ShapiroPhaseModifier.java

/* Copyright 2002-2024 CS GROUP
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 * 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
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package org.orekit.estimation.measurements.modifiers;

import java.util.Collections;
import java.util.List;

import org.orekit.estimation.measurements.EstimatedMeasurementBase;
import org.orekit.estimation.measurements.EstimationModifier;
import org.orekit.estimation.measurements.gnss.Phase;
import org.orekit.utils.ParameterDriver;
import org.orekit.utils.TimeStampedPVCoordinates;

/** Class modifying theoretical phase measurement with Shapiro time delay.
 * <p>
 * Shapiro time delay is a relativistic effect due to gravity.
 * </p>
 *
 * @author Bryan Cazabonne
 * @author Luc Maisonobe
 * @since 10.2
 */
public class ShapiroPhaseModifier extends AbstractShapiroBaseModifier implements EstimationModifier<Phase> {

    /** Simple constructor.
     * @param gm gravitational constant for main body in signal path vicinity.
     */
    public ShapiroPhaseModifier(final double gm) {
        super(gm);
    }

    /** {@inheritDoc} */
    @Override
    public List<ParameterDriver> getParametersDrivers() {
        return Collections.emptyList();
    }

    /** {@inheritDoc} */
    @Override
    public void modifyWithoutDerivatives(final EstimatedMeasurementBase<Phase> estimated) {
        // wavelength
        final double wavelength = estimated.getObservedMeasurement().getWavelength();

        // compute correction
        final TimeStampedPVCoordinates[] pv = estimated.getParticipants();
        final double correction = shapiroCorrection(pv[0], pv[1]) / wavelength;

        // update estimated value taking into account the Shapiro time delay.
        final double[] newValue = estimated.getEstimatedValue().clone();
        newValue[0] = newValue[0] + correction;
        estimated.modifyEstimatedValue(this, newValue);
    }

}