Package org.orekit.forces.empirical

Class ParametricAcceleration

java.lang.Object

org.orekit.forces.empirical.ParametricAcceleration

All Implemented Interfaces:

ForceModel, EventDetectorsProvider, ParameterDriversProvider

public class ParametricAcceleration
extends Object
implements ForceModel

This class implements a parametric acceleration.

Parametric accelerations are intended to model lesser-known forces, estimating a few defining parameters from a parametric function using orbit determination. Typical parametric functions are polynomial (often limited to a constant term) and harmonic (often with either orbital period or half orbital period).

An important operational example is the infamous GPS Y-bias, which is thought to be related to a radiator thermal radiation. Other examples could be to model leaks that produce roughly constant trust in some spacecraft-related direction.

The acceleration direction is considered constant in either:

• inertial frame
• spacecraft frame
• a dedicated attitude frame overriding spacecraft attitude (this could for example be used to model solar arrays orientation if the force is related to solar arrays)

If the direction of the acceleration is unknown, then three instances of this class should be used, one along the X axis, one along the Y axis and one along the Z axis and their parameters estimated as usual.

Since:

10.3

Author:

Luc Maisonobe, Bryan Cazabonne, Melina Vanel

Field Summary

Fields inherited from interface org.orekit.propagation.events.EventDetectorsProvider

DATATION_ACCURACY

Constructor Summary

Constructors

Constructor	Description
ParametricAcceleration(Vector3D direction, boolean isInertial, AccelerationModel accelerationModel)	Simple constructor.
ParametricAcceleration(Vector3D direction, AttitudeProvider attitudeOverride, AccelerationModel accelerationModel)	Simple constructor.

Method Summary

Modifier and Type	Method	Description
<T extends CalculusFieldElement<T>> FieldVector3D<T>	acceleration(FieldSpacecraftState<T> state, T[] parameters)	Compute acceleration.
Vector3D	acceleration(SpacecraftState state, double[] parameters)	Compute acceleration.
boolean	dependsOnPositionOnly()	Check if force model depends on position only at a given, fixed date.
Stream<EventDetector>	getEventDetectors()	Get the discrete events related to the model.
<T extends CalculusFieldElement<T>> Stream<FieldEventDetector<T>>	getFieldEventDetectors(Field<T> field)	Get the discrete events related to the model.
List<ParameterDriver>	getParametersDrivers()	Get the drivers for parameters.
void	init(SpacecraftState initialState, AbsoluteDate target)	Initialize the force model at the start of propagation.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.orekit.propagation.events.EventDetectorsProvider

getEventDetectors, getFieldEventDetectors

Methods inherited from interface org.orekit.forces.ForceModel

addContribution, addContribution, dependsOnAttitudeRate, init

Methods inherited from interface org.orekit.utils.ParameterDriversProvider

getNbParametersDriversValue, getParameterDriver, getParameters, getParameters, getParameters, getParameters, getParametersAllValues, getParametersAllValues, isSupported

Constructor Detail

ParametricAcceleration

public ParametricAcceleration(Vector3D direction,
                              boolean isInertial,
                              AccelerationModel accelerationModel)

Simple constructor.

Parameters:

direction - acceleration direction in overridden spacecraft frame

isInertial - if true, direction is defined in the same inertial frame used for propagation (i.e. SpacecraftState.getFrame()), otherwise direction is defined in spacecraft frame (i.e. using the propagation attitude law)

accelerationModel - acceleration model used to compute the contribution of the empirical acceleration direction

ParametricAcceleration

public ParametricAcceleration(Vector3D direction,
                              AttitudeProvider attitudeOverride,
                              AccelerationModel accelerationModel)

Simple constructor.

Parameters:

direction - acceleration direction in overridden spacecraft frame frame used for propagation (i.e. SpacecraftState.getFrame()), otherwise direction is defined in spacecraft frame (i.e. using the propagation attitude law)

attitudeOverride - provider for attitude used to compute acceleration

accelerationModel - acceleration model used to compute the contribution of the empirical acceleration direction

Method Detail

dependsOnPositionOnly

public boolean dependsOnPositionOnly()

Check if force model depends on position only at a given, fixed date.

Specified by:

dependsOnPositionOnly in interface ForceModel

Returns:

true if force model depends on position only, false if it depends on velocity, either directly or due to a dependency on attitude

getParametersDrivers

public List<ParameterDriver> getParametersDrivers()

Get the drivers for parameters.

Specified by:

getParametersDrivers in interface ParameterDriversProvider

Returns:

drivers for parameters

init

public void init(SpacecraftState initialState,
                 AbsoluteDate target)

Initialize the force model at the start of propagation. This method will be called before any calls to ForceModel.addContribution(SpacecraftState, TimeDerivativesEquations), ForceModel.addContribution(FieldSpacecraftState, FieldTimeDerivativesEquations), ForceModel.acceleration(SpacecraftState, double[]) or ForceModel.acceleration(FieldSpacecraftState, CalculusFieldElement[])

The default implementation of this method does nothing.

Specified by:

init in interface ForceModel

Parameters:

initialState - spacecraft state at the start of propagation.

target - date of propagation. Not equal to initialState.getDate().

acceleration

public Vector3D acceleration(SpacecraftState state,
                             double[] parameters)

Compute acceleration.

Specified by:

acceleration in interface ForceModel

Parameters:

state - current state information: date, kinematics, attitude

parameters - values of the force model parameters at state date, only 1 value for each parameterDriver

Returns:

acceleration in same frame as state

acceleration

public <T extends CalculusFieldElement<T>> FieldVector3D<T> acceleration(FieldSpacecraftState<T> state,
                                                                         T[] parameters)

Compute acceleration.

Specified by:

acceleration in interface ForceModel

Type Parameters:

T - type of the elements

Parameters:

state - current state information: date, kinematics, attitude

parameters - values of the force model parameters at state date, only 1 value for each parameterDriver

Returns:

acceleration in same frame as state

getEventDetectors

public Stream<EventDetector> getEventDetectors()

Get the discrete events related to the model.

This method is not intended to be called several time, only once by a propagator, as it has the side effect of rebuilding the events detectors when called.

Specified by:

getEventDetectors in interface EventDetectorsProvider

Specified by:

getEventDetectors in interface ForceModel

Returns:

stream of event detectors

getFieldEventDetectors

public <T extends CalculusFieldElement<T>> Stream<FieldEventDetector<T>> getFieldEventDetectors(Field<T> field)

Get the discrete events related to the model.

This method is not intended to be called several time, only once by a propagator, as it has the side effect of rebuilding the events detectors when called.

Specified by:

getFieldEventDetectors in interface EventDetectorsProvider

Specified by:

getFieldEventDetectors in interface ForceModel

Type Parameters:

T - extends CalculusFieldElement<T>

Parameters:

field - field to which the state belongs

Returns:

stream of event detectors