Commit 4b6079b3 authored by Pascal Parraud's avatar Pascal Parraud
Browse files

Merge branch 'tdoa' into 'develop'

Tdoa

Closes #911

See merge request orekit/orekit!255
parents 4e797a80 10988521
......@@ -21,6 +21,9 @@
</properties>
<body>
<release version="11.2" date="TBD" description="TBD">
<action dev="pascal" type="add" issue="911">
Added TDOA and bistatic range rate measurements.
</action>
<action dev="bryan" type="fix" issue="910">
Fixed eD and eY equation in ECOM2 model.
</action>
......
/* Copyright 2002-2022 CS GROUP
* 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,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.orekit.estimation.measurements;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import org.hipparchus.analysis.differentiation.Gradient;
import org.hipparchus.analysis.differentiation.GradientField;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.orekit.frames.FieldTransform;
import org.orekit.propagation.SpacecraftState;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.utils.ParameterDriver;
import org.orekit.utils.TimeStampedFieldPVCoordinates;
import org.orekit.utils.TimeStampedPVCoordinates;
/** Class modeling a bistatic range rate measurement using
* an emitter ground station and a receiver ground station.
* <p>
* The measurement is considered to be a signal:
* <ul>
* <li>Emitted from the emitter ground station</li>
* <li>Reflected on the spacecraft</li>
* <li>Received on the receiver ground station</li>
* </ul>
* The date of the measurement corresponds to the reception on ground of the reflected signal.<br/>
* The quantity measured at the receiver is the bistatic radial velocity as the sum of the radial
* velocities with respect to the two stations.<br/>
* The motion of the stations and the spacecraft during the signal flight time are taken into account.<br/>
* The Doppler measurement can be obtained by multiplying the velocity by (fe/c), where
* fe is the emission frequency.
* </p>
*
* @author Pascal Parraud
* @since 11.2
*/
public class BistaticRangeRate extends AbstractMeasurement<BistaticRangeRate> {
/** Emitter ground station. */
private final GroundStation emitter;
/** Receiver ground station. */
private final GroundStation receiver;
/** Simple constructor.
* @param emitter emitter ground station
* @param receiver receiver ground station
* @param date date of the measurement
* @param rangeRate observed value, m/s
* @param sigma theoretical standard deviation
* @param baseWeight base weight
* @param satellite satellite related to this measurement
*/
public BistaticRangeRate(final GroundStation emitter, final GroundStation receiver,
final AbsoluteDate date, final double rangeRate, final double sigma,
final double baseWeight, final ObservableSatellite satellite) {
super(date, rangeRate, sigma, baseWeight, Collections.singletonList(satellite));
// add parameter drivers for the emitter, clock offset is not used
addParameterDriver(emitter.getEastOffsetDriver());
addParameterDriver(emitter.getNorthOffsetDriver());
addParameterDriver(emitter.getZenithOffsetDriver());
addParameterDriver(emitter.getPrimeMeridianOffsetDriver());
addParameterDriver(emitter.getPrimeMeridianDriftDriver());
addParameterDriver(emitter.getPolarOffsetXDriver());
addParameterDriver(emitter.getPolarDriftXDriver());
addParameterDriver(emitter.getPolarOffsetYDriver());
addParameterDriver(emitter.getPolarDriftYDriver());
// add parameter drivers for the receiver
addParameterDriver(receiver.getClockOffsetDriver());
addParameterDriver(receiver.getEastOffsetDriver());
addParameterDriver(receiver.getNorthOffsetDriver());
addParameterDriver(receiver.getZenithOffsetDriver());
addParameterDriver(receiver.getPrimeMeridianOffsetDriver());
addParameterDriver(receiver.getPrimeMeridianDriftDriver());
addParameterDriver(receiver.getPolarOffsetXDriver());
addParameterDriver(receiver.getPolarDriftXDriver());
addParameterDriver(receiver.getPolarOffsetYDriver());
addParameterDriver(receiver.getPolarDriftYDriver());
this.emitter = emitter;
this.receiver = receiver;
}
/** Get the emitter ground station.
* @return emitter ground station
*/
public GroundStation getEmitterStation() {
return emitter;
}
/** Get the receiver ground station.
