GalileoPropagator.java

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package org.orekit.propagation.analytical.gnss;

import org.orekit.annotation.DefaultDataContext;
import org.orekit.attitudes.AttitudeProvider;
import org.orekit.data.DataContext;
import org.orekit.frames.Frame;
import org.orekit.frames.Frames;
import org.orekit.propagation.Propagator;
import org.orekit.utils.IERSConventions;

/**
 * This class aims at propagating a Galileo orbit from {@link GalileoOrbitalElements}.
 *
 * @see <a href="https://www.gsc-europa.eu/system/files/galileo_documents/Galileo-OS-SIS-ICD.pdf">Galileo Interface Control Document</a>
 *
 * @author Bryan Cazabonne
 *
 */
public class GalileoPropagator extends AbstractGNSSPropagator {

    // Constants
    /** Value of the earth's rotation rate in rad/s. */
    private static final double GALILEO_AV = 7.2921151467e-5;

    /** Duration of the Galileo cycle in seconds. */
    private static final double GALILEO_CYCLE_DURATION = GalileoOrbitalElements.GALILEO_WEEK_IN_SECONDS *
                                                         GalileoOrbitalElements.GALILEO_WEEK_NB;

    // Fields
    /** The Galileo orbital elements used. */
    private final GalileoOrbitalElements galileoOrbit;

    /**
     * This nested class aims at building a GalileoPropagator.
     * <p>It implements the classical builder pattern.</p>
     *
     */
    public static class Builder {

        // Required parameter
        /** The Galileo orbital elements. */
        private final GalileoOrbitalElements orbit;

        // Optional parameters
        /** The attitude provider. */
        private AttitudeProvider attitudeProvider;
        /** The mass. */
        private double mass = DEFAULT_MASS;
        /** The ECI frame. */
        private Frame eci  = null;
        /** The ECEF frame. */
        private Frame ecef = null;

        /** Initializes the builder.
         * <p>The Galileo orbital elements is the only requested parameter to build a GalileoPropagator.</p>
         * <p>The attitude provider is set by default to the
         *  {@link org.orekit.propagation.Propagator#DEFAULT_LAW DEFAULT_LAW} in the
         *  default data context.<br>
         * The mass is set by default to the
         *  {@link org.orekit.propagation.Propagator#DEFAULT_MASS DEFAULT_MASS}.<br>
         * The ECI frame is set by default to the
         *  {@link org.orekit.frames.Predefined#EME2000 EME2000 frame} in the default data
         *  context.<br>
         * The ECEF frame is set by default to the
         *  {@link org.orekit.frames.Predefined#ITRF_CIO_CONV_2010_SIMPLE_EOP
         *  CIO/2010-based ITRF simple EOP} in the default data context.
         * </p>
         *
         * <p>This constructor uses the {@link DataContext#getDefault() default data context}.
         * Another data context can be set using
         * {@code Builder(final GalileoOrbitalElements gpsOrbElt, final Frames frames)}</p>
         *
         * @param galileoOrbElt the Galileo orbital elements to be used by the Galileo propagator.
         * @see #attitudeProvider(AttitudeProvider provider)
         * @see #mass(double mass)
         * @see #eci(Frame inertial)
         * @see #ecef(Frame bodyFixed)
         */
        @DefaultDataContext
        public Builder(final GalileoOrbitalElements galileoOrbElt) {
            this(galileoOrbElt, DataContext.getDefault().getFrames());
        }

        /** Initializes the builder.
         * <p>The Galileo orbital elements is the only requested parameter to build a GalileoPropagator.</p>
         * <p>The attitude provider is set by default to the
         *  {@link org.orekit.propagation.Propagator#getDefaultLaw(Frames) DEFAULT_LAW}.<br>
         * The mass is set by default to the
         *  {@link org.orekit.propagation.Propagator#DEFAULT_MASS DEFAULT_MASS}.<br>
         * The ECI frame is set by default to the
         *  {@link org.orekit.frames.Predefined#EME2000 EME2000 frame}.<br>
         * The ECEF frame is set by default to the
         *  {@link org.orekit.frames.Predefined#ITRF_CIO_CONV_2010_SIMPLE_EOP CIO/2010-based ITRF simple EOP}.
         * </p>
         *
         * @param galileoOrbElt the Galileo orbital elements to be used by the Galileo propagator.
         * @param frames to use building the propagator.
         * @see #attitudeProvider(AttitudeProvider provider)
         * @see #mass(double mass)
         * @see #eci(Frame inertial)
         * @see #ecef(Frame bodyFixed)
         * @since 10.1
         */
        public Builder(final GalileoOrbitalElements galileoOrbElt, final Frames frames) {
            this.orbit = galileoOrbElt;
            this.eci   = frames.getEME2000();
            this.ecef  = frames.getITRF(IERSConventions.IERS_2010, true);
            attitudeProvider = Propagator.getDefaultLaw(frames);
        }

        /** Sets the attitude provider.
         *
         * @param userProvider the attitude provider
         * @return the updated builder
         */
        public Builder attitudeProvider(final AttitudeProvider userProvider) {
            this.attitudeProvider = userProvider;
            return this;
        }

        /** Sets the mass.
         *
         * @param userMass the mass (in kg)
         * @return the updated builder
         */
        public Builder mass(final double userMass) {
            this.mass = userMass;
            return this;
        }

        /** Sets the Earth Centered Inertial frame used for propagation.
         *
         * @param inertial the ECI frame
         * @return the updated builder
         */
        public Builder eci(final Frame inertial) {
            this.eci = inertial;
            return this;
        }

        /** Sets the Earth Centered Earth Fixed frame.
         *
         * @param bodyFixed the ECEF frame
         * @return the updated builder
         */
        public Builder ecef(final Frame bodyFixed) {
            this.ecef = bodyFixed;
            return this;
        }

        /** Finalizes the build.
         *
         * @return the built GalileoPropagator
         */
        public GalileoPropagator build() {
            return new GalileoPropagator(this);
        }
    }

    /**
     * Private constructor.
     *
     * @param builder the builder
     */
    private GalileoPropagator(final Builder builder) {
        super(builder.orbit, builder.attitudeProvider,
              builder.eci, builder.ecef, builder.mass,
              GALILEO_AV, GALILEO_CYCLE_DURATION, GalileoOrbitalElements.GALILEO_MU);
        // Stores the Galileo orbital elements
        this.galileoOrbit = builder.orbit;
    }

    /**
     * Get the underlying Galileo orbital elements.
     *
     * @return the underlying Galileo orbital elements
     */
    public GalileoOrbitalElements getGalileoOrbitalElements() {
        return galileoOrbit;
    }

}