1   /* Copyright 2022-2026 Romain Serra
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.functions;
18  
19  import org.hipparchus.CalculusFieldElement;
20  import org.orekit.propagation.FieldSpacecraftState;
21  import org.orekit.propagation.SpacecraftState;
22  import org.orekit.utils.OccultationEngine;
23  
24  /**
25   * Class for penumbra event with conical shadows from ellipsoidal occulting bodies.
26   * It is negative in penumbra, positive otherwise.
27   * @author Romain Serra
28   * @see OccultationEngine
29   * @since 14.0
30   */
31  public class PenumbraEventFunction implements EventFunction {
32  
33      /** Occultation engine. */
34      private final OccultationEngine occultationEngine;
35  
36      /**
37       * Constructor.
38       * @param occultationEngine occultation engine
39       */
40      public PenumbraEventFunction(final OccultationEngine occultationEngine) {
41          this.occultationEngine = occultationEngine;
42      }
43  
44      @Override
45      public double value(final SpacecraftState state) {
46          final OccultationEngine.OccultationAngles angles = occultationEngine.angles(state);
47          return angles.getSeparation() - angles.getLimbRadius() - angles.getOccultedApparentRadius();
48      }
49  
50      @Override
51      public <T extends CalculusFieldElement<T>> T value(final FieldSpacecraftState<T> fieldState) {
52          final OccultationEngine.FieldOccultationAngles<T> angles = occultationEngine.angles(fieldState);
53          return angles.getSeparation().subtract(angles.getLimbRadius()).subtract(angles.getOccultedApparentRadius());
54      }
55  }