TLEPropagatorBuilder.java

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package org.orekit.propagation.conversion;

import java.util.List;

import org.orekit.annotation.DefaultDataContext;
import org.orekit.attitudes.FrameAlignedProvider;
import org.orekit.data.DataContext;
import org.orekit.estimation.leastsquares.AbstractBatchLSModel;
import org.orekit.estimation.leastsquares.BatchLSModel;
import org.orekit.estimation.leastsquares.ModelObserver;
import org.orekit.estimation.measurements.ObservedMeasurement;
import org.orekit.frames.Frame;
import org.orekit.orbits.Orbit;
import org.orekit.orbits.PositionAngleType;
import org.orekit.propagation.Propagator;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.analytical.tle.TLE;
import org.orekit.propagation.analytical.tle.TLEPropagator;
import org.orekit.propagation.analytical.tle.generation.TleGenerationAlgorithm;
import org.orekit.utils.ParameterDriver;
import org.orekit.utils.ParameterDriversList;

/** Builder for TLEPropagator.
 * @author Pascal Parraud
 * @author Thomas Paulet
 * @since 6.0
 */
public class TLEPropagatorBuilder extends AbstractPropagatorBuilder {

    /** Data context used to access frames and time scales. */
    private final DataContext dataContext;

    /** Template TLE. */
    private final TLE templateTLE;

    /** TLE generation algorithm. */
    private final TleGenerationAlgorithm generationAlgorithm;

    /** Build a new instance. This constructor uses the {@link DataContext#getDefault()
     * default data context}.
     * <p>
     * The template TLE is used as a model to {@link
     * #createInitialOrbit() create initial orbit}. It defines the
     * inertial frame, the central attraction coefficient, orbit type, satellite number,
     * classification, .... and is also used together with the {@code positionScale} to
     * convert from the {@link ParameterDriver#setNormalizedValue(double) normalized}
     * parameters used by the callers of this builder to the real orbital parameters.
     * </p>
     * @param templateTLE reference TLE from which real orbits will be built
     * @param positionAngleType position angle type to use
     * @param positionScale scaling factor used for orbital parameters normalization
     * (typically set to the expected standard deviation of the position)
     * @param generationAlgorithm TLE generation algorithm
     * @since 12.0
     * @see #TLEPropagatorBuilder(TLE, PositionAngleType, double, DataContext, TleGenerationAlgorithm)
     */
    @DefaultDataContext
    public TLEPropagatorBuilder(final TLE templateTLE, final PositionAngleType positionAngleType,
                                final double positionScale, final TleGenerationAlgorithm generationAlgorithm) {
        this(templateTLE, positionAngleType, positionScale, DataContext.getDefault(), generationAlgorithm);
    }

    /** Build a new instance.
     * <p>
     * The template TLE is used as a model to {@link
     * #createInitialOrbit() create initial orbit}. It defines the
     * inertial frame, the central attraction coefficient, orbit type, satellite number,
     * classification, .... and is also used together with the {@code positionScale} to
     * convert from the {@link ParameterDriver#setNormalizedValue(double) normalized}
     * parameters used by the callers of this builder to the real orbital parameters.
     * The default attitude provider is aligned with the orbit's inertial frame.
     * </p>
     * @param templateTLE reference TLE from which real orbits will be built
     * @param positionAngleType position angle type to use
     * @param positionScale scaling factor used for orbital parameters normalization
     * (typically set to the expected standard deviation of the position)
     * @param dataContext used to access frames and time scales.
     * @param generationAlgorithm TLE generation algorithm
     * @since 12.0
     */
    public TLEPropagatorBuilder(final TLE templateTLE, final PositionAngleType positionAngleType,
                                final double positionScale, final DataContext dataContext,
                                final TleGenerationAlgorithm generationAlgorithm) {
        super(TLEPropagator.selectExtrapolator(templateTLE, dataContext.getFrames().getTEME()).getInitialState().getOrbit(),
                positionAngleType, positionScale, false, FrameAlignedProvider.of(dataContext.getFrames().getTEME()));

        // Supported parameters: Bstar
        addSupportedParameters(templateTLE.getParametersDrivers());

        this.templateTLE         = templateTLE;
        this.dataContext         = dataContext;
        this.generationAlgorithm = generationAlgorithm;
    }

    /** {@inheritDoc} */
    @Override
    public TLEPropagatorBuilder copy() {
        return new TLEPropagatorBuilder(templateTLE, getPositionAngleType(), getPositionScale(),
                                        dataContext, generationAlgorithm);
    }

    /** {@inheritDoc} */
    @Override
    public TLEPropagator buildPropagator(final double[] normalizedParameters) {

        // create the orbit
        setParameters(normalizedParameters);
        final Orbit           orbit = createInitialOrbit();
        final SpacecraftState state = new SpacecraftState(orbit);
        final Frame           teme  = dataContext.getFrames().getTEME();

        // TLE related to the orbit
        final TLE tle = generationAlgorithm.generate(state, templateTLE);
        final List<ParameterDriver> drivers = templateTLE.getParametersDrivers();
        for (int index = 0; index < drivers.size(); index++) {
            if (drivers.get(index).isSelected()) {
                tle.getParametersDrivers().get(index).setSelected(true);
            }
        }

        // propagator
        return TLEPropagator.selectExtrapolator(tle, getAttitudeProvider(), Propagator.DEFAULT_MASS, teme);

    }

    /** Getter for the template TLE.
     * @return the template TLE
     */
    public TLE getTemplateTLE() {
        return templateTLE;
    }

    /** {@inheritDoc} */
    @Override
    public AbstractBatchLSModel buildLeastSquaresModel(final PropagatorBuilder[] builders,
                                                       final List<ObservedMeasurement<?>> measurements,
                                                       final ParameterDriversList estimatedMeasurementsParameters,
                                                       final ModelObserver observer) {
        return new BatchLSModel(builders, measurements, estimatedMeasurementsParameters, observer);
    }

}