1   /* Copyright 2002-2025 CS GROUP
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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
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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
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17  package org.orekit.propagation.analytical;
18  
19  import java.util.Collections;
20  import java.util.List;
21  
22  import org.hipparchus.analysis.differentiation.Gradient;
23  import org.orekit.attitudes.AttitudeProvider;
24  import org.orekit.propagation.FieldSpacecraftState;
25  import org.orekit.utils.ParameterDriver;
26  
27  /**
28   * Converter for Eckstein-Hechler propagator.
29   *
30   * @author Bryan Cazabonne
31   * @since 11.1
32   */
33  class EcksteinHechlerGradientConverter extends AbstractAnalyticalGradientConverter {
34  
35      /** Fixed dimension of the state. */
36      public static final int FREE_STATE_PARAMETERS = 6;
37  
38      /** Orbit propagator. */
39      private final EcksteinHechlerPropagator propagator;
40  
41      /** Simple constructor.
42       * @param propagator orbit propagator used to access initial orbit
43       */
44      EcksteinHechlerGradientConverter(final EcksteinHechlerPropagator propagator) {
45          super(propagator, FREE_STATE_PARAMETERS);
46          // Initialize fields
47          this.propagator = propagator;
48      }
49  
50      /** {@inheritDoc} */
51      @Override
52      public FieldEcksteinHechlerPropagator<Gradient> getPropagator() {
53  
54          final FieldSpacecraftState<Gradient> state = getState(this);
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.getOrbit().getA().newInstance(propagator.getMu());
63  
64          // Return the "Field" propagator
65          return new FieldEcksteinHechlerPropagator<>(state.getOrbit(), provider, radius, mu,
66                                                      ck0[2], ck0[3], ck0[4], ck0[5], ck0[6]);
67  
68      }
69  
70      /** {@inheritDoc} */
71      @Override
72      public List<ParameterDriver> getParametersDrivers() {
73          return Collections.emptyList();
74      }
75  
76  }