GroundReceiverMeasurement.java
/* Copyright 2002-2023 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.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.geometry.euclidean.threed.Vector3D;
import org.orekit.frames.FieldTransform;
import org.orekit.frames.Frame;
import org.orekit.frames.Transform;
import org.orekit.propagation.SpacecraftState;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.utils.PVCoordinates;
import org.orekit.utils.ParameterDriver;
import org.orekit.utils.TimeSpanMap.Span;
import org.orekit.utils.TimeStampedFieldPVCoordinates;
import org.orekit.utils.TimeStampedPVCoordinates;
/** Base class modeling a measurement where receiver is a ground station.
* @author Thierry Ceolin
* @author Luc Maisonobe
* @author Maxime Journot
* @since 12.0
* @param <T> type of the measurement
*/
public abstract class GroundReceiverMeasurement<T extends GroundReceiverMeasurement<T>> extends AbstractMeasurement<T> {
/** Ground station from which measurement is performed. */
private final GroundStation station;
/** Flag indicating whether it is a two-way measurement. */
private final boolean twoway;
/** Simple constructor.
* @param station ground station from which measurement is performed
* @param twoWay flag indicating whether it is a two-way measurement
* @param date date of the measurement
* @param observed observed value
* @param sigma theoretical standard deviation
* @param baseWeight base weight
* @param satellite satellite related to this measurement
*/
public GroundReceiverMeasurement(final GroundStation station, final boolean twoWay, final AbsoluteDate date,
final double observed, final double sigma, final double baseWeight,
final ObservableSatellite satellite) {
super(date, observed, sigma, baseWeight, Collections.singletonList(satellite));
addParameterDriver(station.getClockOffsetDriver());
addParameterDriver(station.getClockDriftDriver());
addParameterDriver(station.getEastOffsetDriver());
addParameterDriver(station.getNorthOffsetDriver());
addParameterDriver(station.getZenithOffsetDriver());
addParameterDriver(station.getPrimeMeridianOffsetDriver());
addParameterDriver(station.getPrimeMeridianDriftDriver());
addParameterDriver(station.getPolarOffsetXDriver());
addParameterDriver(station.getPolarDriftXDriver());
addParameterDriver(station.getPolarOffsetYDriver());
addParameterDriver(station.getPolarDriftYDriver());
if (!twoWay) {
// for one way measurements, the satellite clock offset affects the measurement
addParameterDriver(satellite.getClockOffsetDriver());
addParameterDriver(satellite.getClockDriftDriver());
}
this.station = station;
this.twoway = twoWay;
}
/** Simple constructor.
* @param station ground station from which measurement is performed
* @param twoWay flag indicating whether it is a two-way measurement
* @param date date of the measurement
* @param observed observed value
* @param sigma theoretical standard deviation
* @param baseWeight base weight
* @param satellite satellite related to this measurement
*/
public GroundReceiverMeasurement(final GroundStation station, final boolean twoWay, final AbsoluteDate date,
final double[] observed, final double[] sigma, final double[] baseWeight,
final ObservableSatellite satellite) {
super(date, observed, sigma, baseWeight, Collections.singletonList(satellite));
addParameterDriver(station.getClockOffsetDriver());
addParameterDriver(station.getClockDriftDriver());
addParameterDriver(station.getEastOffsetDriver());
addParameterDriver(station.getNorthOffsetDriver());
addParameterDriver(station.getZenithOffsetDriver());
addParameterDriver(station.getPrimeMeridianOffsetDriver());
addParameterDriver(station.getPrimeMeridianDriftDriver());
addParameterDriver(station.getPolarOffsetXDriver());
addParameterDriver(station.getPolarDriftXDriver());
addParameterDriver(station.getPolarOffsetYDriver());
addParameterDriver(station.getPolarDriftYDriver());
if (!twoWay) {
// for one way measurements, the satellite clock offset affects the measurement
addParameterDriver(satellite.getClockOffsetDriver());
addParameterDriver(satellite.getClockDriftDriver());
}
this.station = station;
this.twoway = twoWay;
}
/** Get the ground station from which measurement is performed.
* @return ground station from which measurement is performed
*/
public GroundStation getStation() {
return station;
}
/** Check if the instance represents a two-way measurement.
