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.gnss.OneWayGNSSRangeRate;
21  import org.orekit.propagation.SpacecraftState;
22  import org.orekit.utils.PVCoordinates;
23  
24  /** Class modifying theoretical range-rate measurement with relativistic frequency deviation.
25   * It works only with orbit-based states.
26   * <p>
27   * Relativistic clock correction is caused by the motion of the satellite as well as
28   * the change in the gravitational potential
29   * </p>
30   * @author Luc Maisonobe
31   * @since 12.1
32   *
33   * @see "Teunissen, Peter, and Oliver Montenbruck, eds. Springer handbook of global navigation
34   * satellite systems. Chapter 19.2. Springer, 2017."
35   */
36  public class RelativisticClockOneWayGNSSRangeRateModifier
37      extends AbstractRelativisticClockOnBoardRangeRateModifier<OneWayGNSSRangeRate> {
38  
39      /** Simple constructor.
40       * @param gm gravitational constant for main body in signal path vicinity.
41       */
42      public RelativisticClockOneWayGNSSRangeRateModifier(final double gm) {
43          super(gm);
44      }
45  
46      /** {@inheritDoc} */
47      @Override
48      public void modifyWithoutDerivatives(final EstimatedMeasurementBase<OneWayGNSSRangeRate> estimated) {
49  
50          // local satellite
51          final SpacecraftState local = estimated.getStates()[0];
52  
53          // compute semi major axis of remote (transmitter) satellite
54          final PVCoordinates remote  = estimated.getParticipants()[0];
55          final double        rRemote = remote.getPosition().getNorm();
56          final double        vRemote = remote.getVelocity().getNorm();
57          final double        aRemote = 1.0 / (2 / rRemote - vRemote * vRemote / getGm());
58  
59          modifyWithoutDerivatives(estimated,
60                                   local.getOrbit().getA(), local.getPosition().getNorm(),
61                                   aRemote, rRemote);
62  
63      }
64  
65  }