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.frames.Frame;
21  import org.orekit.propagation.FieldSpacecraftState;
22  import org.orekit.propagation.SpacecraftState;
23  
24  /** Node crossing event function.
25   * It computes the Z position in the reference frame.
26   * @author Romain Serra
27   * @since 14.0
28   */
29  public class NodeEventFunction implements EventFunction {
30  
31      /** Reference frame. */
32      private final Frame frame;
33  
34      /**
35       * Constructor.
36       * @param frame reference frame for node definition
37       */
38      public NodeEventFunction(final Frame frame) {
39          this.frame = frame;
40      }
41  
42      @Override
43      public double value(final SpacecraftState state) {
44          return state.getPosition(frame).getZ();
45      }
46  
47      @Override
48      public <T extends CalculusFieldElement<T>> T value(final FieldSpacecraftState<T> fieldState) {
49          return fieldState.getPosition(frame).getZ();
50      }
51  
52      /**
53       * Getter for the frame.
54       * @return frame
55       */
56      public Frame getFrame() {
57          return frame;
58      }
59  }