DSSTGradientConverter.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.semianalytical.dsst;
import org.hipparchus.analysis.differentiation.Gradient;
import org.orekit.attitudes.AttitudeProvider;
import org.orekit.attitudes.FieldAttitude;
import org.orekit.orbits.FieldEquinoctialOrbit;
import org.orekit.orbits.FieldOrbit;
import org.orekit.orbits.PositionAngleType;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.integration.AbstractGradientConverter;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.FieldAbsoluteDate;
/** Converter for states and parameters arrays.
* @author Luc Maisonobe
* @author Bryan Cazabonne
* @since 10.2
*/
class DSSTGradientConverter extends AbstractGradientConverter {
/** Fixed dimension of the state. */
private static final int FREE_STATE_PARAMETERS = 6;
/** Simple constructor.
* @param state regular state
* @param provider provider to use if attitude needs to be recomputed
*/
DSSTGradientConverter(final SpacecraftState state, final AttitudeProvider provider) {
super(FREE_STATE_PARAMETERS);
// equinoctial parameters always has derivatives
final Gradient sma = Gradient.variable(FREE_STATE_PARAMETERS, 0, state.getA());
final Gradient ex = Gradient.variable(FREE_STATE_PARAMETERS, 1, state.getEquinoctialEx());
final Gradient ey = Gradient.variable(FREE_STATE_PARAMETERS, 2, state.getEquinoctialEy());
final Gradient hx = Gradient.variable(FREE_STATE_PARAMETERS, 3, state.getHx());
final Gradient hy = Gradient.variable(FREE_STATE_PARAMETERS, 4, state.getHy());
final Gradient l = Gradient.variable(FREE_STATE_PARAMETERS, 5, state.getLM());
final Gradient gMu = Gradient.constant(FREE_STATE_PARAMETERS, state.getMu());
// date
final AbsoluteDate date = state.getDate();
final FieldAbsoluteDate<Gradient> dateField = new FieldAbsoluteDate<>(sma.getField(), date);
// mass never has derivatives
final Gradient gM = Gradient.constant(FREE_STATE_PARAMETERS, state.getMass());
final FieldOrbit<Gradient> gOrbit =
new FieldEquinoctialOrbit<>(sma, ex, ey, hx, hy, l,
PositionAngleType.MEAN,
state.getFrame(),
dateField,
gMu);
final FieldAttitude<Gradient> gAttitude;
// compute attitude partial derivatives
gAttitude = provider.getAttitude(gOrbit, gOrbit.getDate(), gOrbit.getFrame());
// initialize the list with the state having 0 force model parameters
initStates(new FieldSpacecraftState<>(gOrbit, gAttitude, gM));
}
}