org.orekit.attitudes

Class YawCompensation

java.lang.Object

org.orekit.attitudes.GroundPointing

org.orekit.attitudes.YawCompensation

All Implemented Interfaces:

Serializable, AttitudeProvider, AttitudeProviderModifier

public class YawCompensation
extends GroundPointing
implements AttitudeProviderModifier

This class handles yaw compensation attitude provider.

Yaw compensation is mainly used for Earth observation satellites. As a satellites moves along its track, the image of ground points move on the focal point of the optical sensor. This motion is a combination of the satellite motion, but also on the Earth rotation and on the current attitude (in particular if the pointing includes Roll or Pitch offset). In order to reduce geometrical distortion, the yaw angle is changed a little from the simple ground pointing attitude such that the apparent motion of ground points is along a prescribed axis (orthogonal to the optical sensors rows), taking into account all effects.

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:

Véronique Pommier-Maurussane

See Also:

GroundPointing, Serialized Form

Constructor Summary

Constructors

Constructor and Description
YawCompensation(GroundPointing groundPointingLaw) Creates a new instance.

Method Summary

Methods

Modifier and Type	Method and Description
Attitude	getAttitude(PVCoordinatesProvider pvProv, AbsoluteDate date, Frame frame) Compute the attitude corresponding to an orbital state.
Attitude	getBaseState(PVCoordinatesProvider pvProv, AbsoluteDate date, Frame frame) Compute the base system state at given date, without compensation.
protected TimeStampedPVCoordinates	getTargetPV(PVCoordinatesProvider pvProv, AbsoluteDate date, Frame frame) Compute the target point position/velocity in specified frame.
AttitudeProvider	getUnderlyingAttitudeProvider() Get the underlying (ground pointing) attitude provider.
double	getYawAngle(PVCoordinatesProvider pvProv, AbsoluteDate date, Frame frame) Compute the yaw compensation angle at date.

Methods inherited from class org.orekit.attitudes.GroundPointing

getBodyFrame

Methods inherited from class java.lang.Object

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

Constructor Detail

YawCompensation

public YawCompensation(GroundPointing groundPointingLaw)

Creates a new instance.

Parameters:

groundPointingLaw - ground pointing attitude provider without yaw compensation

Method Detail

getUnderlyingAttitudeProvider

public AttitudeProvider getUnderlyingAttitudeProvider()

Get the underlying (ground pointing) attitude provider.

Specified by:

getUnderlyingAttitudeProvider in interface AttitudeProviderModifier

Returns:

underlying attitude provider, which in this case is a GroundPointing instance

getTargetPV

protected TimeStampedPVCoordinates getTargetPV(PVCoordinatesProvider pvProv,
                                   AbsoluteDate date,
                                   Frame frame)
                                        throws OrekitException

Compute the target point position/velocity in specified frame.

Specified by:

getTargetPV in class GroundPointing

Parameters:

pvProv - provider for PV coordinates

date - date at which target point is requested

frame - frame in which observed ground point should be provided

Returns:

observed ground point position (element 0) and velocity (at index 1) in specified frame

Throws:

OrekitException - if some specific error occurs, such as no target reached

getBaseState

public Attitude getBaseState(PVCoordinatesProvider pvProv,
                    AbsoluteDate date,
                    Frame frame)
                      throws OrekitException

Compute the base system state at given date, without compensation.

Parameters:

pvProv - provider for PV coordinates

date - date at which state is requested

frame - reference frame from which attitude is computed

Returns:

satellite base attitude state, i.e without compensation.

Throws:

OrekitException - if some specific error occurs

getAttitude

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

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 attitude on the specified date and position-velocity state

Throws:

OrekitException - if attitude cannot be computed

getYawAngle

public double getYawAngle(PVCoordinatesProvider pvProv,
                 AbsoluteDate date,
                 Frame frame)
                   throws OrekitException

Compute the yaw compensation angle at date.

Parameters:

pvProv - provider for PV coordinates

date - date at which compensation is requested

frame - reference frame from which attitude is computed

Returns:

yaw compensation angle for orbit.

Throws:

OrekitException - if some specific error occurs