1   /* Copyright 2002-2024 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.semianalytical.dsst;
18  
19  import org.hipparchus.analysis.differentiation.Gradient;
20  import org.orekit.attitudes.AttitudeProvider;
21  import org.orekit.attitudes.FieldAttitude;
22  import org.orekit.orbits.FieldEquinoctialOrbit;
23  import org.orekit.orbits.FieldOrbit;
24  import org.orekit.orbits.PositionAngleType;
25  import org.orekit.propagation.FieldSpacecraftState;
26  import org.orekit.propagation.SpacecraftState;
27  import org.orekit.propagation.integration.AbstractGradientConverter;
28  import org.orekit.time.AbsoluteDate;
29  import org.orekit.time.FieldAbsoluteDate;
30  
31  /** Converter for states and parameters arrays.
32   * @author Luc Maisonobe
33   * @author Bryan Cazabonne
34   * @since 10.2
35   */
36  class DSSTGradientConverter extends AbstractGradientConverter {
37  
38      /** Fixed dimension of the state. */
39      private static final int FREE_STATE_PARAMETERS = 6;
40  
41      /** Simple constructor.
42       * @param state regular state
43       * @param provider provider to use if attitude needs to be recomputed
44       */
45      DSSTGradientConverter(final SpacecraftState state, final AttitudeProvider provider) {
46  
47          super(FREE_STATE_PARAMETERS);
48  
49          // equinoctial parameters always has derivatives
50          final Gradient sma  = Gradient.variable(FREE_STATE_PARAMETERS, 0, state.getA());
51          final Gradient ex   = Gradient.variable(FREE_STATE_PARAMETERS, 1, state.getEquinoctialEx());
52          final Gradient ey   = Gradient.variable(FREE_STATE_PARAMETERS, 2, state.getEquinoctialEy());
53          final Gradient hx   = Gradient.variable(FREE_STATE_PARAMETERS, 3, state.getHx());
54          final Gradient hy   = Gradient.variable(FREE_STATE_PARAMETERS, 4, state.getHy());
55          final Gradient l    = Gradient.variable(FREE_STATE_PARAMETERS, 5, state.getLM());
56  
57          final Gradient gMu = Gradient.constant(FREE_STATE_PARAMETERS, state.getMu());
58  
59          // date
60          final AbsoluteDate date = state.getDate();
61          final FieldAbsoluteDate<Gradient> dateField = new FieldAbsoluteDate<>(sma.getField(), date);
62  
63          // mass never has derivatives
64          final Gradient gM = Gradient.constant(FREE_STATE_PARAMETERS, state.getMass());
65  
66          final FieldOrbit<Gradient> gOrbit =
67                          new FieldEquinoctialOrbit<>(sma, ex, ey, hx, hy, l,
68                                                      PositionAngleType.MEAN,
69                                                      state.getFrame(),
70                                                      dateField,
71                                                      gMu);
72  
73          final FieldAttitude<Gradient> gAttitude;
74          // compute attitude partial derivatives
75          gAttitude = provider.getAttitude(gOrbit, gOrbit.getDate(), gOrbit.getFrame());
76  
77          // initialize the list with the state having 0 force model parameters
78          initStates(new FieldSpacecraftState<>(gOrbit, gAttitude, gM));
79  
80      }
81  
82  }