1   /* Copyright 2002-2021 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.forces.empirical;
18  
19  import java.util.List;
20  
21  import org.hipparchus.CalculusFieldElement;
22  import org.orekit.propagation.FieldSpacecraftState;
23  import org.orekit.propagation.SpacecraftState;
24  import org.orekit.time.AbsoluteDate;
25  import org.orekit.utils.ParameterDriver;
26  
27  /** Acceleration model used by empirical force.
28   * @author Bryan Cazabonne
29   * @since 10.3
30   */
31  public interface AccelerationModel {
32  
33      /** Initialize the acceleration model at the start of the propagation.
34       * <p>
35       * The default implementation of this method does nothing
36       * </p>
37       * @param initialState spacecraft state at the start of propagation.
38       * @param target       date of propagation. Not equal to {@code initialState.getDate()}.
39       */
40      default void init(SpacecraftState initialState, AbsoluteDate target) {
41          // Nothing by default
42      }
43  
44      /** Compute the signed amplitude of the acceleration.
45       * <p>
46       * The acceleration is the direction multiplied by the signed amplitude. So if
47       * signed amplitude is negative, the acceleratin is towards the opposite of the
48       * direction specified at construction.
49       * </p>
50       * @param state current state information: date, kinematics, attitude
51       * @param parameters values of the force model parameters
52       * @return norm of the acceleration
53       */
54      double signedAmplitude(SpacecraftState state, double[] parameters);
55  
56      /** Compute the signed amplitude of the acceleration.
57       * <p>
58       * The acceleration is the direction multiplied by the signed amplitude. So if
59       * signed amplitude is negative, the acceleratin is towards the opposite of the
60       * direction specified at construction.
61       * </p>
62       * @param state current state information: date, kinematics, attitude
63       * @param parameters values of the force model parameters
64       * @param <T> type of the elements
65       * @return norm of the acceleration
66       */
67      <T extends CalculusFieldElement<T>> T signedAmplitude(FieldSpacecraftState<T> state, T[] parameters);
68  
69      /** Get the drivers for acceleration model parameters.
70       * @return drivers for acceleration model parameters
71       */
72      List<ParameterDriver> getParametersDrivers();
73  
74  }