1   /* Copyright 2022-2025 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.control.indirect.adjoint;
18  
19  import org.hipparchus.CalculusFieldElement;
20  import org.hipparchus.util.MathArrays;
21  import org.orekit.frames.Frame;
22  import org.orekit.time.AbsoluteDate;
23  import org.orekit.time.FieldAbsoluteDate;
24  
25  /**
26   * Abstract class for common computations regarding adjoint dynamics and gravity for Cartesian coordinates.
27   *
28   * @author Romain Serra
29   * @see CartesianAdjointEquationTerm
30   * @since 12.2
31   */
32  public abstract class AbstractCartesianAdjointGravitationalTerm extends AbstractCartesianAdjointEquationTerm {
33  
34      /** Body gravitational parameter. */
35      private final double mu;
36  
37      /**
38       * Constructor.
39       * @param mu body gravitational parameter
40       */
41      protected AbstractCartesianAdjointGravitationalTerm(final double mu) {
42          this.mu = mu;
43      }
44  
45      /**
46       * Getter for the gravitational constant.
47       * @return mu
48       */
49      public double getMu() {
50          return mu;
51      }
52  
53      /** {@inheritDoc} */
54      @Override
55      public double[] getRatesContribution(final AbsoluteDate date, final double[] stateVariables,
56                                           final double[] adjointVariables, final Frame frame) {
57          final double[] contribution = new double[adjointVariables.length];
58          final double[] positionAdjointContribution = getPositionAdjointContribution(date, stateVariables,
59              adjointVariables, frame);
60          System.arraycopy(positionAdjointContribution, 0, contribution, 0, positionAdjointContribution.length);
61          return contribution;
62      }
63  
64      /**
65       * Computes the contribution to position adjoint derivatives.
66       *
67       * @param date             date
68       * @param stateVariables   state variables
69       * @param adjointVariables adjoint variables
70       * @param frame            propagation frame
71       * @return contribution to position adjoint derivatives
72       */
73      protected abstract double[] getPositionAdjointContribution(AbsoluteDate date, double[] stateVariables,
74                                                                 double[] adjointVariables, Frame frame);
75  
76      /** {@inheritDoc} */
77      @Override
78      public <T extends CalculusFieldElement<T>> T[] getFieldRatesContribution(final FieldAbsoluteDate<T> date,
79                                                                               final T[] stateVariables,
80                                                                               final T[] adjointVariables, final Frame frame) {
81          final T[] contribution = MathArrays.buildArray(date.getField(), adjointVariables.length);
82          final T[] positionAdjointFieldContribution = getPositionAdjointFieldContribution(date, stateVariables,
83              adjointVariables, frame);
84          System.arraycopy(positionAdjointFieldContribution, 0, contribution, 0, positionAdjointFieldContribution.length);
85          return contribution;
86      }
87  
88      /**
89       * Computes the contribution to position adjoint derivatives.
90       *
91       * @param <T>              field type
92       * @param date             date
93       * @param stateVariables   state variables
94       * @param adjointVariables adjoint variables
95       * @param frame            propagation frame
96       * @return contribution to position adjoint derivatives
97       */
98      protected abstract <T extends CalculusFieldElement<T>> T[] getPositionAdjointFieldContribution(FieldAbsoluteDate<T> date,
99                                                                                                     T[] stateVariables,
100                                                                                                    T[] adjointVariables,
101                                                                                                    Frame frame);
102 }