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3    * contributor license agreements.  See the NOTICE file distributed with
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5    * CS licenses this file to You under the Apache License, Version 2.0
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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.
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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   * @param <T> type of the field elements
42   */
43  public class FieldApsideDetector<T extends CalculusFieldElement<T>> extends FieldAbstractDetector<FieldApsideDetector<T>, T> {
44  
45      /** Build a new instance.
46       * <p>The Keplerian period is used only to set an upper bound for the
47       * max check interval to period/3 and to set the convergence threshold.</p>
48       * @param keplerianPeriod estimate of the Keplerian period
49       * @since 12.1
50       */
51      public FieldApsideDetector(final T keplerianPeriod) {
52          super(FieldAdaptableInterval.of(keplerianPeriod.divide(3).getReal()), keplerianPeriod.multiply(1e-13),
53              DEFAULT_MAX_ITER, new FieldStopOnIncreasing<>());
54      }
55  
56      /** Build a new instance.
57       * <p>The orbit is used only to set an upper bound for the
58       * max check interval to period/3 and to set the convergence
59       * threshold according to orbit size</p>
60       * @param orbit initial orbit
61       */
62      public FieldApsideDetector(final FieldOrbit<T> orbit) {
63          this(orbit.getKeplerianPeriod());
64      }
65  
66      /** Build a new instance.
67       * <p>The orbit is used only to set an upper bound for the
68       * max check interval to period/3</p>
69       * @param threshold convergence threshold (s)
70       * @param orbit initial orbit
71       */
72      public FieldApsideDetector(final T threshold, final FieldOrbit<T> orbit) {
73          super(FieldAdaptableInterval.of(orbit.getKeplerianPeriod().divide(3).getReal()), threshold,
74                DEFAULT_MAX_ITER, new FieldStopOnIncreasing<>());
75      }
76  
77      /** Protected constructor with full parameters.
78       * <p>
79       * This constructor is public because otherwise all accessible ones would require an orbit.
80       * </p>
81       * @param maxCheck maximum checking interval
82       * @param threshold convergence threshold (s)
83       * @param maxIter maximum number of iterations in the event time search
84       * @param handler event handler to call at event occurrences
85       */
86      public FieldApsideDetector(final FieldAdaptableInterval<T> maxCheck, final T threshold,
87                                 final int maxIter, final FieldEventHandler<T> handler) {
88          super(maxCheck, threshold, maxIter, handler);
89      }
90  
91      /** {@inheritDoc} */
92      @Override
93      protected FieldApsideDetector<T> create(final FieldAdaptableInterval<T> newMaxCheck, final T newThreshold,
94                                              final int newMaxIter,
95                                              final FieldEventHandler<T> newHandler) {
96          return new FieldApsideDetector<>(newMaxCheck, newThreshold, newMaxIter, newHandler);
97      }
98  
99      /** Compute the value of the switching function.
100      * This function computes the dot product of the 2 vectors : position.velocity.
101      * @param s the current state information: date, kinematics, attitude
102      * @return value of the switching function
103      */
104     public T g(final FieldSpacecraftState<T> s) {
105         final FieldPVCoordinates<T> pv = s.getPVCoordinates();
106         return FieldVector3D.dotProduct(pv.getPosition(), pv.getVelocity());
107     }
108 
109 }