1   /* Copyright 2002-2025 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.analytical;
18  
19  import org.hipparchus.analysis.differentiation.Gradient;
20  import org.orekit.attitudes.AttitudeProvider;
21  import org.orekit.propagation.FieldSpacecraftState;
22  import org.orekit.utils.ParameterDriver;
23  
24  import java.util.List;
25  
26  /**
27   * Converter for Brouwer-Lyddane propagator.
28   *
29   * @author Bryan Cazabonne
30   * @since 11.1
31   */
32  class BrouwerLyddaneGradientConverter extends AbstractAnalyticalGradientConverter {
33  
34      /** Fixed dimension of the state. */
35      public static final int FREE_STATE_PARAMETERS = 6;
36  
37      /** Orbit propagator. */
38      private final BrouwerLyddanePropagator propagator;
39  
40      /** Simple constructor.
41       * @param propagator orbit propagator used to access initial orbit
42       */
43      BrouwerLyddaneGradientConverter(final BrouwerLyddanePropagator propagator) {
44          super(propagator, FREE_STATE_PARAMETERS);
45          // Initialize fields
46          this.propagator = propagator;
47      }
48  
49      /** {@inheritDoc} */
50      @Override
51      public FieldBrouwerLyddanePropagator<Gradient> getPropagator() {
52  
53          final FieldSpacecraftState<Gradient> state = getState(this);
54          final Gradient[] parameters = getParameters(state, propagator);
55  
56          // Model parameters
57          final double[]         ck0      = propagator.getCk0();
58          final double           radius   = propagator.getReferenceRadius();
59          final AttitudeProvider provider = propagator.getAttitudeProvider();
60  
61          // Central attraction coefficient
62          final Gradient mu = state.getMass().newInstance(propagator.getMu());
63  
64          // Return the "Field" propagator
65          return new FieldBrouwerLyddanePropagator<>(state.getOrbit(), provider, radius, mu,
66                                                     ck0[2], ck0[3], ck0[4], ck0[5],
67                                                     parameters[0].getValue());
68  
69      }
70  
71      /** {@inheritDoc} */
72      @Override
73      public List<ParameterDriver> getParametersDrivers() {
74          return propagator.getParametersDrivers();
75      }
76  
77  }