* @return receiver ground station
*/
public GroundStation getReceiverStation() {
return receiver;
}
/** {@inheritDoc} */
@Override
protected EstimatedMeasurement<BistaticRangeRate> theoreticalEvaluation(final int iteration,
final int evaluation,
final SpacecraftState[] states) {
final SpacecraftState state = states[0];
// Bistatic range rate derivatives are computed with respect to:
// - Spacecraft state in inertial frame
// - Emitter station parameters
// - Receiver station parameters
// --------------------------
// - 0..2 - Position of the spacecraft in inertial frame
// - 3..5 - Velocity of the spacecraft in inertial frame
// - 6..n - stations' parameters (stations' offsets, pole, prime meridian...)
int nbParams = 6;
final Map<String, Integer> indices = new HashMap<String, Integer>();
for (ParameterDriver driver : getParametersDrivers()) {
// we have to check for duplicate keys because emitter and receiver stations share
// pole and prime meridian parameters names that must be considered
// as one set only (they are combined together by the estimation engine)
if (driver.isSelected() && !indices.containsKey(driver.getName())) {
indices.put(driver.getName(), nbParams++);
}
}
final FieldVector3D<Gradient> zero = FieldVector3D.getZero(GradientField.getField(nbParams));
// coordinates of the spacecraft as a gradient
final TimeStampedFieldPVCoordinates<Gradient> pvaG = getCoordinates(state, 0, nbParams);
// transform between receiver station frame and inertial frame
// at the real date of measurement, i.e. taking station clock offset into account
final FieldTransform<Gradient> receiverToInertial =
receiver.getOffsetToInertial(state.getFrame(), getDate(), nbParams, indices);
final FieldAbsoluteDate<Gradient> measurementDateG = receiverToInertial.getFieldDate();
// Receiver PV in inertial frame at the end of the downlink leg
final TimeStampedFieldPVCoordinates<Gradient> receiverPV =
receiverToInertial.transformPVCoordinates(new TimeStampedFieldPVCoordinates<>(measurementDateG,
zero, zero, zero));
// Compute propagation times
// (if state has already been set up to pre-compensate propagation delay,
// we will have delta == tauD and transitState will be the same as state)
// Downlink delay
final Gradient tauD = signalTimeOfFlight(pvaG, receiverPV.getPosition(), measurementDateG);
final Gradient delta = measurementDateG.durationFrom(state.getDate());
final Gradient deltaMTauD = delta.subtract(tauD);
// Transit state
final SpacecraftState transitState = state.shiftedBy(deltaMTauD.getValue());
// Transit PV
final TimeStampedFieldPVCoordinates<Gradient> transitPV = pvaG.shiftedBy(deltaMTauD);
// Downlink range-rate
final EstimatedMeasurement<BistaticRangeRate> evalDownlink =
oneWayTheoreticalEvaluation(iteration, evaluation, true,
receiverPV, transitPV, transitState, indices);
// transform between emitter station frame and inertial frame at the transit date
// clock offset from receiver is already compensated
final FieldTransform<Gradient> emitterToInertial =
emitter.getOffsetToInertial(state.getFrame(), transitPV.getDate(), nbParams, indices);
// emitter PV in inertial frame at the end of the uplink leg
final TimeStampedFieldPVCoordinates<Gradient> emitterPV =
emitterToInertial.transformPVCoordinates(new TimeStampedFieldPVCoordinates<>(transitPV.getDate(),
zero, zero, zero));
// Uplink delay
final Gradient tauU = signalTimeOfFlight(emitterPV, transitPV.getPosition(), transitPV.getDate());
// emitter position in inertial frame at the end of the uplink leg
final TimeStampedFieldPVCoordinates<Gradient> emitterUplink = emitterPV.shiftedBy(tauU.negate());
// Uplink range-rate
final EstimatedMeasurement<BistaticRangeRate> evalUplink =
oneWayTheoreticalEvaluation(iteration, evaluation, false,
emitterUplink, transitPV, transitState, indices);
// combine uplink and downlink values
final EstimatedMeasurement<BistaticRangeRate> estimated =
new EstimatedMeasurement<>(this, iteration, evaluation,
evalDownlink.getStates(),
new TimeStampedPVCoordinates[] {
evalUplink.getParticipants()[0],
evalDownlink.getParticipants()[0],
evalDownlink.getParticipants()[1]
});
estimated.setEstimatedValue(evalDownlink.getEstimatedValue()[0] + evalUplink.getEstimatedValue()[0]);
// combine uplink and downlink partial derivatives with respect to state
final double[][] sd1 = evalDownlink.getStateDerivatives(0);
final double[][] sd2 = evalUplink.getStateDerivatives(0);
final double[][] sd = new double[sd1.length][sd1[0].length];
for (int i = 0; i < sd.length; ++i) {
for (int j = 0; j < sd[0].length; ++j) {
sd[i][j] = sd1[i][j] + sd2[i][j];
}
}
estimated.setStateDerivatives(0, sd);
// combine uplink and downlink partial derivatives with respect to parameters
evalDownlink.getDerivativesDrivers().forEach(driver -> {
final double[] pd1 = evalDownlink.getParameterDerivatives(driver);
final double[] pd2 = evalUplink.getParameterDerivatives(driver);
final double[] pd = new double[pd1.length];
for (int i = 0; i < pd.length; ++i) {
pd[i] = pd1[i] + pd2[i];
}
estimated.setParameterDerivatives(driver, pd);
});
return estimated;
}
/** Evaluate range rate measurement in one-way.
