Atmosphere.java

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package org.orekit.models.earth.atmosphere;

import org.hipparchus.CalculusFieldElement;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.orekit.frames.FieldKinematicTransform;
import org.orekit.frames.Frame;
import org.orekit.frames.KinematicTransform;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.FieldAbsoluteDate;
import org.orekit.utils.FieldPVCoordinates;
import org.orekit.utils.PVCoordinates;


/** Interface for atmospheric models.
 * @author Luc Maisonobe
 */
public interface Atmosphere {

    /** Get the frame of the central body.
     * @return frame of the central body.
     * @since 6.0
     */
    Frame getFrame();

    /** Get the local density.
     * @param date current date
     * @param position current position in frame
     * @param frame the frame in which is defined the position
     * @return local density (kg/m³)
     */
    double getDensity(AbsoluteDate date, Vector3D position, Frame frame);

    /** Get the local density.
     * @param date current date
     * @param position current position in frame
     * @param frame the frame in which is defined the position
     * @param <T> instance of CalculusFieldElement
     * @return local density (kg/m³)
     */
    <T extends CalculusFieldElement<T>> T getDensity(FieldAbsoluteDate<T> date, FieldVector3D<T> position, Frame frame);

    /** Get the inertial velocity of atmosphere molecules.
     * <p>By default, atmosphere is supposed to have a null
     * velocity in the central body frame.</p>
     *
     * @param date current date
     * @param position current position in frame
     * @param frame the frame in which is defined the position
     * @return velocity (m/s) (defined in the same frame as the position)
     */
    default Vector3D getVelocity(AbsoluteDate date, Vector3D position, Frame frame) {
        final KinematicTransform bodyToFrame = getFrame().getKinematicTransformTo(frame, date);
        final Vector3D      posInBody   = bodyToFrame.getStaticInverse().transformPosition(position);
        final PVCoordinates pvBody      = new PVCoordinates(posInBody, Vector3D.ZERO);
        final PVCoordinates pvFrame     = bodyToFrame.transformOnlyPV(pvBody);
        return pvFrame.getVelocity();
    }

    /** Get the inertial velocity of atmosphere molecules.
     * @param date current date
     * @param position current position in frame
     * @param frame the frame in which is defined the position
     * @param <T> instance of CalculusFieldElement
     * @return velocity (m/s) (defined in the same frame as the position)
     */
    default <T extends CalculusFieldElement<T>> FieldVector3D<T> getVelocity(FieldAbsoluteDate<T> date,
                                                                             FieldVector3D<T> position,
                                                                             Frame frame) {
        final FieldKinematicTransform<T> bodyToFrame = getFrame().getKinematicTransformTo(frame, date);
        final FieldVector3D<T>      posInBody   = bodyToFrame.getStaticInverse().transformPosition(position);
        final FieldPVCoordinates<T> pvBody      = new FieldPVCoordinates<>(posInBody,
                FieldVector3D.getZero(date.getField()));
        final FieldPVCoordinates<T> pvFrame     = bodyToFrame.transformOnlyPV(pvBody);
        return pvFrame.getVelocity();
    }

}