AbstractMeasurement.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;

  19. import java.util.ArrayList;
  20. import java.util.Collections;
  21. import java.util.List;

  23. import org.hipparchus.CalculusFieldElement;
  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.hipparchus.util.FastMath;
  28. import org.orekit.propagation.SpacecraftState;
  29. import org.orekit.time.AbsoluteDate;
  30. import org.orekit.time.FieldAbsoluteDate;
  31. import org.orekit.utils.Constants;
  32. import org.orekit.utils.ParameterDriver;
  33. import org.orekit.utils.TimeStampedFieldPVCoordinates;
  34. import org.orekit.utils.TimeStampedPVCoordinates;

  36. /** Abstract class handling measurements boilerplate.
  37.  * @param <T> the type of the measurement
  38.  * @author Luc Maisonobe
  39.  * @since 8.0
  40.  */
  41. public abstract class AbstractMeasurement<T extends ObservedMeasurement<T>> implements ObservedMeasurement<T> {

  43.     /** List of the supported parameters. */
  44.     private final List<ParameterDriver> supportedParameters;

  46.     /** Satellites related to this measurement.
  47.      * @since 9.3
  48.      */
  49.     private final List<ObservableSatellite> satellites;

  51.     /** Date of the measurement. */
  52.     private final AbsoluteDate date;

  54.     /** Observed value. */
  55.     private final double[] observed;

  57.     /** Theoretical standard deviation. */
  58.     private final double[] sigma;

  60.     /** Base weight. */
  61.     private final double[] baseWeight;

  63.     /** Modifiers that apply to the measurement.*/
  64.     private final List<EstimationModifier<T>> modifiers;

  66.     /** Enabling status. */
  67.     private boolean enabled;

  69.     /** Simple constructor for mono-dimensional measurements.
  70.      * <p>
  71.      * At construction, a measurement is enabled.
  72.      * </p>
  73.      * @param date date of the measurement
  74.      * @param observed observed value
  75.      * @param sigma theoretical standard deviation
  76.      * @param baseWeight base weight
  77.      * @param satellites satellites related to this measurement
  78.      * @since 9.3
  79.      */
  80.     protected AbstractMeasurement(final AbsoluteDate date, final double observed,
  81.                                   final double sigma, final double baseWeight,
  82.                                   final List<ObservableSatellite> satellites) {

  84.         this.supportedParameters = new ArrayList<ParameterDriver>();

  86.         this.date       = date;
  87.         this.observed   = new double[] {
  88.             observed
  89.         };
  90.         this.sigma      = new double[] {
  91.             sigma
  92.         };
  93.         this.baseWeight = new double[] {
  94.             baseWeight
  95.         };

  97.         this.satellites = satellites;

  99.         this.modifiers = new ArrayList<EstimationModifier<T>>();
  100.         setEnabled(true);

  102.     }

  104.     /** Simple constructor, for multi-dimensional measurements.
  105.      * <p>
  106.      * At construction, a measurement is enabled.
  107.      * </p>
  108.      * @param date date of the measurement
  109.      * @param observed observed value
  110.      * @param sigma theoretical standard deviation
  111.      * @param baseWeight base weight
  112.      * @param satellites satellites related to this measurement
  113.      * @since 9.3
  114.      */
  115.     protected AbstractMeasurement(final AbsoluteDate date, final double[] observed,
  116.                                   final double[] sigma, final double[] baseWeight,
  117.                                   final List<ObservableSatellite> satellites) {
  118.         this.supportedParameters = new ArrayList<ParameterDriver>();

  120.         this.date       = date;
  121.         this.observed   = observed.clone();
  122.         this.sigma      = sigma.clone();
  123.         this.baseWeight = baseWeight.clone();

  125.         this.satellites = satellites;

  127.         this.modifiers = new ArrayList<EstimationModifier<T>>();
  128.         setEnabled(true);

  130.     }

  132.     /** Add a parameter driver.
  133.      * @param driver parameter driver to add
  134.      * @since 9.3
  135.      */
  136.     protected void addParameterDriver(final ParameterDriver driver) {
  137.         supportedParameters.add(driver);
  138.     }

  140.     /** {@inheritDoc} */
  141.     @Override
  142.     public List<ParameterDriver> getParametersDrivers() {
  143.         return Collections.unmodifiableList(supportedParameters);
  144.     }

  146.     /** {@inheritDoc} */
  147.     @Override
  148.     public void setEnabled(final boolean enabled) {
  149.         this.enabled = enabled;
  150.     }

  152.     /** {@inheritDoc} */
  153.     @Override
  154.     public boolean isEnabled() {
  155.         return enabled;
  156.     }

  158.     /** {@inheritDoc} */
  159.     @Override
  160.     public int getDimension() {
  161.         return observed.length;
  162.     }

  164.     /** {@inheritDoc} */
  165.     @Override
  166.     public double[] getTheoreticalStandardDeviation() {
  167.         return sigma.clone();
  168.     }

