TimeStampedAngularCoordinates.java

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 * contributor license agreements.  See the NOTICE file distributed with
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 * CS licenses this file to You under the Apache License, Version 2.0
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package org.orekit.utils;

import org.hipparchus.analysis.differentiation.Derivative;
import org.hipparchus.geometry.euclidean.threed.FieldRotation;
import org.hipparchus.geometry.euclidean.threed.Rotation;
import org.hipparchus.geometry.euclidean.threed.RotationConvention;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.TimeStamped;

/** {@link TimeStamped time-stamped} version of {@link AngularCoordinates}.
 * <p>Instances of this class are guaranteed to be immutable.</p>
 * @author Luc Maisonobe
 * @since 7.0
 */
public class TimeStampedAngularCoordinates extends AngularCoordinates implements TimeStamped {

    /** Serializable UID. */
    private static final long serialVersionUID = 20140723L;

    /** The date. */
    private final AbsoluteDate date;

    /** Builds a rotation/rotation rate pair.
     * @param date coordinates date
     * @param rotation rotation
     * @param rotationRate rotation rate Ω (rad/s)
     * @param rotationAcceleration rotation acceleration dΩ/dt (rad²/s²)
     */
    public TimeStampedAngularCoordinates(final AbsoluteDate date,
                                         final Rotation rotation,
                                         final Vector3D rotationRate,
                                         final Vector3D rotationAcceleration) {
        super(rotation, rotationRate, rotationAcceleration);
        this.date = date;
    }

    /** Build the rotation that transforms a pair of pv coordinates into another pair.

     * <p><em>WARNING</em>! This method requires much more stringent assumptions on
     * its parameters than the similar {@link Rotation#Rotation(Vector3D, Vector3D,
     * Vector3D, Vector3D) constructor} from the {@link Rotation Rotation} class.
     * As far as the Rotation constructor is concerned, the {@code v₂} vector from
     * the second pair can be slightly misaligned. The Rotation constructor will
     * compensate for this misalignment and create a rotation that ensure {@code
     * v₁ = r(u₁)} and {@code v₂ ∈ plane (r(u₁), r(u₂))}. <em>THIS IS NOT
     * TRUE ANYMORE IN THIS CLASS</em>! As derivatives are involved and must be
     * preserved, this constructor works <em>only</em> if the two pairs are fully
     * consistent, i.e. if a rotation exists that fulfill all the requirements: {@code
     * v₁ = r(u₁)}, {@code v₂ = r(u₂)}, {@code dv₁/dt = dr(u₁)/dt}, {@code dv₂/dt
     * = dr(u₂)/dt}, {@code d²v₁/dt² = d²r(u₁)/dt²}, {@code d²v₂/dt² = d²r(u₂)/dt²}.</p>

     * @param date coordinates date
     * @param u1 first vector of the origin pair
     * @param u2 second vector of the origin pair
     * @param v1 desired image of u1 by the rotation
     * @param v2 desired image of u2 by the rotation
     * @param tolerance relative tolerance factor used to check singularities
     */
    public TimeStampedAngularCoordinates(final AbsoluteDate date,
                                         final PVCoordinates u1, final PVCoordinates u2,
                                         final PVCoordinates v1, final PVCoordinates v2,
                                         final double tolerance) {
        super(u1, u2, v1, v2, tolerance);
        this.date = date;
    }

    /** Build one of the rotations that transform one pv coordinates into another one.

     * <p>Except for a possible scale factor, if the instance were
     * applied to the vector u it will produce the vector v. There is an
     * infinite number of such rotations, this constructor choose the
     * one with the smallest associated angle (i.e. the one whose axis
     * is orthogonal to the (u, v) plane). If u and v are collinear, an
     * arbitrary rotation axis is chosen.</p>

     * @param date coordinates date
     * @param u origin vector
     * @param v desired image of u by the rotation
     */
    public TimeStampedAngularCoordinates(final AbsoluteDate date,
                                         final PVCoordinates u, final PVCoordinates v) {
        super(u, v);
        this.date = date;
    }

