1   /* Copyright 2002-2026 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
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
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16   */
17  package org.orekit.propagation.analytical.tle;
18  
19  import java.util.List;
20  
21  import org.hipparchus.analysis.differentiation.Gradient;
22  import org.orekit.attitudes.AttitudeProvider;
23  import org.orekit.frames.Frame;
24  import org.orekit.propagation.FieldSpacecraftState;
25  import org.orekit.propagation.analytical.AbstractAnalyticalGradientConverter;
26  import org.orekit.propagation.analytical.tle.generation.TleGenerationAlgorithm;
27  import org.orekit.time.TimeScale;
28  import org.orekit.utils.ParameterDriver;
29  
30  /** Converter for TLE propagator.
31   * @author Luc Maisonobe
32   * @author Bryan Cazabonne
33   * @author Thomas Paulet
34   * @since 11.0
35   */
36  class TLEGradientConverter extends AbstractAnalyticalGradientConverter {
37  
38      /** Fixed dimension of the state. */
39      public static final int FREE_STATE_PARAMETERS = 6;
40  
41      /** Current TLE. */
42      private final TLE tle;
43  
44      /** UTC time scale. */
45      private final TimeScale utc;
46  
47      /** TEME frame. */
48      private final Frame teme;
49  
50      /** Attitude provider. */
51      private final AttitudeProvider provider;
52  
53      /** Propagator. */
54      private final TLEPropagator propagator;
55  
56      /** Simple constructor.
57       * @param propagator TLE propagator used to access initial orbit
58       */
59      TLEGradientConverter(final TLEPropagator propagator) {
60          super(propagator, FREE_STATE_PARAMETERS);
61          // TLE and related parameters
62          this.tle      = propagator.getTLE();
63          this.teme     = propagator.getFrame();
64          this.utc      = tle.getUtc();
65          this.provider = propagator.getAttitudeProvider();
66  
67          this.propagator = propagator;
68  
69      }
70  
71      /** {@inheritDoc} */
72      @Override
73      public FieldTLEPropagator<Gradient> getPropagator() {
74  
75          final FieldSpacecraftState<Gradient> state = getState(this);
76  
77          // Zero
78          final Gradient zero = state.getMass().getField().getZero();
79          final Gradient[] parameters = getParameters(state, propagator);
80  
81          // Template TLE
82          final int satelliteNumber         = tle.getSatelliteNumber();
83          final char classification         = tle.getClassification();
84          final int launchYear              = tle.getLaunchYear();
85          final int launchNumber            = tle.getLaunchNumber();
86          final String launchPiece          = tle.getLaunchPiece();
87          final int ephemerisType           = tle.getEphemerisType();
88          final int elementNumber           = tle.getElementNumber();
89          final int revolutionNumberAtEpoch = tle.getRevolutionNumberAtEpoch();
90  
91          // Initialize the new TLE
92          final FieldTLE<Gradient> templateTLE = new FieldTLE<>(satelliteNumber, classification,
93                                                                launchYear, launchNumber, launchPiece,
94                                                                ephemerisType, elementNumber, state.getDate(),
95                                                                zero, zero, zero, zero, zero, zero, zero, zero,
96                                                                revolutionNumberAtEpoch,
97                                                                parameters[0],
98                                                                utc);
99  
100         // TLE
101         final TleGenerationAlgorithm algorithm = propagator.getTleGenerationAlgorithm();
102         final FieldTLE<Gradient> gTLE = algorithm.generate(state, templateTLE);
103 
104         // Return the "Field" propagator
105         final FieldTLEPropagator<Gradient> fieldPropagator =
106             FieldTLEPropagator.selectExtrapolator(gTLE, provider, state.getMass(), teme);
107         fieldPropagator.setTleGenerationAlgorithm(algorithm);
108         return fieldPropagator;
109     }
110 
111     /** {@inheritDoc} */
112     @Override
113     public List<ParameterDriver> getParametersDrivers() {
114         return  propagator.getParametersDrivers();
115     }
116 
117 }