* @param iteration iteration number
* @param evaluation evaluations counter
* @param downlink indicator for downlink leg
* @param stationPV station coordinates when signal is at station
* @param transitPV spacecraft coordinates at onboard signal transit
* @param transitState orbital state at onboard signal transit
* @param indices indices of the estimated parameters in derivatives computations
* @return theoretical value for the current leg
*/
private EstimatedMeasurement<BistaticRangeRate> oneWayTheoreticalEvaluation(final int iteration, final int evaluation, final boolean downlink,
final TimeStampedFieldPVCoordinates<Gradient> stationPV,
final TimeStampedFieldPVCoordinates<Gradient> transitPV,
final SpacecraftState transitState,
final Map<String, Integer> indices) {
// prepare the evaluation
final EstimatedMeasurement<BistaticRangeRate> estimated =
new EstimatedMeasurement<BistaticRangeRate>(this, iteration, evaluation,
new SpacecraftState[] {
transitState
}, new TimeStampedPVCoordinates[] {
(downlink ? transitPV : stationPV).toTimeStampedPVCoordinates(),
(downlink ? stationPV : transitPV).toTimeStampedPVCoordinates()
});
// range rate value
final FieldVector3D<Gradient> stationPosition = stationPV.getPosition();
final FieldVector3D<Gradient> relativePosition = stationPosition.subtract(transitPV.getPosition());
final FieldVector3D<Gradient> stationVelocity = stationPV.getVelocity();
final FieldVector3D<Gradient> relativeVelocity = stationVelocity.subtract(transitPV.getVelocity());
// radial direction
final FieldVector3D<Gradient> lineOfSight = relativePosition.normalize();
// range rate
final Gradient rangeRate = FieldVector3D.dotProduct(relativeVelocity, lineOfSight);
estimated.setEstimatedValue(rangeRate.getValue());
// compute partial derivatives of (rr) with respect to spacecraft state Cartesian coordinates
final double[] derivatives = rangeRate.getGradient();
estimated.setStateDerivatives(0, Arrays.copyOfRange(derivatives, 0, 6));
// set partial derivatives with respect to parameters
for (final ParameterDriver driver : getParametersDrivers()) {
final Integer index = indices.get(driver.getName());
if (index != null) {
estimated.setParameterDerivatives(driver, derivatives[index]);
}
}
return estimated;
}
}
/* Copyright 2002-2022 CS GROUP
* 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,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.orekit.estimation.measurements;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import org.hipparchus.analysis.differentiation.Gradient;
import org.hipparchus.analysis.differentiation.GradientField;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.hipparchus.util.FastMath;
import org.orekit.frames.FieldTransform;
import org.orekit.propagation.SpacecraftState;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.utils.Constants;
import org.orekit.utils.ParameterDriver;
import org.orekit.utils.TimeStampedFieldPVCoordinates;
import org.orekit.utils.TimeStampedPVCoordinates;
/** Class modeling a Time Difference of Arrival measurement with a satellite as emitter
* and two ground stations as receivers.
* <p>
* TDOA measures the difference in signal arrival time between the emitter and receivers,
* corresponding to a difference in ranges from the two receivers to the emitter.
* </p>
* <p>
* The date of the measurement corresponds to the reception of the signal by the prime station.<br/>
* The measurement corresponds to the date of the measurement minus
* the date of reception of the signal by the second station:
* <code>tdoa = tr<sub>1</sub> - tr<sub>2</sub></code>
* </p>
* <p>
* The motion of the stations and the satellite during the signal flight time are taken into account.
