1   /* Copyright 2022-2025 Thales Alenia Space
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.measurements.modifiers;
18  
19  import org.orekit.estimation.measurements.EstimatedMeasurementBase;
20  import org.orekit.estimation.measurements.EstimationModifier;
21  import org.orekit.estimation.measurements.ObservedMeasurement;
22  import org.orekit.utils.Constants;
23  import org.orekit.utils.ParameterDriver;
24  
25  import java.util.Collections;
26  import java.util.List;
27  
28  /** Class modifying theoretical range-rate measurement with relativistic frequency deviation.
29   * <p>
30   * Relativistic clock correction is caused by the motion of the satellite as well as
31   * the change in the gravitational potential
32   * </p>
33   * @param <T> type of the measurement
34   * @author Luc Maisonobe
35   * @since 12.1
36   *
37   * @see "Teunissen, Peter, and Oliver Montenbruck, eds. Springer handbook of global navigation
38   * satellite systems. Chapter 19.2. Springer, 2017."
39   */
40  public abstract class AbstractRelativisticClockOnBoardRangeRateModifier<T extends ObservedMeasurement<T>>
41      extends AbstractRelativisticClockModifier implements EstimationModifier<T> {
42  
43      /** Gravitational constant. */
44      private final double gm;
45  
46      /** Simple constructor.
47       * @param gm gravitational constant for main body in signal path vicinity.
48       */
49      public AbstractRelativisticClockOnBoardRangeRateModifier(final double gm) {
50          super();
51          this.gm = gm;
52      }
53  
54      /** {@inheritDoc} */
55      @Override
56      public String getEffectName() {
57          return "clock relativity";
58      }
59  
60      /** Get gravitational constant for main body in signal path vicinity.
61       * @return gravitational constant for main body in signal path vicinity
62       */
63      protected double getGm() {
64          return gm;
65      }
66  
67      /** {@inheritDoc} */
68      @Override
69      public List<ParameterDriver> getParametersDrivers() {
70          return Collections.emptyList();
71      }
72  
73      /** Apply relativistic frequency deviation.
74       * @param estimated estimated measurement to modify
75       * @param aLocal semi major axis or local (receiver) satellite
76       * @param rLocal distance of local (receiver) satellite to central body center
77       * @param aRemote semi major axis or remote (transmitter) satellite
78       * @param rRemote distance of remote (transmitter) satellite to central body center
79       */
80      protected void modifyWithoutDerivatives(final EstimatedMeasurementBase<T> estimated,
81                                              final double aLocal,  final double rLocal,
82                                              final double aRemote, final double rRemote) {
83  
84          // compute relativistic frequency deviation
85          final double factor   = -gm * getScaleFactor();
86          final double dfLocal  = factor * (1.0 / aLocal  - 1.0 / rLocal);
87          final double dfRemote = factor * (1.0 / aRemote - 1.0 / rRemote);
88  
89          // Update estimated value taking into account the relativistic effect.
90          final double[] newValue = estimated.getEstimatedValue().clone();
91          newValue[0] = newValue[0] + (dfLocal - dfRemote) * Constants.SPEED_OF_LIGHT;
92          estimated.modifyEstimatedValue(this, newValue);
93  
94      }
95  
96  }