  170.     /** {@inheritDoc} */
  171.     @Override
  172.     public double[] getBaseWeight() {
  173.         return baseWeight.clone();
  174.     }

  176.     /** {@inheritDoc} */
  177.     @Override
  178.     public List<ObservableSatellite> getSatellites() {
  179.         return satellites;
  180.     }

  182.     /** Estimate the theoretical value without derivatives.
  183.      * <p>
  184.      * The theoretical value does not have <em>any</em> modifiers applied.
  185.      * </p>
  186.      * @param iteration iteration number
  187.      * @param evaluation evaluation number
  188.      * @param states orbital states at measurement date
  189.      * @return theoretical value
  190.      * @see #estimate(int, int, SpacecraftState[])
  191.      * @since 12.0
  192.      */
  193.     protected abstract EstimatedMeasurementBase<T> theoreticalEvaluationWithoutDerivatives(int iteration, int evaluation,
  194.                                                                                            SpacecraftState[] states);

  196.     /** Estimate the theoretical value.
  197.      * <p>
  198.      * The theoretical value does not have <em>any</em> modifiers applied.
  199.      * </p>
  200.      * @param iteration iteration number
  201.      * @param evaluation evaluation number
  202.      * @param states orbital states at measurement date
  203.      * @return theoretical value
  204.      * @see #estimate(int, int, SpacecraftState[])
  205.      */
  206.     protected abstract EstimatedMeasurement<T> theoreticalEvaluation(int iteration, int evaluation, SpacecraftState[] states);

  208.     /** {@inheritDoc} */
  209.     @Override
  210.     public EstimatedMeasurementBase<T> estimateWithoutDerivatives(final int iteration, final int evaluation, final SpacecraftState[] states) {

  212.         // compute the theoretical value
  213.         final EstimatedMeasurementBase<T> estimation = theoreticalEvaluationWithoutDerivatives(iteration, evaluation, states);

  215.         // apply the modifiers
  216.         for (final EstimationModifier<T> modifier : modifiers) {
  217.             modifier.modifyWithoutDerivatives(estimation);
  218.         }

  220.         return estimation;

  222.     }

  224.     /** {@inheritDoc} */
  225.     @Override
  226.     public EstimatedMeasurement<T> estimate(final int iteration, final int evaluation, final SpacecraftState[] states) {

  228.         // compute the theoretical value
  229.         final EstimatedMeasurement<T> estimation = theoreticalEvaluation(iteration, evaluation, states);

  231.         // apply the modifiers
  232.         for (final EstimationModifier<T> modifier : modifiers) {
  233.             modifier.modify(estimation);
  234.         }

  236.         return estimation;

  238.     }

  240.     /** {@inheritDoc} */
  241.     @Override
  242.     public AbsoluteDate getDate() {
  243.         return date;
  244.     }

  246.     /** {@inheritDoc} */
  247.     @Override
  248.     public double[] getObservedValue() {
  249.         return observed.clone();
  250.     }

  252.     /** {@inheritDoc} */
  253.     @Override
  254.     public void addModifier(final EstimationModifier<T> modifier) {

  256.         // combine the measurement parameters and the modifier parameters
  257.         supportedParameters.addAll(modifier.getParametersDrivers());

  259.         modifiers.add(modifier);

  261.     }

  263.     /** {@inheritDoc} */
  264.     @Override
  265.     public List<EstimationModifier<T>> getModifiers() {
  266.         return Collections.unmodifiableList(modifiers);
  267.     }

  269.     /** Compute propagation delay on a link leg (typically downlink or uplink).
  270.      * @param adjustableEmitterPV position/velocity of emitter that may be adjusted
  271.      * @param receiverPosition fixed position of receiver at {@code signalArrivalDate},
  272.      * in the same frame as {@code adjustableEmitterPV}
  273.      * @param signalArrivalDate date at which the signal arrives to receiver
  274.      * @return <em>positive</em> delay between signal emission and signal reception dates
  275.      */
  276.     public static double signalTimeOfFlight(final TimeStampedPVCoordinates adjustableEmitterPV,
  277.                                             final Vector3D receiverPosition,
  278.                                             final AbsoluteDate signalArrivalDate) {

  280.         // initialize emission date search loop assuming the state is already correct
  281.         // this will be true for all but the first orbit determination iteration,
  282.         // and even for the first iteration the loop will converge very fast
  283.         final double offset = signalArrivalDate.durationFrom(adjustableEmitterPV.getDate());
  284.         double delay = offset;

  286.         // search signal transit date, computing the signal travel in inertial frame
  287.         final double cReciprocal = 1.0 / Constants.SPEED_OF_LIGHT;
  288.         double delta;
  289.         int count = 0;
  290.         do {
  291.             final double previous   = delay;
  292.             final Vector3D transitP = adjustableEmitterPV.shiftedBy(offset - delay).getPosition();
  293.             delay                   = receiverPosition.distance(transitP) * cReciprocal;
  294.             delta                   = FastMath.abs(delay - previous);
  295.         } while (count++ < 10 && delta >= 2 * FastMath.ulp(delay));

