OnBoardAntennaOneWayGNSSRangeModifier.java
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*
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package org.orekit.estimation.measurements.modifiers;
import java.util.Collections;
import java.util.List;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.orekit.attitudes.AttitudeProvider;
import org.orekit.estimation.measurements.EstimatedMeasurement;
import org.orekit.estimation.measurements.EstimationModifier;
import org.orekit.estimation.measurements.gnss.OneWayGNSSRange;
import org.orekit.frames.Transform;
import org.orekit.orbits.CartesianOrbit;
import org.orekit.orbits.Orbit;
import org.orekit.propagation.SpacecraftState;
import org.orekit.time.AbsoluteDate;
import org.orekit.utils.ParameterDriver;
import org.orekit.utils.TimeStampedPVCoordinates;
/** On-board antenna offset effect on one-way GNSS range measurements.
* @author Bryan Cazabonne
* @since 10.3
*/
public class OnBoardAntennaOneWayGNSSRangeModifier implements EstimationModifier<OneWayGNSSRange> {
/** Position of the Antenna Phase Center in satellite 1 frame. */
private final Vector3D antennaPhaseCenter1;
/** Position of the Antenna Phase Center in satellite 2 frame. */
private final Vector3D antennaPhaseCenter2;
/** Attitude provider of the emitting satellite. */
private final AttitudeProvider attitude;
/** Simple constructor.
* @param antennaPhaseCenter1 position of the Antenna Phase Center in satellite 1 frame
* (i.e. the satellite which receives the signal and performs the measurement)
* @param antennaPhaseCenter2 position of the Antenna Phase Center in satellite 2 frame
* (i.e. the satellite which simply emits the signal)
* @param attitude attitude provider of the emitting satellite
*/
public OnBoardAntennaOneWayGNSSRangeModifier(final Vector3D antennaPhaseCenter1,
final Vector3D antennaPhaseCenter2,
final AttitudeProvider attitude) {
this.antennaPhaseCenter1 = antennaPhaseCenter1;
this.antennaPhaseCenter2 = antennaPhaseCenter2;
this.attitude = attitude;
}
/** {@inheritDoc} */
@Override
public List<ParameterDriver> getParametersDrivers() {
return Collections.emptyList();
}
/** {@inheritDoc} */
@Override
public void modify(final EstimatedMeasurement<OneWayGNSSRange> estimated) {
// The participants are remote satellite at emission, local satellite at reception
final TimeStampedPVCoordinates[] participants = estimated.getParticipants();
final AbsoluteDate emissionDate = participants[0].getDate();
final AbsoluteDate receptionDate = participants[1].getDate();
// Transforms from spacecraft to inertial frame at reception date
final SpacecraftState refStateLocal = estimated.getStates()[0];
final SpacecraftState receptionState = refStateLocal.shiftedBy(receptionDate.durationFrom(refStateLocal.getDate()));
final Transform receptionSpacecraftToInert = receptionState.toTransform().getInverse();
// Orbit of the remote satellite
final Orbit orbitRemote = new CartesianOrbit(participants[0], refStateLocal.getFrame(), receptionState.getMu());
// Transforms from spacecraft to inertial frame at emission date
final SpacecraftState refStateRemote = new SpacecraftState(orbitRemote,
attitude.getAttitude(orbitRemote,
orbitRemote.getDate(),
orbitRemote.getFrame()));
final SpacecraftState emissionState = refStateRemote.shiftedBy(emissionDate.durationFrom(refStateRemote.getDate()));
final Transform emissionSpacecraftToInert = emissionState.toTransform().getInverse();
// Compute the geometrical value of the one-way GNSS range directly from participants positions.
// Note that this may be different from the value returned by estimated.getEstimatedValue(),
// because other modifiers may already have been taken into account
final Vector3D pSpacecraftReception = receptionSpacecraftToInert.transformPosition(Vector3D.ZERO);
final Vector3D pSpacecraftEmission = emissionSpacecraftToInert.transformPosition(Vector3D.ZERO);
final double oneWayGNSSRangeUsingSpacecraftCenter = Vector3D.distance(pSpacecraftEmission, pSpacecraftReception);
// Compute the geometrical value of the range replacing
// the spacecraft positions with antenna phase center positions
final Vector3D pAPCReception = receptionSpacecraftToInert.transformPosition(antennaPhaseCenter1);
final Vector3D pAPCEmission = emissionSpacecraftToInert.transformPosition(antennaPhaseCenter2);
final double oneWayGNSSRangeUsingAntennaPhaseCenter = Vector3D.distance(pAPCEmission, pAPCReception);
// Get the estimated value before this modifier is applied
final double[] value = estimated.getEstimatedValue();
// Modify the value
value[0] += oneWayGNSSRangeUsingAntennaPhaseCenter - oneWayGNSSRangeUsingSpacecraftCenter;
estimated.setEstimatedValue(value);
}
}