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3    * contributor license agreements.  See the NOTICE file distributed with
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5    * CS licenses this file to You under the Apache License, Version 2.0
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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,
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14   * See the License for the specific language governing permissions and
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17  package org.orekit.estimation.measurements.modifiers;
18  
19  import java.util.List;
20  
21  import org.hipparchus.CalculusFieldElement;
22  import org.orekit.estimation.measurements.GroundStation;
23  import org.orekit.frames.TopocentricFrame;
24  import org.orekit.models.earth.ionosphere.IonosphericModel;
25  import org.orekit.propagation.FieldSpacecraftState;
26  import org.orekit.propagation.SpacecraftState;
27  import org.orekit.utils.ParameterDriver;
28  
29  /** Base class modifying theoretical range-rate measurement with ionospheric delay.
30   * The effect of ionospheric correction on the range-rate is directly computed
31   * through the computation of the ionospheric delay difference with respect to
32   * time.
33   *
34   * The ionospheric delay depends on the frequency of the signal (GNSS, VLBI, ...).
35   * For optical measurements (e.g. SLR), the ray is not affected by ionosphere charged particles.
36   * <p>
37   * Since 10.0, state derivatives and ionospheric parameters derivates are computed
38   * using automatic differentiation.
39   * </p>
40   * @author Joris Olympio
41   * @since 11.2
42   */
43  public abstract class BaseRangeRateIonosphericDelayModifier {
44  
45      /** Ionospheric delay model. */
46      private final IonosphericModel ionoModel;
47  
48      /** Frequency [Hz]. */
49      private final double frequency;
50  
51      /** Constructor.
52       *
53       * @param model Ionospheric delay model appropriate for the current range-rate measurement method.
54       * @param freq frequency of the signal in Hz
55       */
56      protected BaseRangeRateIonosphericDelayModifier(final IonosphericModel model, final double freq) {
57          this.ionoModel = model;
58          this.frequency = freq;
59      }
60  
61      /** Get the name of the effect modifying the measurement.
62       * @return name of the effect modifying the measurement
63       * @since 13.0
64       */
65      public String getEffectName() {
66          return "ionosphere";
67      }
68  
69      /** Get the ionospheric delay model.
70       * @return ionospheric delay model
71       */
72      protected IonosphericModel getIonoModel() {
73          return ionoModel;
74      }
75  
76      /** Compute the measurement error due to Ionosphere.
77       * @param station station
78       * @param state spacecraft state
79       * @return the measurement error due to Ionosphere
80       */
81      protected double rangeRateErrorIonosphericModel(final GroundStation station, final SpacecraftState state) {
82          final double dt = 10; // s
83          // Base frame associated with the station
84          final TopocentricFrame baseFrame = station.getBaseFrame();
85          // delay in meters
86          final double delay1 = ionoModel.pathDelay(state, baseFrame, frequency, ionoModel.getParameters(state.getDate()));
87          // propagate spacecraft state forward by dt
88          final SpacecraftState state2 = state.shiftedBy(dt);
89          // ionospheric delay dt after in meters
90          final double delay2 = ionoModel.pathDelay(state2, baseFrame, frequency, ionoModel.getParameters(state.getDate()));
91          // delay in meters
92          return (delay2 - delay1) / dt;
93      }
94  
95      /** Compute the measurement error due to Ionosphere.
96       * @param <T> type of the elements
97       * @param station station
98       * @param state spacecraft state
99       * @param parameters ionospheric model parameters
100      * @return the measurement error due to Ionosphere
101      */
102     protected <T extends CalculusFieldElement<T>> T rangeRateErrorIonosphericModel(final GroundStation station,
103                                                                                    final FieldSpacecraftState<T> state,
104                                                                                    final T[] parameters) {
105         final double dt = 10; // s
106         // Base frame associated with the station
107         final TopocentricFrame baseFrame = station.getBaseFrame();
108         // delay in meters
109         final T delay1 = ionoModel.pathDelay(state, baseFrame, frequency, parameters);
110         // propagate spacecraft state forward by dt
111         final FieldSpacecraftState<T> state2 = state.shiftedBy(dt);
112         // ionospheric delay dt after in meters
113         final T delay2 = ionoModel.pathDelay(state2, baseFrame, frequency, parameters);
114         // delay in meters
115         return delay2.subtract(delay1).divide(dt);
116     }
117 
118     /** Get the drivers for this modifier parameters.
119      * @return drivers for this modifier parameters
120      */
121     public List<ParameterDriver> getParametersDrivers() {
122         return ionoModel.getParametersDrivers();
123     }
124 
125 }