    /** Builds a TimeStampedAngularCoordinates from  a {@link FieldRotation}&lt;{@link Derivative}&gt;.
     * <p>
     * The rotation components must have time as their only derivation parameter and
     * have consistent derivation orders.
     * </p>
     * @param date coordinates date
     * @param r rotation with time-derivatives embedded within the coordinates
     * @param <U> type of the derivative
     */
    public <U extends Derivative<U>>TimeStampedAngularCoordinates(final AbsoluteDate date,
                                                                  final FieldRotation<U> r) {
        super(r);
        this.date = date;
    }

    /** {@inheritDoc} */
    public AbsoluteDate getDate() {
        return date;
    }

    /** Revert a rotation/rotation rate pair.
     * Build a pair which reverse the effect of another pair.
     * @return a new pair whose effect is the reverse of the effect
     * of the instance
     */
    public TimeStampedAngularCoordinates revert() {
        return new TimeStampedAngularCoordinates(date,
                                                 getRotation().revert(),
                                                 getRotation().applyInverseTo(getRotationRate().negate()),
                                                 getRotation().applyInverseTo(getRotationAcceleration().negate()));
    }

    /** Get a time-shifted state.
     * <p>
     * The state can be slightly shifted to close dates. This shift is based on
     * a simple linear model. It is <em>not</em> intended as a replacement for
     * proper attitude propagation but should be sufficient for either small
     * time shifts or coarse accuracy.
     * </p>
     * @param dt time shift in seconds
     * @return a new state, shifted with respect to the instance (which is immutable)
     */
    public TimeStampedAngularCoordinates shiftedBy(final double dt) {
        final AngularCoordinates sac = super.shiftedBy(dt);
        return new TimeStampedAngularCoordinates(date.shiftedBy(dt),
                                                 sac.getRotation(), sac.getRotationRate(), sac.getRotationAcceleration());

    }

    /** Add an offset from the instance.
     * <p>
     * We consider here that the offset rotation is applied first and the
     * instance is applied afterward. Note that angular coordinates do <em>not</em>
     * commute under this operation, i.e. {@code a.addOffset(b)} and {@code
     * b.addOffset(a)} lead to <em>different</em> results in most cases.
     * </p>
     * <p>
     * The two methods {@link #addOffset(AngularCoordinates) addOffset} and
     * {@link #subtractOffset(AngularCoordinates) subtractOffset} are designed
     * so that round trip applications are possible. This means that both {@code
     * ac1.subtractOffset(ac2).addOffset(ac2)} and {@code
     * ac1.addOffset(ac2).subtractOffset(ac2)} return angular coordinates equal to ac1.
     * </p>
     * @param offset offset to subtract
     * @return new instance, with offset subtracted
     * @see #subtractOffset(AngularCoordinates)
     */
    @Override
    public TimeStampedAngularCoordinates addOffset(final AngularCoordinates offset) {
        final Vector3D rOmega    = getRotation().applyTo(offset.getRotationRate());
        final Vector3D rOmegaDot = getRotation().applyTo(offset.getRotationAcceleration());
        return new TimeStampedAngularCoordinates(date,
                                                 getRotation().compose(offset.getRotation(), RotationConvention.VECTOR_OPERATOR),
                                                 getRotationRate().add(rOmega),
                                                 new Vector3D( 1.0, getRotationAcceleration(),
                                                               1.0, rOmegaDot,
                                                              -1.0, Vector3D.crossProduct(getRotationRate(), rOmega)));
    }

    /** Subtract an offset from the instance.
     * <p>
     * We consider here that the offset rotation is applied first and the
     * instance is applied afterward. Note that angular coordinates do <em>not</em>
     * commute under this operation, i.e. {@code a.subtractOffset(b)} and {@code
     * b.subtractOffset(a)} lead to <em>different</em> results in most cases.
     * </p>
     * <p>
     * The two methods {@link #addOffset(AngularCoordinates) addOffset} and
     * {@link #subtractOffset(AngularCoordinates) subtractOffset} are designed
     * so that round trip applications are possible. This means that both {@code
     * ac1.subtractOffset(ac2).addOffset(ac2)} and {@code
     * ac1.addOffset(ac2).subtractOffset(ac2)} return angular coordinates equal to ac1.
     * </p>
     * @param offset offset to subtract
     * @return new instance, with offset subtracted
     * @see #addOffset(AngularCoordinates)
     */
    @Override
    public TimeStampedAngularCoordinates subtractOffset(final AngularCoordinates offset) {
        return addOffset(offset.revert());
    }

}