AbstractInterSatellitesMeasurement.java
/* Copyright 2002-2024 Luc Maisonobe
* 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.gnss;
import java.util.Arrays;
import org.hipparchus.analysis.differentiation.Gradient;
import org.orekit.estimation.measurements.ObservableSatellite;
import org.orekit.estimation.measurements.ObservedMeasurement;
import org.orekit.estimation.measurements.QuadraticClockModel;
import org.orekit.propagation.SpacecraftState;
import org.orekit.time.AbsoluteDate;
import org.orekit.utils.FieldPVCoordinatesProvider;
import org.orekit.utils.PVCoordinatesProvider;
import org.orekit.utils.ShiftingPVCoordinatesProvider;
import org.orekit.utils.TimeStampedFieldPVCoordinates;
/** Base class for measurement between two satellites that are both estimated.
* <p>
* The measurement is considered to be a signal emitted from
* a remote satellite and received by a local satellite.
* Its value is the number of cycles between emission and reception.
* The motion of both spacecraft during the signal flight time
* are taken into account. The date of the measurement corresponds to the
* reception on ground of the emitted signal.
* </p>
* @param <T> type of the measurement
* @author Luc Maisonobe
* @since 12.1
*/
public abstract class AbstractInterSatellitesMeasurement<T extends ObservedMeasurement<T>> extends AbstractOnBoardMeasurement<T> {
/** Constructor.
* @param date date of the measurement
* @param observed observed value
* @param sigma theoretical standard deviation
* @param baseWeight base weight
* @param local satellite which receives the signal and performs the measurement
* @param remote remote satellite which simply emits the signal
*/
public AbstractInterSatellitesMeasurement(final AbsoluteDate date, final double observed,
final double sigma, final double baseWeight,
final ObservableSatellite local,
final ObservableSatellite remote) {
// Call to super constructor
super(date, observed, sigma, baseWeight, Arrays.asList(local, remote));
}
/** {@inheritDoc} */
@Override
protected PVCoordinatesProvider getRemotePV(final SpacecraftState[] states) {
return new ShiftingPVCoordinatesProvider(states[1].getPVCoordinates(), states[1].getFrame());
}
/** {@inheritDoc} */
@Override
protected QuadraticClockModel getRemoteClock() {
return getSatellites().get(1).getQuadraticClockModel();
}
/** {@inheritDoc} */
@Override
protected FieldPVCoordinatesProvider<Gradient> getRemotePV(final SpacecraftState[] states,
final int freeParameters) {
// convert the SpacecraftState to a FieldPVCoordinatesProvider<Gradient>
return (date, frame) -> {
// set up the derivatives with respect to remote state at its date
final TimeStampedFieldPVCoordinates<Gradient> pv0 = getCoordinates(states[1], 6, freeParameters);
// shift to desired date
final TimeStampedFieldPVCoordinates<Gradient> shifted = pv0.shiftedBy(date.durationFrom(states[1].getDate()));
// transform to desired frame
return states[1].getFrame().getTransformTo(frame, states[1].getDate()).transformPVCoordinates(shifted);
};
}
}