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  /** Observer for {@link KalmanEstimator Kalman filter} estimations.
20   * <p>
21   * This interface is intended to be implemented by users to monitor
22   * the progress of the Kalman filter estimator during estimation.
23   * </p>
24   * @author Luc Maisonobe
25   * @author Maxime Journot
26   * @since 9.2
27   */
28  @FunctionalInterface
29  public interface KalmanObserver {
30  
31      /** Initialise the observer on the initial state of the filter, before processing the first measurement.
32       * @param estimation estimation performed by Kalman estimator
33       */
34      default void init(KalmanEstimation estimation) {
35      }
36  
37      /** Notification callback after each one of a Kalman filter estimation.
38       * @param estimation estimation performed by Kalman estimator
39       */
40      void evaluationPerformed(KalmanEstimation estimation);
41  
42  }