AngularRadioRefractionModifier.java
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* CS licenses this file to You under the Apache License, Version 2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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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.AngularAzEl;
import org.orekit.estimation.measurements.EstimatedMeasurement;
import org.orekit.estimation.measurements.EstimationModifier;
import org.orekit.estimation.measurements.GroundStation;
import org.orekit.models.AtmosphericRefractionModel;
import org.orekit.propagation.SpacecraftState;
import org.orekit.utils.ParameterDriver;
/** Class modifying theoretical angular measurement with ionospheric radio refractive index.
* A radio ray passing through the lower (non-ionized) layer of the atmosphere undergoes bending
* caused by the gradient of the relative index. Since the refractive index varies mainly with
* altitude, only the vertical gradient of the refractive index is considered here.
* The effect of ionospheric correction on the angular measurement is computed directly
* through the computation of the apparent elevation angle.
* Recommendation ITU-R P.453-11 (07/2015) and Recommendation ITU-R P.834-7 (10/2015)
*
*
* @author Thierry Ceolin
* @since 8.0
*/
public class AngularRadioRefractionModifier implements EstimationModifier<AngularAzEl> {
/** Tropospheric refraction model. */
private final AtmosphericRefractionModel atmosModel;
/** Constructor.
*
* @param model tropospheric refraction model appropriate for the current angular measurement method.
*/
public AngularRadioRefractionModifier(final AtmosphericRefractionModel model) {
atmosModel = model;
}
/** Compute the measurement error due to troposphere refraction.
* @param station station
* @param state spacecraft state
* @return the measurement error due to ionosphere
*/
private double angularErrorRadioRefractionModel(final GroundStation station,
final SpacecraftState state) {
final Vector3D position = state.getPVCoordinates().getPosition();
// elevation in radians
final double elevation = station.getBaseFrame().getElevation(position,
state.getFrame(),
state.getDate());
// angle correction (rad)
return atmosModel.getRefraction(elevation);
}
/** {@inheritDoc} */
@Override
public List<ParameterDriver> getParametersDrivers() {
return Collections.emptyList();
}
@Override
public void modify(final EstimatedMeasurement<AngularAzEl> estimated) {
final AngularAzEl measure = estimated.getObservedMeasurement();
final GroundStation station = measure.getStation();
final SpacecraftState state = estimated.getStates()[0];
final double correction = angularErrorRadioRefractionModel(station, state);
// update estimated value taking into account the tropospheric elevation corection.
// The tropospheric elevation correction is directly added to the elevation.
final double[] oldValue = estimated.getEstimatedValue();
final double[] newValue = oldValue.clone();
// consider only effect on elevation
newValue[1] = newValue[1] + correction;
estimated.setEstimatedValue(newValue[0], newValue[1]);
}
}