Package org.orekit.attitudes

Class YawSteering

java.lang.Object

org.orekit.attitudes.GroundPointing

org.orekit.attitudes.GroundPointingAttitudeModifier

org.orekit.attitudes.YawSteering

All Implemented Interfaces:

AttitudeProvider, AttitudeProviderModifier

public class YawSteering
extends GroundPointingAttitudeModifier
implements AttitudeProviderModifier

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 lighting 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 instantaneous 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

Constructor Summary

Constructors

Constructor	Description
YawSteering(Frame inertialFrame, GroundPointing groundPointingLaw, PVCoordinatesProvider sun, Vector3D phasingAxis)	Creates a new instance.

Method Summary

Modifier and Type	Method	Description
<T extends CalculusFieldElement<T>> FieldAttitude<T>	getAttitude(FieldPVCoordinatesProvider<T> pvProv, FieldAbsoluteDate<T> date, Frame frame)	Compute the attitude corresponding to an orbital state.
Attitude	getAttitude(PVCoordinatesProvider pvProv, AbsoluteDate date, Frame frame)	Compute the attitude corresponding to an orbital state.

Methods inherited from class org.orekit.attitudes.GroundPointingAttitudeModifier

getBaseState, getBaseState, getTargetPosition, getTargetPosition, getTargetPV, getTargetPV, getUnderlyingAttitudeProvider

Methods inherited from class org.orekit.attitudes.GroundPointing

getAttitudeRotation, getAttitudeRotation, getBodyFrame

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.orekit.attitudes.AttitudeProvider

getAttitudeRotation, getAttitudeRotation

Methods inherited from interface org.orekit.attitudes.AttitudeProviderModifier

getUnderlyingAttitudeProvider

Constructor Detail

YawSteering

public YawSteering(Frame inertialFrame,
                   GroundPointing groundPointingLaw,
                   PVCoordinatesProvider sun,
                   Vector3D phasingAxis)

Creates a new instance.

Parameters:

inertialFrame - frame in which orbital velocities are computed

groundPointingLaw - ground pointing attitude provider without yaw compensation

sun - sun motion model

phasingAxis - 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)

Since:

7.1

Method Detail

getAttitude

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

Compute the attitude corresponding to an orbital state.

Specified by:

getAttitude in interface AttitudeProvider

Overrides:

getAttitude in class GroundPointing

Parameters:

pvProv - local position-velocity provider around current date

date - current date

frame - reference frame from which attitude is computed

Returns:

attitude on the specified date and position-velocity state

getAttitude

public <T extends CalculusFieldElement<T>> FieldAttitude<T> getAttitude(FieldPVCoordinatesProvider<T> pvProv,
                                                                        FieldAbsoluteDate<T> date,
                                                                        Frame frame)

Compute the attitude corresponding to an orbital state.

Specified by:

getAttitude in interface AttitudeProvider

Overrides:

getAttitude in class GroundPointing

Type Parameters:

T - type of the field elements

Parameters:

pvProv - local position-velocity provider around current date

date - current date

frame - reference frame from which attitude is computed

Returns:

attitude on the specified date and position-velocity state