Package org.orekit.attitudes

Class Attitude

java.lang.Object

org.orekit.attitudes.Attitude

All Implemented Interfaces:

Serializable, TimeInterpolable<Attitude>, TimeShiftable<Attitude>, TimeStamped

public class Attitude
extends Object
implements TimeStamped, TimeShiftable<Attitude>, TimeInterpolable<Attitude>, Serializable

This class handles attitude definition at a given date.

This class represents the rotation between a reference frame and the satellite frame, as well as the spin of the satellite (axis and rotation rate).

The state can be slightly shifted to close dates. This shift is based on a linear extrapolation for attitude taking the spin rate into account. It is not intended as a replacement for proper attitude propagation but should be sufficient for either small time shifts or coarse accuracy.

The instance Attitude is guaranteed to be immutable.

Author:

Véronique Pommier-Maurussane

See Also:

Orbit, AttitudeProvider, Serialized Form

Constructor Summary

Constructors

Constructor	Description
Attitude(Frame referenceFrame, TimeStampedAngularCoordinates orientation)	Creates a new instance.
Attitude(AbsoluteDate date, Frame referenceFrame, Rotation attitude, Vector3D spin, Vector3D acceleration)	Creates a new instance.
Attitude(AbsoluteDate date, Frame referenceFrame, AngularCoordinates orientation)	Creates a new instance.

Method Summary

Modifier and Type	Method	Description
AbsoluteDate	getDate()	Get the date of attitude parameters.
TimeStampedAngularCoordinates	getOrientation()	Get the complete orientation including spin.
Frame	getReferenceFrame()	Get the reference frame.
Rotation	getRotation()	Get the attitude rotation.
Vector3D	getRotationAcceleration()	Get the satellite rotation acceleration.
Vector3D	getSpin()	Get the satellite spin.
Attitude	interpolate(AbsoluteDate interpolationDate, Stream<Attitude> sample)	Get an interpolated instance.
Attitude	shiftedBy(double dt)	Get a time-shifted attitude.
Attitude	withReferenceFrame(Frame newReferenceFrame)	Get a similar attitude with a specific reference frame.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.orekit.time.TimeInterpolable

interpolate

Constructor Detail

Attitude

public Attitude(Frame referenceFrame,
                TimeStampedAngularCoordinates orientation)

Creates a new instance.

Parameters:

referenceFrame - reference frame from which attitude is defined

orientation - complete orientation between reference frame and satellite frame, including rotation rate

Attitude

public Attitude(AbsoluteDate date,
                Frame referenceFrame,
                AngularCoordinates orientation)

Creates a new instance.

Parameters:

date - date at which attitude is defined

referenceFrame - reference frame from which attitude is defined

orientation - complete orientation between reference frame and satellite frame, including rotation rate

Attitude

public Attitude(AbsoluteDate date,
                Frame referenceFrame,
                Rotation attitude,
                Vector3D spin,
                Vector3D acceleration)

Creates a new instance.

Parameters:

date - date at which attitude is defined

referenceFrame - reference frame from which attitude is defined

attitude - rotation between reference frame and satellite frame

spin - satellite spin (axis and velocity, in satellite frame)

acceleration - satellite rotation acceleration (in satellite frame)

Method Detail

shiftedBy

public Attitude shiftedBy(double dt)

Get a time-shifted attitude.

The state can be slightly shifted to close dates. This shift is based on a linear extrapolation for attitude taking the spin rate into account. It is not intended as a replacement for proper attitude propagation but should be sufficient for either small time shifts or coarse accuracy.

Specified by:

shiftedBy in interface TimeShiftable<Attitude>

Parameters:

dt - time shift in seconds

Returns:

a new attitude, shifted with respect to the instance (which is immutable)

withReferenceFrame

public Attitude withReferenceFrame(Frame newReferenceFrame)
                            throws OrekitException

Get a similar attitude with a specific reference frame.

If the instance reference frame is already the specified one, the instance itself is returned without any object creation. Otherwise, a new instance will be created with the specified reference frame. In this case, the required intermediate rotation and spin between the specified and the original reference frame will be inserted.

Parameters:

newReferenceFrame - desired reference frame for attitude

Returns:

an attitude that has the same orientation and motion as the instance, but guaranteed to have the specified reference frame

Throws:

OrekitException - if conversion between reference frames fails

getDate

public AbsoluteDate getDate()

Get the date of attitude parameters.

Specified by:

getDate in interface TimeStamped

Returns:

date of the attitude parameters

getReferenceFrame

public Frame getReferenceFrame()

Get the reference frame.

Returns:

referenceFrame reference frame from which attitude is defined.

getOrientation

public TimeStampedAngularCoordinates getOrientation()

Get the complete orientation including spin.

Returns:

complete orientation including spin

See Also:

getRotation(), getSpin()

getRotation

public Rotation getRotation()

Get the attitude rotation.

Returns:

attitude satellite rotation from reference frame.

See Also:

getOrientation(), getSpin()

getSpin

public Vector3D getSpin()

Get the satellite spin.

The spin vector is defined in satellite frame.

Returns:

spin satellite spin (axis and velocity).

See Also:

getOrientation(), getRotation()

getRotationAcceleration

public Vector3D getRotationAcceleration()

Get the satellite rotation acceleration.

The rotation acceleration. vector is defined in satellite frame.

Returns:

rotation acceleration

See Also:

getOrientation(), getRotation()

interpolate

public Attitude interpolate(AbsoluteDate interpolationDate,
                            Stream<Attitude> sample)
                     throws OrekitException

Get an interpolated instance.

Note that the state of the current instance may not be used in the interpolation process, only its type and non interpolable fields are used (for example central attraction coefficient or frame when interpolating orbits). The interpolable fields taken into account are taken only from the states of the sample points. So if the state of the instance must be used, the instance should be included in the sample points.

Note that this method is designed for small samples only (say up to about 10-20 points) so it can be implemented using polynomial interpolation (typically Hermite interpolation). Using too much points may induce Runge's phenomenon and numerical problems (including NaN appearing).

The interpolated instance is created by polynomial Hermite interpolation on Rodrigues vector ensuring rotation rate remains the exact derivative of rotation.

As this implementation of interpolation is polynomial, it should be used only with small samples (about 10-20 points) in order to avoid Runge's phenomenon and numerical problems (including NaN appearing).

Specified by:

interpolate in interface TimeInterpolable<Attitude>

Parameters:

interpolationDate - interpolation date

sample - sample points on which interpolation should be done

Returns:

a new instance, interpolated at specified date

Throws:

OrekitException - if the number of point is too small for interpolating