1 /* Copyright 2002-2022 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
22 /** Generator for one column of a Jacobian matrix.
23 * <p>
24 * This generator is based on variational equations, so
25 * it implements {@link AdditionalDerivativesProvider} and
26 * computes only the derivative of the Jacobian column, to
27 * be integrated by the propagator alongside the primary state.
28 * </p>
29 * @author Luc Maisonobe
30 * @since 11.1
31 */
32 class IntegrableJacobianColumnGenerator
33 implements AdditionalDerivativesProvider, StateTransitionMatrixGenerator.PartialsObserver {
34
35 /** Name of the state for State Transition Matrix. */
36 private final String stmName;
37
38 /** Name of the parameter corresponding to the column. */
39 private final String columnName;
40
41 /** Last value computed for the partial derivatives. */
42 private final double[] pDot;
43
44 /** Simple constructor.
45 * <p>
46 * The generator for State Transition Matrix <em>must</em> be registered as
47 * an integrable generator to the same propagator as the instance, as it
48 * must be scheduled to update the state before the instance
49 * </p>
50 * @param stmGenerator generator for State Transition Matrix
51 * @param columnName name of the parameter corresponding to the column
52 */
53 IntegrableJacobianColumnGenerator(final StateTransitionMatrixGenerator stmGenerator, final String columnName) {
54 this.stmName = stmGenerator.getName();
55 this.columnName = columnName;
56 this.pDot = new double[getDimension()];
57 stmGenerator.addObserver(columnName, this);
58 }
59
60 /** {@inheritDoc} */
61 @Override
62 public String getName() {
63 return columnName;
64 }
65
66 /** Get the dimension of the generated column.
67 * @return dimension of the generated column
68 */
69 public int getDimension() {
70 return 6;
71 }
72
73 /** {@inheritDoc}
74 * <p>
75 * The column derivative can be computed only if the State Transition Matrix derivatives
76 * are available, as it implies the STM generator has already been run.
77 * </p>
78 */
79 @Override
80 public boolean yield(final SpacecraftState state) {
81 return !state.hasAdditionalStateDerivative(stmName);
82 }
83
84 /** {@inheritDoc} */
85 @Override
86 public void partialsComputed(final SpacecraftState state, final double[] factor, final double[] accelerationPartials) {
87 // retrieve current Jacobian column
88 final double[] p = state.getAdditionalState(getName());
89
90 // compute time derivative of the Jacobian column
91 StateTransitionMatrixGenerator.multiplyMatrix(factor, p, pDot, 1);
92 pDot[3] += accelerationPartials[0];
93 pDot[4] += accelerationPartials[1];
94 pDot[5] += accelerationPartials[2];
95 }
96
97 /** {@inheritDoc} */
98 @Override
99 public double[] derivatives(final SpacecraftState s) {
100 return pDot;
101 }
102
103 }
104