TLEPropagatorBuilder.java
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* this work for additional information regarding copyright ownership.
* 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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* Unless required by applicable law or agreed to in writing, software
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package org.orekit.propagation.conversion;
import org.hipparchus.util.FastMath;
import org.hipparchus.util.MathUtils;
import org.orekit.annotation.DefaultDataContext;
import org.orekit.data.DataContext;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitInternalError;
import org.orekit.orbits.KeplerianOrbit;
import org.orekit.orbits.Orbit;
import org.orekit.orbits.OrbitType;
import org.orekit.orbits.PositionAngle;
import org.orekit.propagation.Propagator;
import org.orekit.propagation.analytical.tle.TLE;
import org.orekit.propagation.analytical.tle.TLEPropagator;
import org.orekit.utils.ParameterDriver;
import org.orekit.utils.ParameterObserver;
/** Builder for TLEPropagator.
* @author Pascal Parraud
* @since 6.0
*/
public class TLEPropagatorBuilder extends AbstractPropagatorBuilder {
/** Parameter name for B* coefficient. */
public static final String B_STAR = "BSTAR";
/** B* scaling factor.
* <p>
* We use a power of 2 to avoid numeric noise introduction
* in the multiplications/divisions sequences.
* </p>
*/
private static final double B_STAR_SCALE = FastMath.scalb(1.0, -20);
/** Satellite number. */
private final int satelliteNumber;
/** Classification (U for unclassified). */
private final char classification;
/** Launch year (all digits). */
private final int launchYear;
/** Launch number. */
private final int launchNumber;
/** Launch piece. */
private final String launchPiece;
/** Element number. */
private final int elementNumber;
/** Revolution number at epoch. */
private final int revolutionNumberAtEpoch;
/** Data context used to access frames and time scales. */
private final DataContext dataContext;
/** Ballistic coefficient. */
private double bStar;
/** 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 positionAngle position angle type to use
* @param positionScale scaling factor used for orbital parameters normalization
* (typically set to the expected standard deviation of the position)
* @since 7.1
* @see #TLEPropagatorBuilder(TLE, PositionAngle, double, DataContext)
*/
@DefaultDataContext
public TLEPropagatorBuilder(final TLE templateTLE, final PositionAngle positionAngle,
final double positionScale) {
this(templateTLE, positionAngle, positionScale, DataContext.getDefault());
}
/** 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.
* </p>
* @param templateTLE reference TLE from which real orbits will be built
* @param positionAngle 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.
* @since 10.1
*/
public TLEPropagatorBuilder(final TLE templateTLE,
final PositionAngle positionAngle,
final double positionScale,
final DataContext dataContext) {
super(TLEPropagator.selectExtrapolator(templateTLE, dataContext.getFrames())
.getInitialState().getOrbit(),
positionAngle, positionScale, false,
Propagator.getDefaultLaw(dataContext.getFrames()));
this.satelliteNumber = templateTLE.getSatelliteNumber();
this.classification = templateTLE.getClassification();
this.launchYear = templateTLE.getLaunchYear();
this.launchNumber = templateTLE.getLaunchNumber();
this.launchPiece = templateTLE.getLaunchPiece();
this.elementNumber = templateTLE.getElementNumber();
this.revolutionNumberAtEpoch = templateTLE.getRevolutionNumberAtEpoch();
this.bStar = 0.0;
this.dataContext = dataContext;
try {
final ParameterDriver driver = new ParameterDriver(B_STAR, bStar, B_STAR_SCALE,
Double.NEGATIVE_INFINITY,
Double.POSITIVE_INFINITY);
driver.addObserver(new ParameterObserver() {
/** {@inheritDoc} */
@Override
public void valueChanged(final double previousValue, final ParameterDriver driver) {
TLEPropagatorBuilder.this.bStar = driver.getValue();
}
});
addSupportedParameter(driver);
} catch (OrekitException oe) {
// this should never happen
throw new OrekitInternalError(oe);
}
}
/** {@inheritDoc} */
public Propagator buildPropagator(final double[] normalizedParameters) {
// create the orbit
setParameters(normalizedParameters);
final Orbit orbit = createInitialOrbit();
// we really need a Keplerian orbit type
final KeplerianOrbit kep = (KeplerianOrbit) OrbitType.KEPLERIAN.convertType(orbit);
final TLE tle = new TLE(satelliteNumber, classification, launchYear, launchNumber, launchPiece,
TLE.DEFAULT, elementNumber, orbit.getDate(),
kep.getKeplerianMeanMotion(), 0.0, 0.0,
kep.getE(), MathUtils.normalizeAngle(orbit.getI(), FastMath.PI),
MathUtils.normalizeAngle(kep.getPerigeeArgument(), FastMath.PI),
MathUtils.normalizeAngle(kep.getRightAscensionOfAscendingNode(), FastMath.PI),
MathUtils.normalizeAngle(kep.getMeanAnomaly(), FastMath.PI),
revolutionNumberAtEpoch, bStar,
dataContext.getTimeScales().getUTC());
return TLEPropagator.selectExtrapolator(
tle,
getAttitudeProvider(),
Propagator.DEFAULT_MASS,
dataContext.getFrames().getTEME());
}
}