TwoBodiesBaryTransformProvider.java

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 * CS licenses this file to You under the Apache License, Version 2.0
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package org.orekit.frames;

import org.hipparchus.CalculusFieldElement;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.orekit.bodies.CelestialBody;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.utils.FieldPVCoordinates;
import org.orekit.utils.PVCoordinates;

/** Transform provider for the inertial Barycentered frame.
 * @author Vincent Mouraux
 * @since 10.2
 */
class TwoBodiesBaryTransformProvider implements TransformProvider {

    /** Frame for results. Always defined as primaryBody's inertially oriented frame.*/
    private final Frame frame;

    /** Celestial body with bigger mass, m1. */
    private final CelestialBody primaryBody;

    /** Celestial body with smaller mass, m2. */
    private final CelestialBody secondaryBody;


    /** Simple constructor.
     * @param primaryBody Primary body.
     * @param secondaryBody Secondary body.
     */
    TwoBodiesBaryTransformProvider(final CelestialBody primaryBody, final CelestialBody secondaryBody) {
        this.primaryBody = primaryBody;
        this.secondaryBody = secondaryBody;
        this.frame = primaryBody.getInertiallyOrientedFrame();
    }

    /** {@inheritDoc} */
    @Override
    public Transform getTransform(final AbsoluteDate date) {
        final PVCoordinates pv21 = secondaryBody.getPVCoordinates(date, frame);
        final double massRatio = secondaryBody.getGM() / (primaryBody.getGM() + secondaryBody.getGM());
        final Vector3D translation = pv21.getPosition().scalarMultiply(massRatio).negate();
        return new Transform(date, translation);
    }

    /** {@inheritDoc} */
    @Override
    public <T extends CalculusFieldElement<T>> FieldTransform<T> getTransform(final FieldAbsoluteDate<T> date) {
        final FieldPVCoordinates<T> pv21        = secondaryBody.getPVCoordinates(date, frame);
        final double massRatio = secondaryBody.getGM() / (primaryBody.getGM() + secondaryBody.getGM());
        final FieldVector3D<T> translation = pv21.getPosition().scalarMultiply(massRatio).negate();
        return new FieldTransform<>(date, translation);
    }
}