TurnAroundRangeTroposphericDelayModifier.java

  1. /* Copyright 2002-2024 CS GROUP
  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;

  19. import java.util.Arrays;
  20. import java.util.List;

  22. import org.hipparchus.CalculusFieldElement;
  23. import org.hipparchus.Field;
  24. import org.hipparchus.analysis.differentiation.Gradient;
  25. import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
  26. import org.hipparchus.geometry.euclidean.threed.Vector3D;
  27. import org.orekit.attitudes.FrameAlignedProvider;
  28. import org.orekit.estimation.measurements.EstimatedMeasurement;
  29. import org.orekit.estimation.measurements.EstimatedMeasurementBase;
  30. import org.orekit.estimation.measurements.EstimationModifier;
  31. import org.orekit.estimation.measurements.GroundStation;
  32. import org.orekit.estimation.measurements.TurnAroundRange;
  33. import org.orekit.models.earth.troposphere.DiscreteTroposphericModel;
  34. import org.orekit.propagation.FieldSpacecraftState;
  35. import org.orekit.propagation.SpacecraftState;
  36. import org.orekit.time.AbsoluteDate;
  37. import org.orekit.utils.Differentiation;
  38. import org.orekit.utils.ParameterDriver;
  39. import org.orekit.utils.ParameterFunction;
  40. import org.orekit.utils.TimeSpanMap.Span;

  42. /** Class modifying theoretical turn-around TurnAroundRange measurement with tropospheric delay.
  43.  * The effect of tropospheric correction on the TurnAroundRange is directly computed
  44.  * through the computation of the tropospheric delay.
  45.  *
  46.  * In general, for GNSS, VLBI, ... there is hardly any frequency dependence in the delay.
  47.  * For SLR techniques however, the frequency dependence is sensitive.
  48.  *
  49.  * @author Maxime Journot
  50.  * @since 9.0
  51.  */
  52. public class TurnAroundRangeTroposphericDelayModifier implements EstimationModifier<TurnAroundRange> {

  54.     /** Tropospheric delay model. */
  55.     private final DiscreteTroposphericModel tropoModel;

  57.     /** Constructor.
  58.      *
  59.      * @param model  Tropospheric delay model appropriate for the current TurnAroundRange measurement method.
  60.      */
  61.     public TurnAroundRangeTroposphericDelayModifier(final DiscreteTroposphericModel model) {
  62.         tropoModel = model;
  63.     }

  65.     /** Compute the measurement error due to Troposphere.
  66.      * @param station station
  67.      * @param state spacecraft state
  68.      * @return the measurement error due to Troposphere
  69.      */
  70.     private double rangeErrorTroposphericModel(final GroundStation station, final SpacecraftState state) {
  71.         //
  72.         final Vector3D position = state.getPosition();

  74.         // elevation
  75.         final double elevation =
  76.                         station.getBaseFrame().getTrackingCoordinates(position, state.getFrame(), state.getDate()).
  77.                         getElevation();

  79.         // only consider measures above the horizon
  80.         if (elevation > 0) {
  81.             // Delay in meters
  82.             final double delay = tropoModel.pathDelay(elevation, station.getBaseFrame().getPoint(), tropoModel.getParameters(state.getDate()), state.getDate());

  84.             return delay;
  85.         }

  87.         return 0;
  88.     }

  90.     /** Compute the measurement error due to Troposphere.
  91.      * @param <T> type of the element
  92.      * @param station station
  93.      * @param state spacecraft state
  94.      * @param parameters tropospheric model parameters
  95.      * @return the measurement error due to Troposphere
  96.      */
  97.     private <T extends CalculusFieldElement<T>> T rangeErrorTroposphericModel(final GroundStation station,
  98.                                                                           final FieldSpacecraftState<T> state,
  99.                                                                           final T[] parameters) {
  100.         // Field
  101.         final Field<T> field = state.getDate().getField();
  102.         final T zero         = field.getZero();

  104.         //
  105.         final FieldVector3D<T> position = state.getPosition();
  106.         final T dsElevation             =
  107.                         station.getBaseFrame().getTrackingCoordinates(position,  state.getFrame(), state.getDate()).
  108.                         getElevation();

  110.         // only consider measures above the horizon
  111.         if (dsElevation.getReal() > 0) {
  112.             // Delay in meters
  113.             final T delay = tropoModel.pathDelay(dsElevation, station.getBaseFrame().getPoint(field), parameters, state.getDate());

