InterSatellitesOneWayRangeRate.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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* See the License for the specific language governing permissions and
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*/
package org.orekit.estimation.measurements.gnss;
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.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.ParameterDriver;
import org.orekit.utils.TimeSpanMap.Span;
import org.orekit.utils.TimeStampedPVCoordinates;
import java.util.Arrays;
/** One way range-rate measurement between two satellites.
* @author Luc Maisonobe
* @since 12.1
*/
public class InterSatellitesOneWayRangeRate
extends AbstractInterSatellitesMeasurement<InterSatellitesOneWayRangeRate> {
/** Type of the measurement. */
public static final String MEASUREMENT_TYPE = "InterSatellitesOneWayRangeRate";
/** Constructor.
* @param local satellite which receives the signal and performs the measurement
* @param remote remote satellite which simply emits the signal
* @param date date of the measurement
* @param rangeRate observed value (m/s)
* @param sigma theoretical standard deviation
* @param baseWeight base weight
*/
public InterSatellitesOneWayRangeRate(final ObservableSatellite local,
final ObservableSatellite remote,
final AbsoluteDate date, final double rangeRate,
final double sigma, final double baseWeight) {
// Call to super constructor
super(date, rangeRate, sigma, baseWeight, local, remote);
}
/** {@inheritDoc} */
@Override
protected EstimatedMeasurementBase<InterSatellitesOneWayRangeRate> theoreticalEvaluationWithoutDerivatives(final int iteration,
final int evaluation,
final SpacecraftState[] states) {
final OnBoardCommonParametersWithoutDerivatives common = computeCommonParametersWithout(states, false);
// prepare the evaluation
final EstimatedMeasurementBase<InterSatellitesOneWayRangeRate> estimatedPhase =
new EstimatedMeasurementBase<>(this, iteration, evaluation,
new SpacecraftState[] {
common.getState(),
states[1]
}, 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());
estimatedPhase.setEstimatedValue(rangeRate);
// Return the estimated measurement
return estimatedPhase;
}
/** {@inheritDoc} */
@Override
protected EstimatedMeasurement<InterSatellitesOneWayRangeRate> theoreticalEvaluation(final int iteration,
final int evaluation,
final SpacecraftState[] states) {
final OnBoardCommonParametersWithDerivatives common = computeCommonParametersWith(states, false);
// prepare the evaluation
final EstimatedMeasurement<InterSatellitesOneWayRangeRate> estimatedPhase =
new EstimatedMeasurement<>(this, iteration, evaluation,
new SpacecraftState[] {
common.getState(),
states[1]
}, 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));
estimatedPhase.setEstimatedValue(rangeRate.getValue());
// Range first order derivatives with respect to states
final double[] derivatives = rangeRate.getGradient();
estimatedPhase.setStateDerivatives(0, Arrays.copyOfRange(derivatives, 0, 6));
estimatedPhase.setStateDerivatives(1, Arrays.copyOfRange(derivatives, 6, 12));
// Set first order derivatives with respect to parameters
for (final ParameterDriver driver : getParametersDrivers()) {
for (Span<String> span = driver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {
final Integer index = common.getIndices().get(span.getData());
if (index != null) {
estimatedPhase.setParameterDerivatives(driver, span.getStart(), derivatives[index]);
}
}
}
// Return the estimated measurement
return estimatedPhase;
}
}