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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
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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
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16   */
17  
18  package org.orekit.estimation.measurements.modifiers;
19  
20  import java.util.Collections;
21  import java.util.List;
22  
23  import org.orekit.estimation.measurements.EstimatedMeasurementBase;
24  import org.orekit.estimation.measurements.EstimationModifier;
25  import org.orekit.estimation.measurements.Range;
26  import org.orekit.utils.Constants;
27  import org.orekit.utils.ParameterDriver;
28  
29  /**
30   * Class modifying theoretical range measurements with relativistic J2 clock correction.
31   * <p>
32   * Relativistic clock correction of the effects caused by the oblateness of Earth on
33   * the gravity potential.
34   * </p>
35   * <p>
36   * The time delay caused by this effect is computed based on the orbital parameters of the
37   * emitter's orbit.
38   * </p>
39   *
40   * @author Louis Aucouturier
41   * @since 11.2
42   *
43   * @see "Teunissen, Peter, and Oliver Montenbruck, eds. Springer handbook of global navigation
44   * satellite systems. Chapter 19.2. Equation 19.18 Springer, 2017."
45   */
46  
47  public class RelativisticJ2ClockRangeModifier extends AbstractRelativisticJ2ClockModifier implements EstimationModifier<Range> {
48  
49      /**
50       * Modifier constructor.
51       * @param gm Earth gravitational constant (mu) in m³/s².
52       * @param c20 Earth un-normalized second zonal coefficient (Signed J2 constant, is negative) (Typical value -1.0826e-3).
53       * @param equatorialRadius Earth equatorial radius in m.
54       */
55      public RelativisticJ2ClockRangeModifier(final double gm,
56                                              final double c20,
57                                              final double equatorialRadius) {
58          super(gm, c20, equatorialRadius);
59      }
60  
61      /** {@inheritDoc} */
62      public List<ParameterDriver> getParametersDrivers() {
63          return Collections.emptyList();
64      }
65  
66      /** {@inheritDoc} */
67      @Override
68      public void modifyWithoutDerivatives(final EstimatedMeasurementBase<Range> estimated) {
69          // Relativistic effect
70          final double dtJ2 = relativisticJ2Correction(estimated);
71  
72          // Update estimated value taking into account the relativistic effect.
73          final double[] newValue = estimated.getEstimatedValue().clone();
74          newValue[0] = newValue[0] - dtJ2 * Constants.SPEED_OF_LIGHT;
75          estimated.modifyEstimatedValue(this, newValue);
76      }
77  
78  }