  115.             return delay;
  116.         }

  118.         return zero;
  119.     }

  121.     /** Compute the Jacobian of the delay term wrt state using
  122.     * automatic differentiation.
  123.     *
  124.     * @param derivatives tropospheric delay derivatives
  125.     *
  126.     * @return Jacobian of the delay wrt state
  127.     */
  128.     private double[][] rangeErrorJacobianState(final double[] derivatives) {
  129.         final double[][] finiteDifferencesJacobian = new double[1][6];
  130.         System.arraycopy(derivatives, 0, finiteDifferencesJacobian[0], 0, 6);
  131.         return finiteDifferencesJacobian;
  132.     }


  135.     /** Compute the derivative of the delay term wrt parameters.
  136.      *
  137.      * @param station ground station
  138.      * @param driver driver for the station offset parameter
  139.      * @param state spacecraft state
  140.      * @return derivative of the delay wrt station offset parameter
  141.      */
  142.     private double rangeErrorParameterDerivative(final GroundStation station,
  143.                                                  final ParameterDriver driver,
  144.                                                  final SpacecraftState state) {

  146.         final ParameterFunction rangeError = new ParameterFunction() {
  147.             /** {@inheritDoc} */
  148.             @Override
  149.             public double value(final ParameterDriver parameterDriver, final AbsoluteDate date) {
  150.                 return rangeErrorTroposphericModel(station, state);
  151.             }
  152.         };

  154.         final ParameterFunction rangeErrorDerivative = Differentiation.differentiate(rangeError, 3, 10.0 * driver.getScale());

  156.         return rangeErrorDerivative.value(driver, state.getDate());

  158.     }

  160.     /** Compute the derivative of the delay term wrt parameters using
  161.     * automatic differentiation.
  162.     *
  163.     * @param derivatives tropospheric delay derivatives
  164.     * @param freeStateParameters dimension of the state.
  165.     * @return derivative of the delay wrt tropospheric model parameters
  166.     */
  167.     private double[] rangeErrorParameterDerivative(final double[] derivatives, final int freeStateParameters) {
  168.         // 0 ... freeStateParameters - 1 -> derivatives of the delay wrt state
  169.         // freeStateParameters ... n     -> derivatives of the delay wrt tropospheric parameters
  170.         final int dim = derivatives.length - freeStateParameters;
  171.         final double[] rangeError = new double[dim];

  173.         for (int i = 0; i < dim; i++) {
  174.             rangeError[i] = derivatives[freeStateParameters + i];
  175.         }

  177.         return rangeError;
  178.     }

  180.     /** {@inheritDoc} */
  181.     @Override
  182.     public List<ParameterDriver> getParametersDrivers() {
  183.         return tropoModel.getParametersDrivers();
  184.     }

  186.     /** {@inheritDoc} */
  187.     @Override
  188.     public void modifyWithoutDerivatives(final EstimatedMeasurementBase<TurnAroundRange> estimated) {

  190.         final TurnAroundRange measurement      = estimated.getObservedMeasurement();
  191.         final GroundStation   primaryStation   = measurement.getPrimaryStation();
  192.         final GroundStation   secondaryStation = measurement.getSecondaryStation();
  193.         final SpacecraftState state            = estimated.getStates()[0];

  195.         // Update estimated value taking into account the tropospheric delay.
  196.         // The tropospheric delay is directly added to the TurnAroundRange.
  197.         final double[] newValue       = estimated.getEstimatedValue();
  198.         final double   primaryDelay   = rangeErrorTroposphericModel(primaryStation, state);
  199.         final double   secondaryDelay = rangeErrorTroposphericModel(secondaryStation, state);
  200.         newValue[0] = newValue[0] + primaryDelay + secondaryDelay;
  201.         estimated.setEstimatedValue(newValue);

  203.     }
  204.     /** {@inheritDoc} */
  205.     @Override
  206.     public void modify(final EstimatedMeasurement<TurnAroundRange> estimated) {
  207.         final TurnAroundRange measurement      = estimated.getObservedMeasurement();
  208.         final GroundStation   primaryStation   = measurement.getPrimaryStation();
  209.         final GroundStation   secondaryStation = measurement.getSecondaryStation();
  210.         final SpacecraftState state            = estimated.getStates()[0];

  212.         final double[] oldValue = estimated.getEstimatedValue();

