AngularRadioRefractionModifier.java
- /* Copyright 2002-2017 CS Systèmes d'Information
- * Licensed to CS Systèmes d'Information (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.modifiers;
- import java.util.Collections;
- import java.util.List;
- import org.hipparchus.geometry.euclidean.threed.Vector3D;
- import org.orekit.errors.OrekitException;
- 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
- * @throws OrekitException if frames transformations cannot be computed
- */
- private double angularErrorRadioRefractionModel(final GroundStation station,
- final SpacecraftState state)
- throws OrekitException {
- 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)
- throws OrekitException {
- 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]);
- }
- }