org.orekit.utils

Class TimeStampedFieldAngularCoordinates<T extends RealFieldElement<T>>

java.lang.Object

org.orekit.utils.FieldAngularCoordinates<T>

org.orekit.utils.TimeStampedFieldAngularCoordinates<T>

Type Parameters:

T - the type of the field elements

All Implemented Interfaces:

Serializable, TimeShiftable<FieldAngularCoordinates<T>>, TimeStamped

public class TimeStampedFieldAngularCoordinates<T extends RealFieldElement<T>>
extends FieldAngularCoordinates<T>
implements TimeStamped

time-stamped version of FieldAngularCoordinates.

Instances of this class are guaranteed to be immutable.

Since:

7.0

Author:

Luc Maisonobe

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
TimeStampedFieldAngularCoordinates(AbsoluteDate date, FieldRotation<T> rotation, FieldVector3D<T> rotationRate, FieldVector3D<T> rotationAcceleration) Builds a rotation/rotation rate pair.

Method Summary

Methods

Modifier and Type	Method and Description
TimeStampedFieldAngularCoordinates<T>	addOffset(FieldAngularCoordinates<T> offset) Add an offset from the instance.
AbsoluteDate	getDate() Get the date.
static <T extends RealFieldElement<T>> TimeStampedFieldAngularCoordinates<T>	interpolate(AbsoluteDate date, AngularDerivativesFilter filter, Collection<TimeStampedFieldAngularCoordinates<T>> sample) Interpolate angular coordinates.
TimeStampedFieldAngularCoordinates<T>	revert() Revert a rotation/rotation rate pair.
TimeStampedFieldAngularCoordinates<T>	shiftedBy(double dt) Get a time-shifted state.
TimeStampedFieldAngularCoordinates<T>	subtractOffset(FieldAngularCoordinates<T> offset) Subtract an offset from the instance.

Methods inherited from class org.orekit.utils.FieldAngularCoordinates

estimateRate, getRotation, getRotationAcceleration, getRotationRate, interpolate, toAngularCoordinates

Methods inherited from class java.lang.Object

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

Constructor Detail

TimeStampedFieldAngularCoordinates

public TimeStampedFieldAngularCoordinates(AbsoluteDate date,
                                  FieldRotation<T> rotation,
                                  FieldVector3D<T> rotationRate,
                                  FieldVector3D<T> rotationAcceleration)

Builds a rotation/rotation rate pair.

Parameters:

date - coordinates date

rotation - rotation

rotationRate - FieldRotation rate Ω (rad/s)

rotationAcceleration - FieldRotation acceleration dΩ/dt (rad²/s²)

Method Detail

getDate

public AbsoluteDate getDate()

Get the date.

Specified by:

getDate in interface TimeStamped

Returns:

date attached to the object

revert

public TimeStampedFieldAngularCoordinates<T> revert()

Revert a rotation/rotation rate pair. Build a pair which reverse the effect of another pair.

Overrides:

revert in class FieldAngularCoordinates<T extends RealFieldElement<T>>

Returns:

a new pair whose effect is the reverse of the effect of the instance

shiftedBy

public TimeStampedFieldAngularCoordinates<T> shiftedBy(double dt)

Get a time-shifted state.

The state can be slightly shifted to close dates. This shift is based on a simple linear model. 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<FieldAngularCoordinates<T extends RealFieldElement<T>>>

Overrides:

shiftedBy in class FieldAngularCoordinates<T extends RealFieldElement<T>>

Parameters:

dt - time shift in seconds

Returns:

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

addOffset

public TimeStampedFieldAngularCoordinates<T> addOffset(FieldAngularCoordinates<T> offset)

Add an offset from the instance.

We consider here that the offset FieldRotation is applied first and the instance is applied afterward. Note that angular coordinates do not commute under this operation, i.e. a.addOffset(b) and b.addOffset(a) lead to different results in most cases.

The two methods addOffset and subtractOffset are designed so that round trip applications are possible. This means that both ac1.subtractOffset(ac2).addOffset(ac2) and ac1.addOffset(ac2).subtractOffset(ac2) return angular coordinates equal to ac1.

Overrides:

addOffset in class FieldAngularCoordinates<T extends RealFieldElement<T>>

Parameters:

offset - offset to subtract

Returns:

new instance, with offset subtracted

See Also:

subtractOffset(FieldAngularCoordinates)

subtractOffset

public TimeStampedFieldAngularCoordinates<T> subtractOffset(FieldAngularCoordinates<T> offset)

Subtract an offset from the instance.

We consider here that the offset Rotation is applied first and the instance is applied afterward. Note that angular coordinates do not commute under this operation, i.e. a.subtractOffset(b) and b.subtractOffset(a) lead to different results in most cases.

The two methods addOffset and subtractOffset are designed so that round trip applications are possible. This means that both ac1.subtractOffset(ac2).addOffset(ac2) and ac1.addOffset(ac2).subtractOffset(ac2) return angular coordinates equal to ac1.

Overrides:

subtractOffset in class FieldAngularCoordinates<T extends RealFieldElement<T>>

Parameters:

offset - offset to subtract

Returns:

new instance, with offset subtracted

See Also:

addOffset(FieldAngularCoordinates)

interpolate

public static <T extends RealFieldElement<T>> TimeStampedFieldAngularCoordinates<T> interpolate(AbsoluteDate date,
                                                                                AngularDerivativesFilter filter,
                                                                                Collection<TimeStampedFieldAngularCoordinates<T>> sample)
                                                                                     throws OrekitException

Interpolate angular coordinates.

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

This method is based on Sergei Tanygin's paper Attitude Interpolation, changing the norm of the vector to match the modified Rodrigues vector as described in Malcolm D. Shuster's paper A Survey of Attitude Representations. This change avoids the singularity at π. There is still a singularity at 2π, which is handled by slightly offsetting all FieldRotations when this singularity is detected.

Note that even if first time derivatives (FieldRotation rates) from sample can be ignored, the interpolated instance always includes interpolated derivatives. This feature can be used explicitly to compute these derivatives when it would be too complex to compute them from an analytical formula: just compute a few sample points from the explicit formula and set the derivatives to zero in these sample points, then use interpolation to add derivatives consistent with the FieldRotations.

Type Parameters:

T - the type of the field elements

Parameters:

date - interpolation date

filter - filter for derivatives from the sample to use in interpolation

sample - sample points on which interpolation should be done

Returns:

a new position-velocity, interpolated at specified date

Throws:

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