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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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9    *   http://www.apache.org/licenses/LICENSE-2.0
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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.Arrays;
20  
21  import org.hipparchus.analysis.differentiation.Gradient;
22  import org.orekit.estimation.measurements.EstimatedMeasurement;
23  import org.orekit.estimation.measurements.EstimatedMeasurementBase;
24  import org.orekit.estimation.measurements.EstimationModifier;
25  import org.orekit.estimation.measurements.GroundStation;
26  import org.orekit.estimation.measurements.ObservedMeasurement;
27  import org.orekit.propagation.FieldSpacecraftState;
28  import org.orekit.propagation.SpacecraftState;
29  import org.orekit.propagation.integration.AbstractGradientConverter;
30  import org.orekit.utils.Differentiation;
31  import org.orekit.utils.ParameterDriver;
32  import org.orekit.utils.ParameterDriversProvider;
33  import org.orekit.utils.TimeSpanMap.Span;
34  
35  /** Utility class for TDOA measurements.
36   * @author Pascal Parraud
37   * @since 11.2
38   */
39  class TDOAModifierUtil {
40  
41      /** Private constructor for utility class.*/
42      private TDOAModifierUtil() {
43          // not used
44      }
45  
46      /** Apply a modifier to an estimated measurement.
47       * @param <T> type of the measurement
48       * @param estimated estimated measurement to modify
49       * @param primeStation prime station
50       * @param secondStation second station
51       * @param modelEffect model effect
52       * @param modifier applied modifier
53       * @since 12.1
54       */
55      public static <T extends ObservedMeasurement<T>> void modifyWithoutDerivatives(final EstimatedMeasurementBase<T> estimated,
56                                                                                     final GroundStation primeStation,
57                                                                                     final GroundStation secondStation,
58                                                                                     final ParametricModelEffect modelEffect,
59                                                                                     final EstimationModifier<T> modifier) {
60  
61          final SpacecraftState state       = estimated.getStates()[0];
62          final double[]        oldValue    = estimated.getEstimatedValue();
63          final double          primeDelay  = modelEffect.evaluate(primeStation, state);
64          final double          secondDelay = modelEffect.evaluate(secondStation, state);
65  
66          // Update estimated value taking into account the delay for each downlink. The time delay is directly applied to the TDOA.
67          final double[] newValue = oldValue.clone();
68          newValue[0] += primeDelay;
69          newValue[0] -= secondDelay;
70          estimated.modifyEstimatedValue(modifier, newValue);
71      }
72  
73      /** Apply a modifier to an estimated measurement.
74       * @param <T> type of the measurement
75       * @param estimated estimated measurement to modify
76       * @param primeStation prime station
77       * @param secondStation second station
78       * @param converter gradient converter
79       * @param parametricModel parametric modifier model
80       * @param modelEffect model effect
81       * @param modelEffectGradient model effect gradient
82       * @param modifier applied modifier
83       * @since 12.1
84       */
85      public static <T extends ObservedMeasurement<T>> void modify(final EstimatedMeasurement<T> estimated,
86                                                                   final ParameterDriversProvider parametricModel,
87                                                                   final AbstractGradientConverter converter,
88                                                                   final GroundStation primeStation, final GroundStation secondStation,
89                                                                   final ParametricModelEffect modelEffect,
90                                                                   final ParametricModelEffectGradient modelEffectGradient,
91                                                                   final EstimationModifier<T> modifier) {
92  
93          final SpacecraftState state    = estimated.getStates()[0];
94          final double[]        oldValue = estimated.getEstimatedValue();
95  
96          // Update estimated derivatives with Jacobian of the measure wrt state
97          final FieldSpacecraftState<Gradient> gState = converter.getState(parametricModel);
98          final Gradient[] gParameters       = converter.getParameters(gState, parametricModel);
99          final Gradient   primeGDelay       = modelEffectGradient.evaluate(primeStation, gState, gParameters);
100         final Gradient   secondGDelay      = modelEffectGradient.evaluate(secondStation, gState, gParameters);
101         final double[]   primeDerivatives  = primeGDelay.getGradient();
102         final double[]   secondDerivatives = secondGDelay.getGradient();
103 
104         final double[][] stateDerivatives  = estimated.getStateDerivatives(0);
105         for (int jcol = 0; jcol < stateDerivatives[0].length; ++jcol) {
106             stateDerivatives[0][jcol] += primeDerivatives[jcol];
107             stateDerivatives[0][jcol] -= secondDerivatives[jcol];
108         }
109         estimated.setStateDerivatives(0, stateDerivatives);
110 
111         int index = 0;
112         for (final ParameterDriver driver : parametricModel.getParametersDrivers()) {
113             if (driver.isSelected()) {
114                 for (Span<String> span = driver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {
115 
116                     // update estimated derivatives with derivative of the modification wrt modifier parameters
117                     double parameterDerivative = estimated.getParameterDerivatives(driver, span.getStart())[0];
118                     parameterDerivative += primeDerivatives[index + converter.getFreeStateParameters()];
119                     parameterDerivative -= secondDerivatives[index + converter.getFreeStateParameters()];
120                     estimated.setParameterDerivatives(driver, span.getStart(), parameterDerivative);
121                     index += 1;
122                 }
123             }
124 
125         }
126 
127         // Update derivatives with respect to primary station position
128         for (final ParameterDriver driver : Arrays.asList(primeStation.getClockOffsetDriver(),
129                                                           primeStation.getEastOffsetDriver(),
130                                                           primeStation.getNorthOffsetDriver(),
131                                                           primeStation.getZenithOffsetDriver())) {
132             if (driver.isSelected()) {
133                 for (Span<String> span = driver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {
134 
135                     double parameterDerivative = estimated.getParameterDerivatives(driver, span.getStart())[0];
136                     parameterDerivative += Differentiation.differentiate((d, t) -> modelEffect.evaluate(primeStation, state),
137                                                                      3, 10.0 * driver.getScale()).value(driver, state.getDate());
138                     estimated.setParameterDerivatives(driver, span.getStart(), parameterDerivative);
139                 }
140             }
141         }
142 
143         // Update derivatives with respect to secondary station position
144         for (final ParameterDriver driver : Arrays.asList(secondStation.getClockOffsetDriver(),
145                                                           secondStation.getEastOffsetDriver(),
146                                                           secondStation.getNorthOffsetDriver(),
147                                                           secondStation.getZenithOffsetDriver())) {
148             if (driver.isSelected()) {
149                 for (Span<String> span = driver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {
150 
151                     double parameterDerivative = estimated.getParameterDerivatives(driver, span.getStart())[0];
152                     parameterDerivative -= Differentiation.differentiate((d, t) -> modelEffect.evaluate(secondStation, state),
153                                                                      3, 10.0 * driver.getScale()).value(driver, state.getDate());
154                     estimated.setParameterDerivatives(driver, span.getStart(), parameterDerivative);
155                 }
156             }
157         }
158 
159         // Update estimated value taking into account the delay for each downlink.  The time delay is directly applied to the TDOA.
160         final double[] newValue = oldValue.clone();
161         newValue[0] += primeGDelay.getReal();
162         newValue[0] -= secondGDelay.getReal();
163         estimated.modifyEstimatedValue(modifier, newValue);
164     }
165 
166 }