Galileo.java
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package org.orekit.gnss.attitude;
import org.hipparchus.Field;
import org.hipparchus.RealFieldElement;
import org.hipparchus.analysis.differentiation.DerivativeStructure;
import org.hipparchus.analysis.differentiation.FieldDerivativeStructure;
import org.hipparchus.util.FastMath;
import org.hipparchus.util.FieldSinCos;
import org.orekit.frames.Frame;
import org.orekit.time.AbsoluteDate;
import org.orekit.utils.ExtendedPVCoordinatesProvider;
import org.orekit.utils.TimeStampedAngularCoordinates;
import org.orekit.utils.TimeStampedFieldAngularCoordinates;
/**
* Attitude providers for Galileo navigation satellites.
* <p>
* This class is based on the May 2017 version of J. Kouba eclips.f
* subroutine available at <a href="http://acc.igs.org/orbits">IGS Analysis
* Center Coordinator site</a>. The eclips.f code itself is not used ; its
* hard-coded data are used and its low level models are used, but the
* structure of the code and the API have been completely rewritten.
* </p>
* @author J. Kouba original fortran routine
* @author Luc Maisonobe Java translation
* @since 9.2
*/
public class Galileo extends AbstractGNSSAttitudeProvider {
/** Default yaw rates for all spacecrafts in radians per seconds. */
public static final double DEFAULT_YAW_RATE = FastMath.toRadians(0.203);
/** Constants for Galileo turns. */
private static final double BETA_X = FastMath.toRadians(15.0);
/** Limit for the noon turn. */
private static final double COS_NOON = FastMath.cos(BETA_X);
/** Limit for the night turn. */
private static final double COS_NIGHT = -COS_NOON;
/** No margin on turn end for Galileo. */
private static final double END_MARGIN = 0.0;
/** Yaw rate. */
private final double yawRate;
/** Simple constructor.
* @param yawRate yaw rate to use in radians per seconds (typically {@link #DEFAULT_YAW_RATE})
* @param validityStart start of validity for this provider
* @param validityEnd end of validity for this provider
* @param sun provider for Sun position
* @param inertialFrame inertial frame where velocity are computed
*/
public Galileo(final double yawRate,
final AbsoluteDate validityStart, final AbsoluteDate validityEnd,
final ExtendedPVCoordinatesProvider sun, final Frame inertialFrame) {
super(validityStart, validityEnd, sun, inertialFrame);
this.yawRate = yawRate;
}
/** {@inheritDoc} */
@Override
protected TimeStampedAngularCoordinates correctedYaw(final GNSSAttitudeContext context) {
// noon beta angle limit from yaw rate
final double beta0 = FastMath.atan(context.getMuRate() / yawRate);
if (FastMath.abs(context.beta(context.getDate())) < beta0 &&
context.setUpTurnRegion(COS_NIGHT, COS_NOON)) {
context.setHalfSpan(context.inSunSide() ?
BETA_X :
context.inOrbitPlaneAbsoluteAngle(BETA_X),
END_MARGIN);
if (context.inTurnTimeRange()) {
// handling both noon and midnight turns at once
final DerivativeStructure beta = context.betaDS();
final FieldSinCos<DerivativeStructure> scBeta = FastMath.sinCos(beta);
final DerivativeStructure cosBeta = scBeta.cos();
final DerivativeStructure sinBeta = scBeta.sin();
final double sinY = FastMath.copySign(FastMath.sin(beta0), context.getSecuredBeta());
final DerivativeStructure sd = FastMath.sin(context.getDeltaDS()).
multiply(FastMath.copySign(1.0, -context.getSVBcos() * context.getDeltaDS().getPartialDerivative(1)));
final DerivativeStructure c = sd.multiply(cosBeta);
final DerivativeStructure shy = sinBeta.negate().subtract(sinY).
add(sinBeta.subtract(sinY).multiply(c.abs().multiply(FastMath.PI / FastMath.sin(BETA_X)).cos())).
multiply(0.5);
final DerivativeStructure phi = FastMath.atan2(shy, c);
return context.turnCorrectedAttitude(phi);
}
}
// in nominal yaw mode
return context.nominalYaw(context.getDate());
}
/** {@inheritDoc} */
@Override
protected <T extends RealFieldElement<T>> TimeStampedFieldAngularCoordinates<T> correctedYaw(final GNSSFieldAttitudeContext<T> context) {
// noon beta angle limit from yaw rate
final double beta0 = FastMath.atan(context.getMuRate().getReal() / yawRate);
if (FastMath.abs(context.beta(context.getDate())).getReal() < beta0 &&
context.setUpTurnRegion(COS_NIGHT, COS_NOON)) {
final Field<T> field = context.getDate().getField();
final T betaX = field.getZero().add(BETA_X);
context.setHalfSpan(context.inSunSide() ?
betaX :
context.inOrbitPlaneAbsoluteAngle(betaX),
END_MARGIN);
if (context.inTurnTimeRange()) {
// handling both noon and midnight turns at once
final FieldDerivativeStructure<T> beta = context.betaDS();
final FieldSinCos<FieldDerivativeStructure<T>> scBeta = FastMath.sinCos(beta);
final FieldDerivativeStructure<T> cosBeta = scBeta.cos();
final FieldDerivativeStructure<T> sinBeta = scBeta.sin();
final T sinY = FastMath.sin(field.getZero().add(beta0)).copySign(context.getSecuredBeta());
final FieldDerivativeStructure<T> sd = FastMath.sin(context.getDeltaDS()).
multiply(FastMath.copySign(1.0, -context.getSVBcos().getReal() * context.getDeltaDS().getPartialDerivative(1).getReal()));
final FieldDerivativeStructure<T> c = sd.multiply(cosBeta);
final FieldDerivativeStructure<T> shy = sinBeta.negate().subtract(sinY).
add(sinBeta.subtract(sinY).multiply(c.abs().multiply(FastMath.PI / FastMath.sin(BETA_X)).cos())).
multiply(0.5);
final FieldDerivativeStructure<T> phi = FastMath.atan2(shy, c);
return context.turnCorrectedAttitude(phi);
}
}
// in nominal yaw mode
return context.nominalYaw(context.getDate());
}
}