  214.         // Update estimated derivatives with Jacobian of the measure wrt state
  215.         final ModifierGradientConverter converter =
  216.                 new ModifierGradientConverter(state, 6, new FrameAlignedProvider(state.getFrame()));
  217.         final FieldSpacecraftState<Gradient> gState = converter.getState(tropoModel);
  218.         final Gradient[] gParameters = converter.getParametersAtStateDate(gState, tropoModel);
  219.         final Gradient   primaryGDelay        = rangeErrorTroposphericModel(primaryStation, gState, gParameters);
  220.         final Gradient   secondaryGDelay      = rangeErrorTroposphericModel(secondaryStation, gState, gParameters);
  221.         final double[]   primaryDerivatives   = primaryGDelay.getGradient();
  222.         final double[]   secondaryDerivatives = secondaryGDelay.getGradient();

  224.         final double[][] primaryDjac      = rangeErrorJacobianState(primaryDerivatives);
  225.         final double[][] secondaryDjac    = rangeErrorJacobianState(secondaryDerivatives);
  226.         final double[][] stateDerivatives = estimated.getStateDerivatives(0);
  227.         for (int irow = 0; irow < stateDerivatives.length; ++irow) {
  228.             for (int jcol = 0; jcol < stateDerivatives[0].length; ++jcol) {
  229.                 stateDerivatives[irow][jcol] += primaryDjac[irow][jcol] + secondaryDjac[irow][jcol];
  230.             }
  231.         }
  232.         estimated.setStateDerivatives(0, stateDerivatives);

  234.         int indexPrimary = 0;
  235.         for (final ParameterDriver driver : getParametersDrivers()) {
  236.             if (driver.isSelected()) {
  237.                 // update estimated derivatives with derivative of the modification wrt tropospheric parameters
  238.                 for (Span<String> span = driver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {
  239.                     double parameterDerivative = estimated.getParameterDerivatives(driver, span.getStart())[0];
  240.                     final double[] derivatives = rangeErrorParameterDerivative(primaryDerivatives, converter.getFreeStateParameters());
  241.                     parameterDerivative += derivatives[indexPrimary];
  242.                     estimated.setParameterDerivatives(driver, span.getStart(), parameterDerivative);
  243.                     indexPrimary += 1;
  244.                 }
  245.             }

  247.         }

  249.         int indexSecondary = 0;
  250.         for (final ParameterDriver driver : getParametersDrivers()) {
  251.             if (driver.isSelected()) {
  252.                 // update estimated derivatives with derivative of the modification wrt tropospheric parameters
  253.                 for (Span<String> span = driver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {
  254.                     double parameterDerivative = estimated.getParameterDerivatives(driver, span.getStart())[0];
  255.                     final double[] derivatives = rangeErrorParameterDerivative(secondaryDerivatives, converter.getFreeStateParameters());
  256.                     parameterDerivative += derivatives[indexSecondary];
  257.                     estimated.setParameterDerivatives(driver, span.getStart(), parameterDerivative);
  258.                     indexSecondary += 1;
  259.                 }
  260.             }

  262.         }

  264.         // Update derivatives with respect to primary station position
  265.         for (final ParameterDriver driver : Arrays.asList(primaryStation.getClockOffsetDriver(),
  266.                                                           primaryStation.getEastOffsetDriver(),
  267.                                                           primaryStation.getNorthOffsetDriver(),
  268.                                                           primaryStation.getZenithOffsetDriver())) {
  269.             if (driver.isSelected()) {
  270.                 for (Span<String> span = driver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {

  272.                     double parameterDerivative = estimated.getParameterDerivatives(driver, span.getStart())[0];
  273.                     parameterDerivative += rangeErrorParameterDerivative(primaryStation, driver, state);
  274.                     estimated.setParameterDerivatives(driver, span.getStart(), parameterDerivative);
  275.                 }
  276.             }
  277.         }

  279.         // Update derivatives with respect to secondary station position
  280.         for (final ParameterDriver driver : Arrays.asList(secondaryStation.getEastOffsetDriver(),
  281.                                                           secondaryStation.getNorthOffsetDriver(),
  282.                                                           secondaryStation.getZenithOffsetDriver())) {
  283.             if (driver.isSelected()) {
  284.                 for (Span<String> span = driver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {

  286.                     double parameterDerivative = estimated.getParameterDerivatives(driver, span.getStart())[0];
  287.                     parameterDerivative += rangeErrorParameterDerivative(secondaryStation, driver, state);
  288.                     estimated.setParameterDerivatives(driver, span.getStart(), parameterDerivative);
  289.                 }
  290.             }
  291.         }

  293.         // Update estimated value taking into account the tropospheric delay.
  294.         // The tropospheric delay is directly added to the TurnAroundRange.
  295.         final double[] newValue = oldValue.clone();
  296.         newValue[0] = newValue[0] + primaryGDelay.getReal() + secondaryGDelay.getReal();
  297.         estimated.setEstimatedValue(newValue);

  299.     }

  301. }
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