StateVector.java

/* Copyright 2002-2025 CS GROUP
 * 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.
 * 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
 * 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.files.ccsds.ndm.odm;

import java.util.Arrays;

import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitMessages;
import org.orekit.files.ccsds.section.CommentsContainer;
import org.orekit.time.AbsoluteDate;
import org.orekit.utils.TimeStampedPVCoordinates;

/** Container for state vector data.
 * <p>
 * Beware that the Orekit getters and setters all rely on SI units. The parsers
 * and writers take care of converting these SI units into CCSDS mandatory units.
 * The {@link org.orekit.utils.units.Unit Unit} class provides useful
 * {@link org.orekit.utils.units.Unit#fromSI(double) fromSi} and
 * {@link org.orekit.utils.units.Unit#toSI(double) toSI} methods in case the callers
 * already use CCSDS units instead of the API SI units. The general-purpose
 * {@link org.orekit.utils.units.Unit Unit} class (without an 's') and the
 * CCSDS-specific {@link org.orekit.files.ccsds.definitions.Units Units} class
 * (with an 's') also provide some predefined units. These predefined units and the
 * {@link org.orekit.utils.units.Unit#fromSI(double) fromSi} and
 * {@link org.orekit.utils.units.Unit#toSI(double) toSI} conversion methods are indeed
 * what the parsers and writers use for the conversions.
 * </p>
 * @author Luc Maisonobe
 * @since 11.0
 */
public class StateVector extends CommentsContainer {

    /** Epoch of state vector and optional Keplerian elements. */
    private AbsoluteDate epoch;

    /** Position vector (m). */
    private final double[] position;

    /** Velocity vector (m/s). */
    private final double[] velocity;

    /** Acceleration vector (m/s²). */
    private final double[] acceleration;

    /** Create an empty data set.
     */
    public StateVector() {
        position     = new double[3];
        velocity     = new double[3];
        acceleration = new double[3];
        Arrays.fill(position,     Double.NaN);
        Arrays.fill(velocity,     Double.NaN);
        Arrays.fill(acceleration, Double.NaN);
    }

    /** {@inheritDoc} */
    @Override
    public void validate(final double version) {
        super.validate(version);
        checkNotNull(epoch, StateVectorKey.EPOCH.name());
        if (Double.isNaN(position[0] + position[1] + position[2])) {
            throw new OrekitException(OrekitMessages.UNINITIALIZED_VALUE_FOR_KEY, "{X|Y|Z}");
        }
        if (Double.isNaN(velocity[0] + velocity[1] + velocity[2])) {
            throw new OrekitException(OrekitMessages.UNINITIALIZED_VALUE_FOR_KEY, "{X|Y|Z}_DOT");
        }
    }

    /** Get epoch of state vector, Keplerian elements and covariance matrix data.
     * @return epoch the epoch
     */
    public AbsoluteDate getEpoch() {
        return epoch;
    }

    /** Set epoch of state vector, Keplerian elements and covariance matrix data.
     * @param epoch the epoch to be set
     */
    public void setEpoch(final AbsoluteDate epoch) {
        refuseFurtherComments();
        this.epoch = epoch;
    }

    /**
     * Set position component.
     * @param index component index (counting from 0)
     * @param value position component
     */
    public void setP(final int index, final double value) {
        refuseFurtherComments();
        position[index] = value;
    }

    /**
     * Set velocity component.
     * @param index component index (counting from 0)
     * @param value velocity component
     */
    public void setV(final int index, final double value) {
        refuseFurtherComments();
        velocity[index] = value;
    }

    /**
     * Set acceleration component.
     * @param index component index (counting from 0)
     * @param value acceleration component
     */
    public void setA(final int index, final double value) {
        refuseFurtherComments();
        acceleration[index] = value;
    }

    /** Check if state contains acceleration data.
     * @return true is state contains acceleration data
     */
    public boolean hasAcceleration() {
        return !Double.isNaN(acceleration[0] + acceleration[1] + acceleration[2]);
    }

    /** Convert to {@link TimeStampedPVCoordinates}.
     * @return a new {@link TimeStampedPVCoordinates}
     */
    public TimeStampedPVCoordinates toTimeStampedPVCoordinates() {
        return new TimeStampedPVCoordinates(epoch,
                                            new Vector3D(position),
                                            new Vector3D(velocity),
                                            hasAcceleration() ? new Vector3D(acceleration) : Vector3D.ZERO);
    }

}