SolidTides.java

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 * CS licenses this file to You under the Apache License, Version 2.0
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 *
 *   http://www.apache.org/licenses/LICENSE-2.0
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package org.orekit.forces.gravity;

import org.orekit.bodies.CelestialBody;
import org.orekit.forces.ForceModel;
import org.orekit.forces.ForceModelModifier;
import org.orekit.forces.gravity.potential.CachedNormalizedSphericalHarmonicsProvider;
import org.orekit.forces.gravity.potential.NormalizedSphericalHarmonicsProvider;
import org.orekit.forces.gravity.potential.TideSystem;
import org.orekit.frames.Frame;
import org.orekit.time.TimeScales;
import org.orekit.time.UT1Scale;
import org.orekit.utils.Constants;
import org.orekit.utils.IERSConventions;
import org.orekit.utils.OrekitConfiguration;

/** Solid tides force model.
 * @since 6.1
 * @author Luc Maisonobe
 */
public class SolidTides implements ForceModelModifier {

    /**
     * Default step for tides field sampling (seconds).
     */
    public static final double DEFAULT_STEP = 600.0;

    /**
     * Default number of points tides field sampling.
     */
    public static final int DEFAULT_POINTS = 12;

    /**
     * Underlying attraction model.
     */
    private final ForceModel attractionModel;

    /**
     * Simple constructor.
     * <p>
     * This constructor uses pole tides, the default {@link #DEFAULT_STEP step} and default
     * {@link #DEFAULT_POINTS number of points} for the tides field interpolation.
     * </p>
     *
     * @param centralBodyFrame  rotating body frame
     * @param ae                central body reference radius
     * @param mu                central body attraction coefficient
     * @param centralTideSystem tide system used in the central attraction model
     * @param conventions       IERS conventions used for loading Love numbers
     * @param ut1               UT1 time scale
     * @param bodies            tide generating bodies (typically Sun and Moon)
     * @see #DEFAULT_STEP
     * @see #DEFAULT_POINTS
     * @see #SolidTides(Frame, double, double, TideSystem, boolean, double, int, IERSConventions, UT1Scale, CelestialBody...)
     */
    public SolidTides(final Frame centralBodyFrame, final double ae, final double mu,
                      final TideSystem centralTideSystem,
                      final IERSConventions conventions, final UT1Scale ut1,
                      final CelestialBody... bodies) {
        this(centralBodyFrame, ae, mu, centralTideSystem, true,
                DEFAULT_STEP, DEFAULT_POINTS, conventions, ut1, bodies);
    }

    /**
     * Simple constructor.
     *
     * @param centralBodyFrame  rotating body frame
     * @param ae                central body reference radius
     * @param mu                central body attraction coefficient
     * @param centralTideSystem tide system used in the central attraction model
     * @param poleTide          if true, pole tide is computed
     * @param step              time step between sample points for interpolation
     * @param nbPoints          number of points to use for interpolation, if less than 2
     *                          then no interpolation is performed (thus greatly increasing computation cost)
     * @param conventions       IERS conventions used for loading Love numbers
     * @param ut1               UT1 time scale
     * @param bodies            tide generating bodies (typically Sun and Moon)
     */
    public SolidTides(final Frame centralBodyFrame, final double ae, final double mu,
                      final TideSystem centralTideSystem, final boolean poleTide,
                      final double step, final int nbPoints,
                      final IERSConventions conventions, final UT1Scale ut1,
                      final CelestialBody... bodies) {
        final TimeScales timeScales = ut1.getEOPHistory().getTimeScales();
        final SolidTidesField raw =
                new SolidTidesField(conventions.getLoveNumbers(),
                        conventions.getTideFrequencyDependenceFunction(ut1, timeScales),
                        conventions.getPermanentTide(),
                        poleTide ? conventions.getSolidPoleTide(ut1.getEOPHistory()) : null,
                        centralBodyFrame, ae, mu, centralTideSystem, bodies);
        final NormalizedSphericalHarmonicsProvider provider;
        if (nbPoints < 2) {
            provider = raw;
        } else {
            provider =
                    new CachedNormalizedSphericalHarmonicsProvider(raw, step, nbPoints,
                            OrekitConfiguration.getCacheSlotsNumber(),
                            7 * Constants.JULIAN_DAY,
                            0.5 * Constants.JULIAN_DAY);
        }
        attractionModel = new HolmesFeatherstoneAttractionModel(centralBodyFrame, provider);
    }

    @Override
    public ForceModel getUnderlyingModel() {
        return attractionModel;
    }
}