OnBoardAntennaTurnAroundRangeModifier.java
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* CS licenses this file to You under the Apache License, Version 2.0
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*
* http://www.apache.org/licenses/LICENSE-2.0
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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.estimation.measurements.EstimatedMeasurement;
import org.orekit.estimation.measurements.EstimationModifier;
import org.orekit.estimation.measurements.TurnAroundRange;
import org.orekit.frames.Transform;
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 turn around range measurements.
* @author Luc Maisonobe
* @since 9.0
*/
public class OnBoardAntennaTurnAroundRangeModifier implements EstimationModifier<TurnAroundRange> {
/** Position of the Antenna Phase Center in satellite frame. */
private final Vector3D antennaPhaseCenter;
/** Simple constructor.
* @param antennaPhaseCenter position of the Antenna Phase Center in satellite frame
*/
public OnBoardAntennaTurnAroundRangeModifier(final Vector3D antennaPhaseCenter) {
this.antennaPhaseCenter = antennaPhaseCenter;
}
/** {@inheritDoc} */
@Override
public List<ParameterDriver> getParametersDrivers() {
return Collections.emptyList();
}
/** {@inheritDoc} */
@Override
public void modify(final EstimatedMeasurement<TurnAroundRange> estimated) {
// the participants are primary station at emission, spacecraft during leg 1,
// secondary station at rebound, spacecraft during leg 2, primary station at reception
final TimeStampedPVCoordinates[] participants = estimated.getParticipants();
final Vector3D pPrimaryEmission = participants[0].getPosition();
final AbsoluteDate transitDateLeg1 = participants[1].getDate();
final Vector3D pSecondaryRebound = participants[2].getPosition();
final AbsoluteDate transitDateLeg2 = participants[3].getDate();
final Vector3D pPrimaryReception = participants[4].getPosition();
// transforms from spacecraft to inertial frame at transit dates
final SpacecraftState refState = estimated.getStates()[0];
final SpacecraftState transitStateLeg1 = refState.shiftedBy(transitDateLeg1.durationFrom(refState.getDate()));
final Transform spacecraftToInertLeg1 = transitStateLeg1.toTransform().getInverse();
final SpacecraftState transitStateLeg2 = refState.shiftedBy(transitDateLeg2.durationFrom(refState.getDate()));
final Transform spacecraftToInertLeg2 = transitStateLeg2.toTransform().getInverse();
// compute the geometrical value of the turn-around 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 pSpacecraftLeg1 = spacecraftToInertLeg1.transformPosition(Vector3D.ZERO);
final Vector3D pSpacecraftLeg2 = spacecraftToInertLeg2.transformPosition(Vector3D.ZERO);
final double turnAroundRangeUsingSpacecraftCenter =
0.5 * (Vector3D.distance(pPrimaryEmission, pSpacecraftLeg1) +
Vector3D.distance(pSpacecraftLeg1, pSecondaryRebound) +
Vector3D.distance(pSecondaryRebound, pSpacecraftLeg2) +
Vector3D.distance(pSpacecraftLeg2, pPrimaryReception));
// compute the geometrical value of the range replacing
// the spacecraft positions with antenna phase center positions
final Vector3D pAPCLeg1 = spacecraftToInertLeg1.transformPosition(antennaPhaseCenter);
final Vector3D pAPCLeg2 = spacecraftToInertLeg2.transformPosition(antennaPhaseCenter);
final double turnAroundRangeUsingAntennaPhaseCenter =
0.5 * (Vector3D.distance(pPrimaryEmission, pAPCLeg1) +
Vector3D.distance(pAPCLeg1, pSecondaryRebound) +
Vector3D.distance(pSecondaryRebound, pAPCLeg2) +
Vector3D.distance(pAPCLeg2, pPrimaryReception));
// get the estimated value before this modifier is applied
final double[] value = estimated.getEstimatedValue();
// modify the value
value[0] += turnAroundRangeUsingAntennaPhaseCenter - turnAroundRangeUsingSpacecraftCenter;
estimated.setEstimatedValue(value);
}
}