OneWayGNSSRangeRate.java
/* Copyright 2002-2024 Thales Alenia Space
* Licensed to CS GROUP (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
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*/
package org.orekit.estimation.measurements.gnss;
import java.util.Arrays;
import org.hipparchus.analysis.differentiation.Gradient;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.orekit.estimation.measurements.EstimatedMeasurement;
import org.orekit.estimation.measurements.EstimatedMeasurementBase;
import org.orekit.estimation.measurements.ObservableSatellite;
import org.orekit.estimation.measurements.QuadraticClockModel;
import org.orekit.propagation.SpacecraftState;
import org.orekit.time.AbsoluteDate;
import org.orekit.utils.Constants;
import org.orekit.utils.FieldPVCoordinates;
import org.orekit.utils.PVCoordinates;
import org.orekit.utils.PVCoordinatesProvider;
import org.orekit.utils.ParameterDriver;
import org.orekit.utils.TimeSpanMap.Span;
import org.orekit.utils.TimeStampedPVCoordinates;
/** One-way GNSS range rate measurement.
* <p>
* This class can be used in precise orbit determination applications
* for modeling a range rate measurement between a GNSS satellite (emitter)
* and a LEO satellite (receiver).
* <p>
* The one-way GNSS range rate measurement assumes knowledge of the orbit and
* the clock offset of the emitting GNSS satellite. For instance, it is
* possible to use a SP3 file or a GNSS navigation message to recover
* the satellite's orbit and clock.
* <p>
* This class is very similar to {@link InterSatellitesOneWayRangeRate} measurement
* class. However, using the one-way GNSS range measurement, the orbit and clock
* of the emitting GNSS satellite are <b>NOT</b> estimated simultaneously with
* LEO satellite coordinates.
*
* @author Luc Maisonobe
* @since 12.1
*/
public class OneWayGNSSRangeRate extends AbstractOneWayGNSSMeasurement<OneWayGNSSRangeRate> {
/** Type of the measurement. */
public static final String MEASUREMENT_TYPE = "OneWayGNSSRangeRate";
/** Simple constructor.
* @param remote provider for GNSS satellite which simply emits the signal
* @param dtRemote clock offset of the GNSS satellite, in seconds
* @param date date of the measurement
* @param rangeRate observed value
* @param sigma theoretical standard deviation
* @param baseWeight base weight
* @param local satellite which receives the signal and perform the measurement
*/
public OneWayGNSSRangeRate(final PVCoordinatesProvider remote,
final double dtRemote,
final AbsoluteDate date,
final double rangeRate, final double sigma,
final double baseWeight, final ObservableSatellite local) {
this(remote, new QuadraticClockModel(date, dtRemote, 0.0, 0.0), date, rangeRate, sigma, baseWeight, local);
}
/** Simple constructor.
* @param remote provider for GNSS satellite which simply emits the signal
* @param remoteClock clock offset of the GNSS satellite
* @param date date of the measurement
* @param rangeRate observed value
* @param sigma theoretical standard deviation
* @param baseWeight base weight
* @param local satellite which receives the signal and perform the measurement
* @since 12.1
*/
public OneWayGNSSRangeRate(final PVCoordinatesProvider remote,
final QuadraticClockModel remoteClock,
final AbsoluteDate date,
final double rangeRate, final double sigma,
final double baseWeight, final ObservableSatellite local) {
// Call super constructor
super(remote, remoteClock, date, rangeRate, sigma, baseWeight, local);
}
/** {@inheritDoc} */
@Override
protected EstimatedMeasurementBase<OneWayGNSSRangeRate> theoreticalEvaluationWithoutDerivatives(final int iteration,
final int evaluation,
final SpacecraftState[] states) {
final OnBoardCommonParametersWithoutDerivatives common = computeCommonParametersWithout(states, false);
// Estimated measurement
final EstimatedMeasurementBase<OneWayGNSSRangeRate> estimatedRangeRate =
new EstimatedMeasurementBase<>(this, iteration, evaluation,
new SpacecraftState[] {
common.getState()
}, new TimeStampedPVCoordinates[] {
common.getRemotePV(),
common.getTransitPV()
});
// Range rate value
final PVCoordinates delta = new PVCoordinates(common.getRemotePV(), common.getTransitPV());
final double rangeRate = Vector3D.dotProduct(delta.getVelocity(), delta.getPosition().normalize()) +
Constants.SPEED_OF_LIGHT * (common.getLocalRate() - common.getRemoteRate());
// Set value of the estimated measurement
estimatedRangeRate.setEstimatedValue(rangeRate);
// Return the estimated measurement
return estimatedRangeRate;
}
/** {@inheritDoc} */
@Override
protected EstimatedMeasurement<OneWayGNSSRangeRate> theoreticalEvaluation(final int iteration,
final int evaluation,
final SpacecraftState[] states) {
final OnBoardCommonParametersWithDerivatives common = computeCommonParametersWith(states, false);
// Estimated measurement
final EstimatedMeasurement<OneWayGNSSRangeRate> estimatedRangeRate =
new EstimatedMeasurement<>(this, iteration, evaluation,
new SpacecraftState[] {
common.getState()
}, new TimeStampedPVCoordinates[] {
common.getRemotePV().toTimeStampedPVCoordinates(),
common.getTransitPV().toTimeStampedPVCoordinates()
});
// Range rate value
final FieldPVCoordinates<Gradient> delta = new FieldPVCoordinates<>(common.getRemotePV(), common.getTransitPV());
final Gradient rangeRate = FieldVector3D.dotProduct(delta.getVelocity(), delta.getPosition().normalize()).
add(common.getLocalRate().subtract(common.getRemoteRate()).multiply(Constants.SPEED_OF_LIGHT));
final double[] rangeRateDerivatives = rangeRate.getGradient();
// Set value and state first order derivatives of the estimated measurement
estimatedRangeRate.setEstimatedValue(rangeRate.getValue());
estimatedRangeRate.setStateDerivatives(0, Arrays.copyOfRange(rangeRateDerivatives, 0, 6));
// Set first order derivatives with respect to parameters
for (final ParameterDriver measurementDriver : getParametersDrivers()) {
for (Span<String> span = measurementDriver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {
final Integer index = common.getIndices().get(span.getData());
if (index != null) {
estimatedRangeRate.setParameterDerivatives(measurementDriver, span.getStart(), rangeRateDerivatives[index]);
}
}
}
// Return the estimated measurement
return estimatedRangeRate;
}
}