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