* </p>
* @author Pascal Parraud
* @since 11.2
*/
public class TDOA extends AbstractMeasurement<TDOA> {
/** Prime ground station, the one that gives the date of the measurement. */
private final GroundStation primeStation;
/** Second ground station, the one that gives the measurement, i.e. the delay. */
private final GroundStation secondStation;
/** Simple constructor.
* @param primeStation ground station that gives the date of the measurement
* @param secondStation ground station that gives the measurement
* @param date date of the measurement
* @param tdoa observed value (s)
* @param sigma theoretical standard deviation
* @param baseWeight base weight
* @param satellite satellite related to this measurement
*/
public TDOA(final GroundStation primeStation, final GroundStation secondStation,
final AbsoluteDate date, final double tdoa, final double sigma,
final double baseWeight, final ObservableSatellite satellite) {
super(date, tdoa, sigma, baseWeight, Collections.singletonList(satellite));
// add parameter drivers for the primary station
addParameterDriver(primeStation.getClockOffsetDriver());
addParameterDriver(primeStation.getEastOffsetDriver());
addParameterDriver(primeStation.getNorthOffsetDriver());
addParameterDriver(primeStation.getZenithOffsetDriver());
addParameterDriver(primeStation.getPrimeMeridianOffsetDriver());
addParameterDriver(primeStation.getPrimeMeridianDriftDriver());
addParameterDriver(primeStation.getPolarOffsetXDriver());
addParameterDriver(primeStation.getPolarDriftXDriver());
addParameterDriver(primeStation.getPolarOffsetYDriver());
addParameterDriver(primeStation.getPolarDriftYDriver());
// add parameter drivers for the secondary station
addParameterDriver(secondStation.getClockOffsetDriver());
addParameterDriver(secondStation.getEastOffsetDriver());
addParameterDriver(secondStation.getNorthOffsetDriver());
addParameterDriver(secondStation.getZenithOffsetDriver());
addParameterDriver(secondStation.getPrimeMeridianOffsetDriver());
addParameterDriver(secondStation.getPrimeMeridianDriftDriver());
addParameterDriver(secondStation.getPolarOffsetXDriver());
addParameterDriver(secondStation.getPolarDriftXDriver());
addParameterDriver(secondStation.getPolarOffsetYDriver());
addParameterDriver(secondStation.getPolarDriftYDriver());
this.primeStation = primeStation;
this.secondStation = secondStation;
}
/** Get the prime ground station, the one that gives the date of the measurement.
* @return prime ground station
*/
public GroundStation getPrimeStation() {
return primeStation;
}
/** Get the second ground station, the one that gives the measurement.
* @return second ground station
*/
public GroundStation getSecondStation() {
return secondStation;
}
/** {@inheritDoc} */
@Override
protected EstimatedMeasurement<TDOA> theoreticalEvaluation(final int iteration, final int evaluation,
final SpacecraftState[] states) {
final SpacecraftState state = states[0];
// TDOA derivatives are computed with respect to:
// - Spacecraft state in inertial frame
// - Prime station parameters
// - Second station parameters
// --------------------------
// - 0..2 - Position of the spacecraft in inertial frame
// - 3..5 - Velocity of the spacecraft in inertial frame
// - 6..n - stations' parameters (clock offset, station offsets, pole, prime meridian...)
