbit.getKeplerianPeriod().divide(3), threshold,
62                DEFAULT_MAX_ITER, new FieldStopOnIncreasing<FieldApsideDetector<T>, T>());
63      }
64  
65      /** Private constructor with full parameters.
66       * <p>
67       * This constructor is private as users are expected to use the builder
68       * API with the various {@code withXxx()} methods to set up the instance
69       * in a readable manner without using a huge amount of parameters.
70       * </p>
71       * @param maxCheck maximum checking interval (s)
72       * @param threshold convergence threshold (s)
73       * @param maxIter maximum number of iterations in the event time search
74       * @param handler event handler to call at event occurrences
75       */
76      private FieldApsideDetector(final T maxCheck, final T threshold,
77                                  final int maxIter, final FieldEventHandler<? super FieldApsideDetector<T>, T> handler) {
78          super(maxCheck, threshold, maxIter, handler);
79      }
80  
81      /** {@inheritDoc} */
82      @Override
83      protected FieldApsideDetector<T> create(final T newMaxCheck, final T newThreshold,
84                                              final int newMaxIter,
85                                              final FieldEventHandler<? super FieldApsideDetector<T>, T> newHandler) {
86          return new FieldApsideDetector<>(newMaxCheck, newThreshold, newMaxIter, newHandler);
87      }
88  
89      /** Compute the value of the switching function.
90       * This function computes the dot product of the 2 vectors : position.velocity.
91       * @param s the current state information: date, kinematics, attitude
92       * @return value of the switching function
93       */
94      public T g(final FieldSpacecraftState<T> s) {
95          final FieldPVCoordinates<T> pv = s.getPVCoordinates();
96          return FieldVector3D.dotProduct(pv.getPosition(), pv.getVelocity());
97      }
98  
99  }