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.numerical;
18
19 import org.orekit.propagation.SpacecraftState;
20 import org.orekit.propagation.integration.AdditionalDerivativesProvider;
21 import org.orekit.propagation.integration.CombinedDerivatives;
22
23 /** Generator for one column of a Jacobian matrix.
24 * <p>
25 * This generator is based on variational equations, so
26 * it implements {@link AdditionalDerivativesProvider} and
27 * computes only the derivative of the Jacobian column, to
28 * be integrated by the propagator alongside the primary state.
29 * </p>
30 * @author Luc Maisonobe
31 * @since 11.1
32 */
33 class IntegrableJacobianColumnGenerator
34 implements AdditionalDerivativesProvider, StateTransitionMatrixGenerator.PartialsObserver {
35
36 /** Name of the state for State Transition Matrix. */
37 private final String stmName;
38
39 /** Name of the parameter corresponding to the column. */
40 private final String columnName;
41
42 /** Last value computed for the partial derivatives. */
43 private final double[] pDot;
44
45 /** Simple constructor.
46 * <p>
47 * The generator for State Transition Matrix <em>must</em> be registered as
48 * an integrable generator to the same propagator as the instance, as it
49 * must be scheduled to update the state before the instance
50 * </p>
51 * @param stmGenerator generator for State Transition Matrix
52 * @param columnName name of the parameter corresponding to the column
53 */
54 IntegrableJacobianColumnGenerator(final StateTransitionMatrixGenerator stmGenerator, final String columnName) {
55 this.stmName = stmGenerator.getName();
56 this.columnName = columnName;
57 this.pDot = new double[getDimension()];
58 stmGenerator.addObserver(columnName, this);
59 }
60
61 /** {@inheritDoc} */
62 @Override
63 public String getName() {
64 return columnName;
65 }
66
67 /** Get the dimension of the generated column.
68 * @return dimension of the generated column
69 */
70 public int getDimension() {
71 return 6;
72 }
73
74 /** {@inheritDoc}
75 * <p>
76 * The column derivative can be computed only if the State Transition Matrix derivatives
77 * are available, as it implies the STM generator has already been run.
78 * </p>
79 */
80 @Override
81 public boolean yields(final SpacecraftState state) {
82 return !state.hasAdditionalStateDerivative(stmName);
83 }
84
85 /** {@inheritDoc} */
86 @Override
87 public void partialsComputed(final SpacecraftState state, final double[] factor, final double[] accelerationPartials) {
88 // retrieve current Jacobian column
89 final double[] p = state.getAdditionalState(getName());
90
91 // compute time derivative of the Jacobian column
92 StateTransitionMatrixGenerator.multiplyMatrix(factor, p, pDot, 1);
93 pDot[3] += accelerationPartials[0];
94 pDot[4] += accelerationPartials[1];
95 pDot[5] += accelerationPartials[2];
96 }
97
98 /** {@inheritDoc} */
99 @Override
100 public CombinedDerivatives combinedDerivatives(final SpacecraftState s) {
101 return new CombinedDerivatives(pDot, null);
102 }
103
104 }
105