int nbParams = 6;
final Map<String, Integer> indices = new HashMap<>();
for (ParameterDriver driver : getParametersDrivers()) {
// we have to check for duplicate keys because primary and secondary station share
// pole and prime meridian parameters names that must be considered
// as one set only (they are combined together by the estimation engine)
if (driver.isSelected() && !indices.containsKey(driver.getName())) {
indices.put(driver.getName(), nbParams++);
}
}
final FieldVector3D<Gradient> zero = FieldVector3D.getZero(GradientField.getField(nbParams));
// coordinates of the spacecraft as a gradient
final TimeStampedFieldPVCoordinates<Gradient> pvaG = getCoordinates(state, 0, nbParams);
// transform between prime station frame and inertial frame
// at the real date of measurement, i.e. taking station clock offset into account
final FieldTransform<Gradient> primeToInert =
primeStation.getOffsetToInertial(state.getFrame(), getDate(), nbParams, indices);
final FieldAbsoluteDate<Gradient> measurementDateG = primeToInert.getFieldDate();
// prime station PV in inertial frame at the real date of the measurement
final TimeStampedFieldPVCoordinates<Gradient> primePV =
primeToInert.transformPVCoordinates(new TimeStampedFieldPVCoordinates<>(measurementDateG,
zero, zero, zero));
// compute downlink delay from emitter to prime receiver
final Gradient tau1 = signalTimeOfFlight(pvaG, primePV.getPosition(), measurementDateG);
// elapsed time between state date and signal arrival to the prime receiver
final Gradient dtMtau1 = measurementDateG.durationFrom(state.getDate()).subtract(tau1);
// satellite state at signal emission
final SpacecraftState emitterState = state.shiftedBy(dtMtau1.getValue());
// satellite pv at signal emission (re)computed with gradient
final TimeStampedFieldPVCoordinates<Gradient> emitterPV = pvaG.shiftedBy(dtMtau1);
// second station PV in inertial frame at real date of signal reception
TimeStampedFieldPVCoordinates<Gradient> secondPV;
// initialize search loop of the reception date by second station
Gradient tau2 = tau1;
double delta;
int count = 0;
do {
final double previous = tau2.getValue();
// date of signal arrival on second receiver
final AbsoluteDate dateAt2 = emitterState.getDate().shiftedBy(previous);
// transform between second station frame and inertial frame
// at the date of signal arrival, taking clock offset into account
final FieldTransform<Gradient> secondToInert =
secondStation.getOffsetToInertial(state.getFrame(), dateAt2,
nbParams, indices);
// second receiver position in inertial frame at the real date of signal reception
secondPV = secondToInert.transformPVCoordinates(new TimeStampedFieldPVCoordinates<>(secondToInert.getFieldDate(),
zero, zero, zero));
// downlink delay from emitter to second receiver
tau2 = linkDelay(emitterPV.getPosition(), secondPV.getPosition());
// Change in the computed downlink delay
delta = FastMath.abs(tau2.getValue() - previous);
} while (count++ < 10 && delta >= 2 * FastMath.ulp(tau2.getValue()));
// The measured TDOA is (tau1 + clockOffset1) - (tau2 + clockOffset2)
final Gradient offset1 = primeStation.getClockOffsetDriver().getValue(nbParams, indices);
final Gradient offset2 = secondStation.getClockOffsetDriver().getValue(nbParams, indices);
final Gradient tdoaG = tau1.add(offset1).subtract(tau2.add(offset2));
final double tdoa = tdoaG.getValue();
// Evaluate the TDOA value and derivatives
// -------------------------------------------
final TimeStampedPVCoordinates pv1 = primePV.toTimeStampedPVCoordinates();
final TimeStampedPVCoordinates pv2 = secondPV.toTimeStampedPVCoordinates();
final EstimatedMeasurement<TDOA> estimated =
new EstimatedMeasurement<>(this, iteration, evaluation,
new SpacecraftState[] {
emitterState
},
new TimeStampedPVCoordinates[] {
emitterPV.toTimeStampedPVCoordinates(),
tdoa > 0 ? pv2 : pv1,
tdoa > 0 ? pv1 : pv2
});
// set TDOA value
estimated.setEstimatedValue(tdoa);
// set partial derivatives with respect to state
final double[] derivatives = tdoaG.getGradient();
estimated.setStateDerivatives(0, Arrays.copyOfRange(derivatives, 0, 6));
// set partial derivatives with respect to parameters
for (final ParameterDriver driver : getParametersDrivers()) {
final Integer index = indices.get(driver.getName());
if (index != null) {
estimated.setParameterDerivatives(driver, derivatives[index]);
}
}
return estimated;
}
/** Compute propagation delay on a link.
* @param emitter the position of the emitter
* @param receiver the position of the receiver (same frame as emitter)
* @return the propagation delay
*/
private Gradient linkDelay(final FieldVector3D<Gradient> emitter,
final FieldVector3D<Gradient> receiver) {
return receiver.distance(emitter).divide(Constants.SPEED_OF_LIGHT);
}
}
/* Copyright 2002-2022 CS GROUP
* 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,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.orekit.estimation.measurements.generation;
import org.hipparchus.random.CorrelatedRandomVectorGenerator;
import org.orekit.estimation.measurements.BistaticRangeRate;
import org.orekit.estimation.measurements.EstimationModifier;
import org.orekit.estimation.measurements.GroundStation;
import org.orekit.estimation.measurements.ObservableSatellite;
import org.orekit.propagation.SpacecraftState;
import org.orekit.time.AbsoluteDate;
import org.orekit.utils.ParameterDriver;