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.estimation.sequential;
18  
19  import org.hipparchus.linear.RealMatrix;
20  import org.orekit.propagation.SpacecraftState;
21  
22  /** Provider for constant process noise matrices.
23   * <p>
24   * This class always provides one initial noise matrix and
25   * one constant process noise matrix (both can be identical),
26   * regardless of states.
27   * </p>
28   * @author Luc Maisonobe
29   * @since 9.2
30   */
31  public class ConstantProcessNoise extends AbstractCovarianceMatrixProvider {
32  
33      /** Constant process noise. */
34      private final RealMatrix processNoiseMatrix;
35  
36      /** Simple constructor.
37       * @param processNoiseMatrix constant process noise, used for both initial noise
38       * and noise between previous and current state
39       */
40      public ConstantProcessNoise(final RealMatrix processNoiseMatrix) {
41          this(processNoiseMatrix, processNoiseMatrix);
42      }
43  
44      /** Simple constructor.
45       * @param initialNoiseMatrix initial process noise
46       * @param processNoiseMatrix constant process noise
47       */
48      public ConstantProcessNoise(final RealMatrix initialNoiseMatrix, final RealMatrix processNoiseMatrix) {
49          super(initialNoiseMatrix);
50          this.processNoiseMatrix = processNoiseMatrix;
51      }
52  
53      /** {@inheritDoc} */
54      @Override
55      public RealMatrix getProcessNoiseMatrix(final SpacecraftState previous,
56                                              final SpacecraftState current) {
57          return processNoiseMatrix;
58      }
59  
60  }