TLEGradientConverter.java
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* CS licenses this file to You under the Apache License, Version 2.0
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package org.orekit.propagation.analytical.tle;
import java.util.ArrayList;
import java.util.List;
import org.hipparchus.analysis.differentiation.Gradient;
import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.orekit.attitudes.AttitudeProvider;
import org.orekit.attitudes.FieldAttitude;
import org.orekit.frames.Frame;
import org.orekit.orbits.FieldCartesianOrbit;
import org.orekit.orbits.FieldOrbit;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.integration.AbstractGradientConverter;
import org.orekit.time.TimeScale;
import org.orekit.utils.FieldAngularCoordinates;
import org.orekit.utils.FieldPVCoordinates;
import org.orekit.utils.ParameterDriver;
import org.orekit.utils.TimeStampedFieldAngularCoordinates;
import org.orekit.utils.TimeStampedFieldPVCoordinates;
/** Converter for TLE propagator.
* @author Luc Maisonobe
* @author Bryan Cazabonne
* @author Thomas Paulet
* @since 11.0
*/
class TLEGradientConverter extends AbstractGradientConverter {
/** Fixed dimension of the state. */
public static final int FREE_STATE_PARAMETERS = 6;
/** Current TLE. */
private final TLE tle;
/** UTC time scale. */
private final TimeScale utc;
/** TEME frame. */
private final Frame teme;
/** Attitude provider. */
private final AttitudeProvider provider;
/** States with various number of additional propagation parameters. */
private final List<FieldSpacecraftState<Gradient>> gStates;
/** Simple constructor.
* @param propagator TLE propagator used to access initial orbit
*/
TLEGradientConverter(final TLEPropagator propagator) {
super(FREE_STATE_PARAMETERS);
// TLE and related parameters
this.tle = propagator.getTLE();
this.teme = propagator.getFrame();
this.utc = tle.getUtc();
// Attitude provider
this.provider = propagator.getAttitudeProvider();
// Spacecraft state
final SpacecraftState state = propagator.getInitialState();
// Position always has derivatives
final Vector3D pos = state.getPVCoordinates().getPosition();
final FieldVector3D<Gradient> posG = new FieldVector3D<>(Gradient.variable(FREE_STATE_PARAMETERS, 0, pos.getX()),
Gradient.variable(FREE_STATE_PARAMETERS, 1, pos.getY()),
Gradient.variable(FREE_STATE_PARAMETERS, 2, pos.getZ()));
// Velocity may have derivatives or not
final Vector3D vel = state.getPVCoordinates().getVelocity();
final FieldVector3D<Gradient> velG = new FieldVector3D<>(Gradient.variable(FREE_STATE_PARAMETERS, 3, vel.getX()),
Gradient.variable(FREE_STATE_PARAMETERS, 4, vel.getY()),
Gradient.variable(FREE_STATE_PARAMETERS, 5, vel.getZ()));
// Acceleration never has derivatives
final Vector3D acc = state.getPVCoordinates().getAcceleration();
final FieldVector3D<Gradient> accG = new FieldVector3D<>(Gradient.constant(FREE_STATE_PARAMETERS, acc.getX()),
Gradient.constant(FREE_STATE_PARAMETERS, acc.getY()),
Gradient.constant(FREE_STATE_PARAMETERS, acc.getZ()));
// Mass never has derivatives
final Gradient gM = Gradient.constant(FREE_STATE_PARAMETERS, state.getMass());
final Gradient gMu = Gradient.constant(FREE_STATE_PARAMETERS, TLEPropagator.getMU());
final FieldOrbit<Gradient> gOrbit =
new FieldCartesianOrbit<>(new TimeStampedFieldPVCoordinates<>(state.getDate(), posG, velG, accG),
state.getFrame(), gMu);
// Attitude
final FieldAttitude<Gradient> gAttitude = provider.getAttitude(gOrbit, gOrbit.getDate(), gOrbit.getFrame());
// Initialize the list with the state having 0 force model parameters
gStates = new ArrayList<>();
gStates.add(new FieldSpacecraftState<>(gOrbit, gAttitude, gM));
}
/** Get the state with the number of parameters consistent with TLE model.
