org.orekit.propagation

Class FieldStateCovariance<T extends org.hipparchus.CalculusFieldElement<T>>

java.lang.Object

org.orekit.propagation.FieldStateCovariance<T>

Type Parameters:

T - type of the field elements

All Implemented Interfaces:

FieldTimeStamped<T>

public class FieldStateCovariance<T extends org.hipparchus.CalculusFieldElement<T>>
extends Object
implements FieldTimeStamped<T>

This class is the representation of a covariance matrix at a given date.

Currently, the covariance only represents the orbital elements.

It is possible to change the covariance frame by using the changeCovarianceFrame(FieldOrbit, Frame) or changeCovarianceFrame(FieldOrbit, LOF) method. These methods are based on Equations (18) and (20) of Covariance Transformations for Satellite Flight Dynamics Operations by David A. SVallado.

Finally, covariance orbit type can be changed using the changeCovarianceType(FieldOrbit, OrbitType, PositionAngle) method.

Since:

12.0

Author:

Bryan Cazabonne, Vincent Cucchietti

Constructor Summary

Constructors

Constructor and Description
FieldStateCovariance(org.hipparchus.linear.FieldMatrix<T> orbitalCovariance, FieldAbsoluteDate<T> epoch, Frame covarianceFrame, OrbitType orbitType, PositionAngleType angleType) Constructor.
FieldStateCovariance(org.hipparchus.linear.FieldMatrix<T> orbitalCovariance, FieldAbsoluteDate<T> epoch, LOF lof) Constructor.

Method Summary

Modifier and Type	Method and Description
FieldStateCovariance<T>	changeCovarianceFrame(FieldOrbit<T> orbit, Frame frameOut) Get the covariance in the output frame.
FieldStateCovariance<T>	changeCovarianceFrame(FieldOrbit<T> orbit, LOF lofOut) Get the covariance in a given local orbital frame.
FieldStateCovariance<T>	changeCovarianceType(FieldOrbit<T> orbit, OrbitType outOrbitType, PositionAngleType outAngleType) Get the covariance matrix in another orbit type.
FieldAbsoluteDate<T>	getDate() Get the date.
Frame	getFrame() Get the covariance frame.
LOF	getLOF() Get the covariance LOF type.
org.hipparchus.linear.FieldMatrix<T>	getMatrix() Get the covariance matrix.
OrbitType	getOrbitType() Get the covariance orbit type.
PositionAngleType	getPositionAngleType() Get the covariance angle type.
FieldStateCovariance<T>	shiftedBy(org.hipparchus.Field<T> field, FieldOrbit<T> orbit, T dt) Get a time-shifted covariance matrix.
StateCovariance	toStateCovariance() Get new state covariance instance.

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.FieldTimeStamped

durationFrom

Constructor Detail

FieldStateCovariance

public FieldStateCovariance(org.hipparchus.linear.FieldMatrix<T> orbitalCovariance,
                            FieldAbsoluteDate<T> epoch,
                            LOF lof)

Constructor.

Parameters:

orbitalCovariance - 6x6 orbital parameters covariance

epoch - epoch of the covariance

lof - covariance LOF type

FieldStateCovariance

public FieldStateCovariance(org.hipparchus.linear.FieldMatrix<T> orbitalCovariance,
                            FieldAbsoluteDate<T> epoch,
                            Frame covarianceFrame,
                            OrbitType orbitType,
                            PositionAngleType angleType)

Constructor.

Parameters:

orbitalCovariance - 6x6 orbital parameters covariance

epoch - epoch of the covariance

covarianceFrame - covariance frame (inertial or Earth fixed)

orbitType - orbit type of the covariance (CARTESIAN if covarianceFrame is not pseudo-inertial)

angleType - position angle type of the covariance (not used if orbitType is CARTESIAN)

Method Detail

getDate

public FieldAbsoluteDate<T> getDate()

Get the date..

Specified by:

getDate in interface FieldTimeStamped<T extends org.hipparchus.CalculusFieldElement<T>>

Returns:

date attached to the object

getMatrix

public org.hipparchus.linear.FieldMatrix<T> getMatrix()

Get the covariance matrix.

Returns:

the covariance matrix

getOrbitType

public OrbitType getOrbitType()

Get the covariance orbit type.

Returns:

the covariance orbit type

getPositionAngleType

public PositionAngleType getPositionAngleType()

Get the covariance angle type.

Returns:

the covariance angle type

getFrame

public Frame getFrame()

Get the covariance frame.

Returns:

the covariance frame (can be null)

See Also:

getLOF()

getLOF

public LOF getLOF()

Get the covariance LOF type.

Returns:

the covariance LOF type (can be null)

See Also:

getFrame()

changeCovarianceType

public FieldStateCovariance<T> changeCovarianceType(FieldOrbit<T> orbit,
                                                    OrbitType outOrbitType,
                                                    PositionAngleType outAngleType)

Get the covariance matrix in another orbit type.

The covariance orbit type cannot be changed if the covariance matrix is expressed in a local orbital frame or a non-pseudo inertial frame.

As this type change uses the jacobian matrix of the transformation, it introduces a linear approximation. Hence, the current covariance matrix will not exactly match the new linearized case and the distribution will not follow a generalized Gaussian distribution anymore.

This is based on equation (1) to (6) from "Vallado, D. A. (2004). Covariance transformations for satellite flight dynamics operations."

Parameters:

orbit - orbit to which the covariance matrix should correspond

outOrbitType - target orbit type of the state covariance matrix

outAngleType - target position angle type of the state covariance matrix

Returns:

a new covariance state, expressed in the target orbit type with the target position angle

See Also:

changeCovarianceFrame(FieldOrbit, Frame)

changeCovarianceFrame

public FieldStateCovariance<T> changeCovarianceFrame(FieldOrbit<T> orbit,
                                                     LOF lofOut)

Get the covariance in a given local orbital frame.

Changing the covariance frame is a linear process, this method does not introduce approximation unless a change in covariance orbit type is required.

This is based on equation (18) to (20) "from Vallado, D. A. (2004). Covariance transformations for satellite flight dynamics operations."

Parameters:

orbit - orbit to which the covariance matrix should correspond

lofOut - output local orbital frame

Returns:

a new covariance state, expressed in the output local orbital frame

changeCovarianceFrame

public FieldStateCovariance<T> changeCovarianceFrame(FieldOrbit<T> orbit,
                                                     Frame frameOut)

Get the covariance in the output frame.

Changing the covariance frame is a linear process, this method does not introduce approximation unless a change in covariance orbit type is required.

This is based on equation (18) to (20) "from Vallado, D. A. (2004). Covariance transformations for satellite flight dynamics operations."

Parameters:

orbit - orbit to which the covariance matrix should correspond

frameOut - output frame

Returns:

a new covariance state, expressed in the output frame

shiftedBy

public FieldStateCovariance<T> shiftedBy(org.hipparchus.Field<T> field,
                                         FieldOrbit<T> orbit,
                                         T dt)

Get a time-shifted covariance matrix.

The shifting model is a linearized, Keplerian one. In other words, it is based on a state transition matrix that is computed assuming Keplerian motion.

Shifting is not intended as a replacement for proper covariance propagation, but should be sufficient for small time shifts or coarse accuracy.

Parameters:

field - to which the elements belong

orbit - orbit to which the covariance matrix should correspond

dt - time shift in seconds

Returns:

a new covariance state, shifted with respect to the instance

toStateCovariance

public StateCovariance toStateCovariance()

Get new state covariance instance.

Returns:

new state covariance instance.