fr.cnes.sirius.patrius.attitudes

Class YawSteering

java.lang.Object

fr.cnes.sirius.patrius.attitudes.AbstractAttitudeLaw

fr.cnes.sirius.patrius.attitudes.AbstractGroundPointing

fr.cnes.sirius.patrius.attitudes.AbstractGroundPointingWrapper

fr.cnes.sirius.patrius.attitudes.YawSteering

All Implemented Interfaces:

AttitudeLaw, AttitudeLawModifier, AttitudeProvider, Serializable

public class YawSteering
extends AbstractGroundPointingWrapper

This class handles yaw steering law.

Yaw steering is mainly used for low Earth orbiting satellites with no missions-related constraints on yaw angle. It sets the yaw angle in such a way the solar arrays have maximal lightning without changing the roll and pitch.

The motion in yaw is smooth when the Sun is far from the orbital plane, but gets more and more square like as the Sun gets closer to the orbital plane. The degenerate extreme case with the Sun in the orbital plane leads to a yaw angle switching between two steady states, with instantaneaous π radians rotations at each switch, two times per orbit. This degenerate case is clearly not operationally sound so another pointing mode is chosen when Sun comes closer than some predefined threshold to the orbital plane.

This class can handle (for now) only a theoretically perfect yaw steering (i.e. the yaw angle is exactly the optimal angle). Smoothed yaw steering with a few sine waves approaching the optimal angle will be added in the future if needed.

This attitude is implemented as a wrapper on top of an underlying ground pointing law that defines the roll and pitch angles.

Instances of this class are guaranteed to be immutable.

Author:

Luc Maisonobe

See Also:

GroundPointing, Serialized Form

Constructor Summary

Constructors

Constructor and Description
YawSteering(AbstractGroundPointing groundPointingLaw, PVCoordinatesProvider sunIn, Vector3D phasingAxisIn) Creates a new instance.
YawSteering(AbstractGroundPointing groundPointingLaw, PVCoordinatesProvider sunIn, Vector3D phasingAxisIn, Vector3D losInSatFrameVec, Vector3D losNormalInSatFrameVec) Constructor.

Method Summary

Modifier and Type	Method and Description
Attitude	getAttitude(PVCoordinatesProvider pvProv, AbsoluteDate date, Frame frame) Compute the attitude corresponding to an orbital state.
TimeStampedAngularCoordinates	getCompensation(PVCoordinatesProvider pvProv, AbsoluteDate date, Frame orbitFrame, Attitude base) Compute the TimeStampedAngularCoordinates at a given time.
Vector3D	getPhasingAxis() Getter for the satellite axis that must be roughly in Sun direction.
PVCoordinatesProvider	getSun() Returns the Sun.
String	toString()

Methods inherited from class fr.cnes.sirius.patrius.attitudes.AbstractGroundPointingWrapper

getBaseState, getGroundPointingLaw, getTargetPoint, getTargetPV, getUnderlyingAttitudeLaw, setSpinDerivativesComputation

Methods inherited from class fr.cnes.sirius.patrius.attitudes.AbstractGroundPointing

getBodyFrame, getBodyShape, getLosInSatFrame, getLosNormalInSatFrame

Methods inherited from class fr.cnes.sirius.patrius.attitudes.AbstractAttitudeLaw

getSpinDerivativesComputation

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface fr.cnes.sirius.patrius.attitudes.AttitudeProvider

computeSpinByFD, computeSpinDerivativeByFD, getAttitude

Constructor Detail

YawSteering

public YawSteering(AbstractGroundPointing groundPointingLaw,
                   PVCoordinatesProvider sunIn,
                   Vector3D phasingAxisIn)

Creates a new instance.

Parameters:

groundPointingLaw - ground pointing attitude provider without yaw compensation

sunIn - sun motion model

phasingAxisIn - satellite axis that must be roughly in Sun direction (if solar arrays rotation axis is Y, then this axis should be either +X or -X)

YawSteering

public YawSteering(AbstractGroundPointing groundPointingLaw,
                   PVCoordinatesProvider sunIn,
                   Vector3D phasingAxisIn,
                   Vector3D losInSatFrameVec,
                   Vector3D losNormalInSatFrameVec)

Constructor. Create a BodyCenterGroundPointing attitude provider with specified los axis in satellite frame.

Parameters:

groundPointingLaw - ground pointing attitude provider without yaw compensation

sunIn - sun motion model

phasingAxisIn - satellite axis that must be roughly in Sun direction (if solar arrays rotation axis is Y, then this axis should be either +X or -X)

losInSatFrameVec - LOS in satellite frame axis

losNormalInSatFrameVec - LOS normal axis in satellite frame

Method Detail

getAttitude

public Attitude getAttitude(PVCoordinatesProvider pvProv,
                            AbsoluteDate date,
                            Frame frame)
                     throws PatriusException

Compute the attitude corresponding to an orbital state.

Specified by:

getAttitude in interface AttitudeProvider

Overrides:

getAttitude in class AbstractGroundPointing

Parameters:

pvProv - local position-velocity provider around current date

date - current date

frame - reference frame from which attitude is computed

Returns:

attitude attitude on the specified date and position-velocity state

Throws:

PatriusException - if attitude cannot be computed for provided date

getCompensation

public TimeStampedAngularCoordinates getCompensation(PVCoordinatesProvider pvProv,
                                                     AbsoluteDate date,
                                                     Frame orbitFrame,
                                                     Attitude base)
                                              throws PatriusException

Compute the TimeStampedAngularCoordinates at a given time.

Specified by:

getCompensation in class AbstractGroundPointingWrapper

Parameters:

pvProv - provider for PV coordinates

date - date at which rotation is requested

orbitFrame - reference frame from which attitude is computed

base - base satellite attitude in given frame.

Returns:

compensation rotation at date, i.e rotation between non compensated attitude state and compensated state.

Throws:

PatriusException - if some specific error occurs

getPhasingAxis

public Vector3D getPhasingAxis()

Getter for the satellite axis that must be roughly in Sun direction.

Returns:

the satellite axis that must be roughly in Sun direction.

getSun

public PVCoordinatesProvider getSun()

Returns the Sun.

Returns:

the Sun

toString

public String toString()

Overrides:

toString in class Object