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.generation;
18
19 import org.hipparchus.CalculusFieldElement;
20 import org.orekit.annotation.DefaultDataContext;
21 import org.orekit.data.DataContext;
22 import org.orekit.frames.Frame;
23 import org.orekit.orbits.FieldKeplerianOrbit;
24 import org.orekit.orbits.KeplerianOrbit;
25 import org.orekit.orbits.OrbitType;
26 import org.orekit.propagation.FieldSpacecraftState;
27 import org.orekit.propagation.SpacecraftState;
28 import org.orekit.propagation.analytical.tle.FieldTLE;
29 import org.orekit.propagation.analytical.tle.TLE;
30 import org.orekit.propagation.conversion.osc2mean.FixedPointConverter;
31 import org.orekit.propagation.conversion.osc2mean.TLETheory;
32 import org.orekit.time.TimeScale;
33 import org.orekit.utils.ParameterDriver;
34
35 /**
36 * Fixed Point method to reverse SGP4 and SDP4 propagation algorithm
37 * and generate a usable TLE from a spacecraft state.
38 * <p>
39 * Using this algorithm, the B* value is not computed. In other words,
40 * the B* value from the template TLE is set to the generated one.
41 * </p>
42 * @author Thomas Paulet
43 * @author Bryan Cazabonne
44 * @since 12.0
45 */
46 public class FixedPointTleGenerationAlgorithm implements TleGenerationAlgorithm {
47
48 /** Default value for epsilon. */
49 public static final double EPSILON_DEFAULT = 1.0e-10;
50
51 /** Default value for maxIterations. */
52 public static final int MAX_ITERATIONS_DEFAULT = 100;
53
54 /** Default value for scale. */
55 public static final double SCALE_DEFAULT = 1.0;
56
57 /** Osculating to mean orbit converter. */
58 private final FixedPointConverter converter;
59
60 /** UTC time scale. */
61 private final TimeScale utc;
62
63 /**
64 * Default constructor.
65 * <p>
66 * Uses the {@link DataContext#getDefault() default data context}
67 * as well as {@link #EPSILON_DEFAULT}, {@link #MAX_ITERATIONS_DEFAULT},
68 * {@link #SCALE_DEFAULT} for method convergence.
69 * </p>
70 */
71 @DefaultDataContext
72 public FixedPointTleGenerationAlgorithm() {
73 this(EPSILON_DEFAULT, MAX_ITERATIONS_DEFAULT, SCALE_DEFAULT);
74 }
75
76 /**
77 * Constructor.
78 * <p>
79 * Uses the {@link DataContext#getDefault() default data context}.
80 * </p>
81 * @param epsilon used to compute threshold for convergence check
82 * @param maxIterations maximum number of iterations for convergence
83 * @param scale scale factor of the Fixed Point algorithm
84 */
85 @DefaultDataContext
86 public FixedPointTleGenerationAlgorithm(final double epsilon,
87 final int maxIterations,
88 final double scale) {
89 this(epsilon, maxIterations, scale,
90 DataContext.getDefault().getTimeScales().getUTC(),
91 DataContext.getDefault().getFrames().getTEME());
92 }
93
94 /**
95 * Constructor.
96 * @param epsilon used to compute threshold for convergence check
97 * @param maxIterations maximum number of iterations for convergence
98 * @param scale scale factor of the Fixed Point algorithm
99 * @param utc UTC time scale
100 * @param teme TEME frame
101 */
102 public FixedPointTleGenerationAlgorithm(final double epsilon,
103 final int maxIterations,
104 final double scale,
105 final TimeScale utc,
106 final Frame teme) {
107 this.converter = new FixedPointConverter(new TLETheory(utc, teme),
108 epsilon,
109 maxIterations,
110 scale);
111 this.utc = utc;
112 }
113
114 /** {@inheritDoc} */
115 @Override
116 public TLE generate(final SpacecraftState state, final TLE templateTLE) {
117 final KeplerianOrbit mean = (KeplerianOrbit) OrbitType.KEPLERIAN.convertType(converter.convertToMean(state.getOrbit()));
118 final TLE tle = TleGenerationUtil.newTLE(mean, templateTLE, templateTLE.getBStar(mean.getDate()), utc);
119 // reset estimated parameters from template to generated tle
120 for (final ParameterDriver templateDrivers : templateTLE.getParametersDrivers()) {
121 if (templateDrivers.isSelected()) {
122 // set to selected for the new TLE
123 tle.getParameterDriver(templateDrivers.getName()).setSelected(true);
124 }
125 }
126 return tle;
127 }
128
129 /** {@inheritDoc} */
130 @Override
131 public <T extends CalculusFieldElement<T>> FieldTLE<T> generate(final FieldSpacecraftState<T> state,
132 final FieldTLE<T> templateTLE) {
133 final T bStar = state.getMass().getField().getZero().newInstance(templateTLE.getBStar());
134 final FieldKeplerianOrbit<T> mean = (FieldKeplerianOrbit<T>) OrbitType.KEPLERIAN.convertType(converter.convertToMean(state.getOrbit()));
135 final FieldTLE<T> tle = TleGenerationUtil.newTLE(mean, templateTLE, bStar, utc);
136 // reset estimated parameters from template to generated tle
137 for (final ParameterDriver templateDrivers : templateTLE.getParametersDrivers()) {
138 if (templateDrivers.isSelected()) {
139 // set to selected for the new TLE
140 tle.getParameterDriver(templateDrivers.getName()).setSelected(true);
141 }
142 }
143 return tle;
144 }
145
146 }