* @return true if the instance represents a two-way measurement
*/
public boolean isTwoWay() {
return twoway;
}
/** Compute common estimation parameters.
* @param state orbital state at measurement date
* @return common parameters
*/
protected GroundReceiverCommonParametersWithoutDerivatives computeCommonParametersWithout(final SpacecraftState state) {
// Coordinates of the spacecraft
final TimeStampedPVCoordinates pva = state.getPVCoordinates();
// transform between station and inertial frame
final Transform offsetToInertialDownlink =
getStation().getOffsetToInertial(state.getFrame(), getDate(), false);
final AbsoluteDate downlinkDate = offsetToInertialDownlink.getDate();
// Station position in inertial frame at end of the downlink leg
final TimeStampedPVCoordinates origin = new TimeStampedPVCoordinates(downlinkDate,
Vector3D.ZERO, Vector3D.ZERO, Vector3D.ZERO);
final TimeStampedPVCoordinates stationDownlink = offsetToInertialDownlink.transformPVCoordinates(origin);
// 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 double tauD = signalTimeOfFlight(pva, stationDownlink.getPosition(), downlinkDate);
// Transit state & Transit state (re)computed with gradients
final double delta = downlinkDate.durationFrom(state.getDate());
final double deltaMTauD = delta - tauD;
final SpacecraftState transitState = state.shiftedBy(deltaMTauD);
return new GroundReceiverCommonParametersWithoutDerivatives(state,
offsetToInertialDownlink,
stationDownlink,
tauD,
transitState,
transitState.getPVCoordinates());
}
/** Compute common estimation parameters.
* @param state orbital state at measurement date
* @return common parameters
*/
protected GroundReceiverCommonParametersWithDerivatives computeCommonParametersWithDerivatives(final SpacecraftState state) {
int nbParams = 6;
final Map<String, Integer> indices = new HashMap<>();
for (ParameterDriver driver : getParametersDrivers()) {
if (driver.isSelected()) {
for (Span<String> span = driver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {
indices.put(span.getData(), nbParams++);
}
}
}
final FieldVector3D<Gradient> zero = FieldVector3D.getZero(GradientField.getField(nbParams));
// Coordinates of the spacecraft expressed as a gradient
final TimeStampedFieldPVCoordinates<Gradient> pva = getCoordinates(state, 0, nbParams);
// transform between station and inertial frame, expressed as a gradient
// The components of station's position in offset frame are the 3 last derivative parameters
final FieldTransform<Gradient> offsetToInertialDownlink =
getStation().getOffsetToInertial(state.getFrame(), getDate(), nbParams, indices);
final FieldAbsoluteDate<Gradient> downlinkDate = offsetToInertialDownlink.getFieldDate();
// Station position in inertial frame at end of the downlink leg
final TimeStampedFieldPVCoordinates<Gradient> stationDownlink =
offsetToInertialDownlink.transformPVCoordinates(new TimeStampedFieldPVCoordinates<>(downlinkDate,
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(pva, stationDownlink.getPosition(), downlinkDate);
// Transit state & Transit state (re)computed with gradients
final Gradient delta = downlinkDate.durationFrom(state.getDate());
final Gradient deltaMTauD = tauD.negate().add(delta);
final SpacecraftState transitState = state.shiftedBy(deltaMTauD.getValue());
final TimeStampedFieldPVCoordinates<Gradient> transitPV = pva.shiftedBy(deltaMTauD);
return new GroundReceiverCommonParametersWithDerivatives(state,
indices,
offsetToInertialDownlink,
stationDownlink,
tauD,
transitState,
transitPV);
}
/**
* Get the station position for a given frame.
* @param frame inertial frame for station position
* @return the station position in the given inertial frame
* @since 12.0
*/
public Vector3D getGroundStationPosition(final Frame frame) {
return station.getBaseFrame().getPosition(getDate(), frame);
}
/**
* Get the station coordinates for a given frame.
* @param frame inertial frame for station position
* @return the station coordinates in the given inertial frame
* @since 12.0
*/
public PVCoordinates getGroundStationCoordinates(final Frame frame) {
return station.getBaseFrame().getPVCoordinates(getDate(), frame);
}
}