BistaticRangeIonosphericDelayModifier.java

/* Copyright 2002-2025 Mark Rutten
 * Licensed to CS GROUP (CS) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * Mark Rutten 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 org.orekit.attitudes.FrameAlignedProvider;
import org.orekit.estimation.measurements.BistaticRange;
import org.orekit.estimation.measurements.EstimatedMeasurement;
import org.orekit.estimation.measurements.EstimatedMeasurementBase;
import org.orekit.estimation.measurements.EstimationModifier;
import org.orekit.estimation.measurements.GroundStation;
import org.orekit.models.earth.ionosphere.IonosphericModel;
import org.orekit.propagation.SpacecraftState;

/**
 * Class modifying theoretical bistatic range measurement with ionospheric delay.
 * The effect of ionospheric correction on the range is directly computed
 * through the computation of the ionospheric delay.
 * <p>
 * The ionospheric delay depends on the frequency of the signal (GNSS, VLBI, ...).
 * For optical measurements (e.g. SLR), the ray is not affected by ionosphere charged particles.
 * <p>
 * Since 10.0, state derivatives and ionospheric parameters derivates are computed
 * using automatic differentiation.
 * </p>
 *
 * @author Maxime Journot
 * @author Joris Olympio
 * @author Mark Rutten
 * @since 11.2
 */
public class BistaticRangeIonosphericDelayModifier extends BaseRangeIonosphericDelayModifier implements EstimationModifier<BistaticRange> {

    /**
     * Constructor.
     *
     * @param model Ionospheric delay model appropriate for the current range measurement method.
     * @param freq  frequency of the signal in Hz
     */
    public BistaticRangeIonosphericDelayModifier(final IonosphericModel model,
                                                 final double freq) {
        super(model, freq);
    }

    /** {@inheritDoc} */
    @Override
    public void modifyWithoutDerivatives(final EstimatedMeasurementBase<BistaticRange> estimated) {

        final BistaticRange measurement = estimated.getObservedMeasurement();
        final GroundStation emitter     = measurement.getEmitterStation();
        final GroundStation receiver    = measurement.getReceiverStation();

        BistaticModifierUtil.modify(estimated, emitter, receiver,
                                    this::rangeErrorIonosphericModel, this);

    }

    /** {@inheritDoc} */
    @Override
    public void modify(final EstimatedMeasurement<BistaticRange> estimated) {

        final BistaticRange measurement = estimated.getObservedMeasurement();
        final GroundStation emitter     = measurement.getEmitterStation();
        final GroundStation receiver    = measurement.getReceiverStation();
        final SpacecraftState state     = estimated.getStates()[0];

        BistaticModifierUtil.modify(estimated, getIonoModel(),
                                    new ModifierGradientConverter(state, 6, new FrameAlignedProvider(state.getFrame())),
                                    emitter, receiver,
                                    this::rangeErrorIonosphericModel,
                                    this::rangeErrorIonosphericModel,
                                    this);

    }

}