org.orekit.attitudes
Class GroundPointing

java.lang.Object
  org.orekit.attitudes.AbstractAttitudeLaw
      org.orekit.attitudes.GroundPointing

All Implemented Interfaces:

Serializable, AttitudeLaw, AttitudeProvider

Direct Known Subclasses:

BodyCenterGroundPointing, GroundPointingWrapper, LofOffsetPointing, NadirPointing, TargetGroundPointing

public abstract class GroundPointing
extends AbstractAttitudeLaw

Base class for ground pointing attitude providers.

This class is a basic model for different kind of ground pointing attitude providers, such as : body center pointing, nadir pointing, target pointing, etc...

The object GroundPointing is guaranteed to be immutable.

Author:

Véronique Pommier-Maurussane

See Also:

AttitudeProvider, Serialized Form

Constructor Summary

protected

GroundPointing(BodyShape shape) Default constructor.

Method Summary

Attitude	getAttitude(PVCoordinatesProvider pvProv, AbsoluteDate date, Frame frame) Compute the attitude corresponding to an orbital state.
Frame	getBodyFrame() Get the body frame.
BodyShape	getBodyShape() Get the body shape.
protected abstract Vector3D	getTargetPoint(PVCoordinatesProvider pvProv, AbsoluteDate date, Frame frame) Compute the target point in specified frame.
protected TimeStampedPVCoordinates	getTargetPV(PVCoordinatesProvider pvProv, AbsoluteDate date, Frame frame) Compute the target point position/velocity in specified frame.

Methods inherited from class org.orekit.attitudes.AbstractAttitudeLaw

getAttitude, getSpinDerivativesComputation, setSpinDerivativesComputation

Methods inherited from class java.lang.Object

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

Constructor Detail

GroundPointing

protected GroundPointing(BodyShape shape)

Default constructor. Build a new instance with arbitrary default elements.

Parameters:

shape - the body shape

Method Detail

getAttitude

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

Compute the attitude corresponding to an orbital state.

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

getTargetPoint

protected abstract Vector3D getTargetPoint(PVCoordinatesProvider pvProv,
                                           AbsoluteDate date,
                                           Frame frame)
                                    throws OrekitException

Compute the target point in specified frame.

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 in specified frame

Throws:

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

getTargetPV

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

Compute the target point position/velocity in specified frame.

The default implementation use a simple centered two points finite differences scheme, it may be replaced by more accurate models in specialized implementations.

In the case where the point is computed at a date corresponding to the lower/upper bound of the ephemeris, the finite differences scheme used is either 1st order forward or backward.

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/velocity in specified frame

Throws:

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

getBodyFrame

public final Frame getBodyFrame()

Get the body frame.

Returns:

body frame

getBodyShape

public final BodyShape getBodyShape()

Get the body shape.

Returns:

body shape