  297.         return delay;

  299.     }

  301.     /** Compute propagation delay on a link leg (typically downlink or uplink).
  302.      * @param adjustableEmitterPV position/velocity of emitter that may be adjusted
  303.      * @param receiverPosition fixed position of receiver at {@code signalArrivalDate},
  304.      * in the same frame as {@code adjustableEmitterPV}
  305.      * @param signalArrivalDate date at which the signal arrives to receiver
  306.      * @return <em>positive</em> delay between signal emission and signal reception dates
  307.      * @param <T> the type of the components
  308.      */
  309.     public static <T extends CalculusFieldElement<T>> T signalTimeOfFlight(final TimeStampedFieldPVCoordinates<T> adjustableEmitterPV,
  310.                                                                            final FieldVector3D<T> receiverPosition,
  311.                                                                            final FieldAbsoluteDate<T> signalArrivalDate) {

  313.         // Initialize emission date search loop assuming the emitter PV is almost correct
  314.         // this will be true for all but the first orbit determination iteration,
  315.         // and even for the first iteration the loop will converge extremely fast
  316.         final T offset = signalArrivalDate.durationFrom(adjustableEmitterPV.getDate());
  317.         T delay = offset;

  319.         // search signal transit date, computing the signal travel in the frame shared by emitter and receiver
  320.         final double cReciprocal = 1.0 / Constants.SPEED_OF_LIGHT;
  321.         double delta;
  322.         int count = 0;
  323.         do {
  324.             final double previous           = delay.getReal();
  325.             final FieldVector3D<T> transitP = adjustableEmitterPV.shiftedBy(delay.negate().add(offset)).getPosition();
  326.             delay                           = receiverPosition.distance(transitP).multiply(cReciprocal);
  327.             delta                           = FastMath.abs(delay.getReal() - previous);
  328.         } while (count++ < 10 && delta >= 2 * FastMath.ulp(delay.getReal()));

  330.         return delay;

  332.     }

  334.     /** Get Cartesian coordinates as derivatives.
  335.      * <p>
  336.      * The position will correspond to variables {@code firstDerivative},
  337.      * {@code firstDerivative + 1} and {@code firstDerivative + 2}.
  338.      * The velocity will correspond to variables {@code firstDerivative + 3},
  339.      * {@code firstDerivative + 4} and {@code firstDerivative + 5}.
  340.      * The acceleration will correspond to constants.
  341.      * </p>
  342.      * @param state state of the satellite considered
  343.      * @param firstDerivative index of the first derivative
  344.      * @param freeParameters total number of free parameters in the gradient
  345.      * @return Cartesian coordinates as derivatives
  346.      * @since 10.2
  347.      */
  348.     public static TimeStampedFieldPVCoordinates<Gradient> getCoordinates(final SpacecraftState state,
  349.                                                                          final int firstDerivative,
  350.                                                                          final int freeParameters) {

  352.         // Position of the satellite expressed as a gradient
  353.         // The components of the position are the 3 first derivative parameters
  354.         final Vector3D p = state.getPosition();
  355.         final FieldVector3D<Gradient> pDS =
  356.                         new FieldVector3D<>(Gradient.variable(freeParameters, firstDerivative + 0, p.getX()),
  357.                                             Gradient.variable(freeParameters, firstDerivative + 1, p.getY()),
  358.                                             Gradient.variable(freeParameters, firstDerivative + 2, p.getZ()));

  360.         // Velocity of the satellite expressed as a gradient
  361.         // The components of the velocity are the 3 second derivative parameters
  362.         final Vector3D v = state.getPVCoordinates().getVelocity();
  363.         final FieldVector3D<Gradient> vDS =
  364.                         new FieldVector3D<>(Gradient.variable(freeParameters, firstDerivative + 3, v.getX()),
  365.                                             Gradient.variable(freeParameters, firstDerivative + 4, v.getY()),
  366.                                             Gradient.variable(freeParameters, firstDerivative + 5, v.getZ()));

  368.         // Acceleration of the satellite
  369.         // The components of the acceleration are not derivative parameters
  370.         final Vector3D a = state.getPVCoordinates().getAcceleration();
  371.         final FieldVector3D<Gradient> aDS =
  372.                         new FieldVector3D<>(Gradient.constant(freeParameters, a.getX()),
  373.                                             Gradient.constant(freeParameters, a.getY()),
  374.                                             Gradient.constant(freeParameters, a.getZ()));

  376.         return new TimeStampedFieldPVCoordinates<>(state.getDate(), pDS, vDS, aDS);

  378.     }

  380. }
Created with JaCoCo 0.8.11.202310140853