* @return state with the number of parameters consistent with TLE model
*/
public FieldSpacecraftState<Gradient> getState() {
// Count the required number of parameters
int nbParams = 0;
for (final ParameterDriver driver : tle.getParametersDrivers()) {
if (driver.isSelected()) {
++nbParams;
}
}
// Fill in intermediate slots
while (gStates.size() < nbParams + 1) {
gStates.add(null);
}
if (gStates.get(nbParams) == null) {
// It is the first time we need this number of parameters
// We need to create the state
final int freeParameters = FREE_STATE_PARAMETERS + nbParams;
final FieldSpacecraftState<Gradient> s0 = gStates.get(0);
// Orbit
final FieldPVCoordinates<Gradient> pv0 = s0.getPVCoordinates();
final FieldOrbit<Gradient> gOrbit =
new FieldCartesianOrbit<>(new TimeStampedFieldPVCoordinates<>(s0.getDate().toAbsoluteDate(),
extend(pv0.getPosition(), freeParameters),
extend(pv0.getVelocity(), freeParameters),
extend(pv0.getAcceleration(), freeParameters)),
s0.getFrame(),
extend(s0.getMu(), freeParameters));
// Attitude
final FieldAngularCoordinates<Gradient> ac0 = s0.getAttitude().getOrientation();
final FieldAttitude<Gradient> gAttitude =
new FieldAttitude<>(s0.getAttitude().getReferenceFrame(),
new TimeStampedFieldAngularCoordinates<>(gOrbit.getDate(),
extend(ac0.getRotation(), freeParameters),
extend(ac0.getRotationRate(), freeParameters),
extend(ac0.getRotationAcceleration(), freeParameters)));
// Mass
final Gradient gM = extend(s0.getMass(), freeParameters);
gStates.set(nbParams, new FieldSpacecraftState<>(gOrbit, gAttitude, gM));
}
return gStates.get(nbParams);
}
/** Get the model parameters.
* @param state state as returned by {@link #getState(TLE)}
* @return TLE model parameters
*/
public Gradient[] getParameters(final FieldSpacecraftState<Gradient> state) {
final int freeParameters = state.getMass().getFreeParameters();
final List<ParameterDriver> drivers = tle.getParametersDrivers();
final Gradient[] parameters = new Gradient[drivers.size()];
int index = FREE_STATE_PARAMETERS;
int i = 0;
for (ParameterDriver driver : drivers) {
parameters[i++] = driver.isSelected() ?
Gradient.variable(freeParameters, index++, driver.getValue()) :
Gradient.constant(freeParameters, driver.getValue());
}
return parameters;
}
/** Get the converted TLE propagator.
* @param state state as returned by {@link #getState(TLE)}
* @param parameters model parameters as returned by {@link #getParameters(FieldSpacecraftState, TLE)}
* @return the converted propagator
*/
public FieldTLEPropagator<Gradient> getPropagator(final FieldSpacecraftState<Gradient> state,
final Gradient[] parameters) {
// Zero
final Gradient zero = state.getA().getField().getZero();
// Template TLE
final int satelliteNumber = tle.getSatelliteNumber();
final char classification = tle.getClassification();
final int launchYear = tle.getLaunchYear();
final int launchNumber = tle.getLaunchNumber();
final String launchPiece = tle.getLaunchPiece();
final int ephemerisType = tle.getEphemerisType();
final int elementNumber = tle.getElementNumber();
final int revolutionNumberAtEpoch = tle.getRevolutionNumberAtEpoch();
final double bStar = tle.getBStar();
// Initialize the new TLE
final FieldTLE<Gradient> templateTLE = new FieldTLE<>(satelliteNumber, classification,
launchYear, launchNumber, launchPiece, ephemerisType, elementNumber, state.getDate(),
zero, zero, zero, zero, zero, zero, zero, zero,
revolutionNumberAtEpoch, bStar, utc);
// TLE
final FieldTLE<Gradient> gTLE = FieldTLE.stateToTLE(state, templateTLE, utc, teme);
// Return the "Field" propagator
return FieldTLEPropagator.selectExtrapolator(gTLE, provider, state.getMass(), teme, parameters);
}
}