Galileo.java
/* Copyright 2002-2018 CS Systèmes d'Information
* Licensed to CS Systèmes d'Information (CS) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* CS licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
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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.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>
* <p>
* WARNING: as of release 9.2, this feature is still considered experimental
* </p>
* @author J. Kouba original fortran routine
* @author Luc Maisonobe Java translation
* @since 9.2
*/
public class Galileo extends AbstractGNSSAttitudeProvider {
/** Serializable UID. */
private static final long serialVersionUID = 20171114L;
/** Constants for Galileo turns. */
private static final double BETA_X = FastMath.toRadians(15.0);
/** Constants for Galileo turns. */
private static final double BETA_Y = FastMath.toRadians(2.0);
/** 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 final double END_MARGIN = 0.0;
/** Simple constructor.
* @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 AbsoluteDate validityStart, final AbsoluteDate validityEnd,
final ExtendedPVCoordinatesProvider sun, final Frame inertialFrame) {
super(validityStart, validityEnd, sun, inertialFrame);
}
/** {@inheritDoc} */
@Override
protected TimeStampedAngularCoordinates correctedYaw(final GNSSAttitudeContext context) {
if (FastMath.abs(context.getBeta()) < BETA_Y &&
context.setUpTurnRegion(COS_NIGHT, COS_NOON)) {
context.setHalfSpan(context.inSunSide() ?
BETA_X :
context.inOrbitPlaneAbsoluteAngle(BETA_X));
if (context.inTurnTimeRange(context.getDate(), END_MARGIN)) {
// handling both noon and midnight turns at once
final DerivativeStructure beta = context.getBetaDS();
final DerivativeStructure cosBeta = beta.cos();
final DerivativeStructure sinBeta = beta.sin();
final double sinY = FastMath.copySign(FastMath.sin(BETA_Y), 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.getNominalYaw();
}
/** {@inheritDoc} */
@Override
protected <T extends RealFieldElement<T>> TimeStampedFieldAngularCoordinates<T> correctedYaw(final GNSSFieldAttitudeContext<T> context) {
if (FastMath.abs(context.getBeta()).getReal() < BETA_Y &&
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));
if (context.inTurnTimeRange(context.getDate(), END_MARGIN)) {
// handling both noon and midnight turns at once
final FieldDerivativeStructure<T> beta = context.getBetaDS();
final FieldDerivativeStructure<T> cosBeta = beta.cos();
final FieldDerivativeStructure<T> sinBeta = beta.sin();
final T sinY = FastMath.sin(field.getZero().add(BETA_Y)).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.getNominalYaw();
}
}