org.orekit.forces.empirical

Class TimeSpanParametricAcceleration

java.lang.Object

org.orekit.forces.AbstractForceModel

org.orekit.forces.empirical.TimeSpanParametricAcceleration

All Implemented Interfaces:

ForceModel

public class TimeSpanParametricAcceleration
extends AbstractForceModel

Time span parametric acceleration model.

This class is closely related to ParametricAcceleration class.
The difference is that it has a TimeSpanMap of AccelerationModel objects as attribute instead of a single AccelerationModel object.
The idea behind this model is to allow the user to design a parametric acceleration model that can see its physical parameters change with time, at dates chosen by the user.

This is a behavior that can be sought in precise orbit determination.
Indeed for this type of application, the empirical parameters must be revalued at each new orbit.

Usage:

• Construction: constructor takes an acceleration direction, an attitude mode (or an inertial flag) and an AccelerationModel model.
  This last model will be your initial AccelerationModel model and it will be initially valid for the whole time line.
  The real validity of this first entry will be truncated as other AccelerationModel models are added.
• Time spans: AccelerationModel models are added using methods addAccelerationModelValidAfter(AccelerationModel, AbsoluteDate) or addAccelerationModelValidBefore(AccelerationModel, AbsoluteDate).
  Recommendations are the same than the ones in TimeSpanMap, meaning:
  • As an entry is added, it truncates the validity of the neighboring entries already present in the map;
  • The transition dates should be entered only once. Repeating a transition date will lead to unexpected result and is not supported;
  • It is advised to order your AccelerationModel models chronologically when adding them to avoid any confusion.
• Naming the parameter drivers: It is strongly advised to give a custom name to the ParameterDriver(s) of each AccelerationModel model that is added to the object. This will allow you keeping track of the evolution of your models.
  Different names are mandatory to differentiate the different drivers.
  Since there is no default name for acceleration model parameters, you must handle the driver names to consider different names when adding a new acceleration model.

Since:

10.3

Author:

Bryan Cazabonne

Field Summary

Fields

Modifier and Type	Field and Description
static String	DATE_AFTER Prefix for dates after in the parameter drivers' name.
static String	DATE_BEFORE Prefix for dates before in the parameter drivers' name.

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
<T extends CalculusFieldElement<T>> FieldVector3D<T>	acceleration(FieldSpacecraftState<T> state, T[] parameters) Compute acceleration.
Vector3D	acceleration(SpacecraftState state, double[] parameters) Compute acceleration.
void	addAccelerationModelValidAfter(AccelerationModel accelerationModel, AbsoluteDate earliestValidityDate) Add a AccelerationModel entry valid after a limit date.
void	addAccelerationModelValidBefore(AccelerationModel accelerationModel, AbsoluteDate latestValidityDate) Add an AccelerationModel entry valid before a limit date.
boolean	dependsOnPositionOnly() Check if force models depends on position only.
TimeSpanMap<AccelerationModel>	extractAccelerationModelRange(AbsoluteDate start, AbsoluteDate end) Extract a range of the AccelerationModel map.
double[]	extractParameters(double[] parameters, AbsoluteDate date) Extract the proper parameter drivers' values from the array in input of the acceleration method.
<T extends CalculusFieldElement<T>> T[]	extractParameters(T[] parameters, FieldAbsoluteDate<T> date) Extract the proper parameter drivers' values from the array in input of the acceleration method.
AccelerationModel	getAccelerationModel(AbsoluteDate date) Get the AccelerationModel model valid at a date.
TimeSpanMap.Span<AccelerationModel>	getAccelerationModelSpan(AbsoluteDate date) Get the AccelerationModel TimeSpanMap.Span containing a specified date.
Stream<EventDetector>	getEventsDetectors() Get the discrete events related to the model.
<T extends CalculusFieldElement<T>> Stream<FieldEventDetector<T>>	getFieldEventsDetectors(Field<T> field) Get the discrete events related to the model.
List<ParameterDriver>	getParametersDrivers() Get the drivers for force model parameters.
NavigableSet<TimeSpanMap.Transition<AccelerationModel>>	getTransitions() Get the TimeSpanMap.Transitions of the acceleration model time span map.
void	init(SpacecraftState initialState, AbsoluteDate target) Initialize the force model at the start of propagation.

Methods inherited from class org.orekit.forces.AbstractForceModel

complainIfNotSupported, getParameterDriver, isSupported

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.orekit.forces.ForceModel

addContribution, addContribution, getParameters, getParameters

Field Detail

DATE_BEFORE

public static final String DATE_BEFORE

Prefix for dates before in the parameter drivers' name.

See Also:

Constant Field Values

DATE_AFTER

public static final String DATE_AFTER

Prefix for dates after in the parameter drivers' name.

See Also:

Constant Field Values

Constructor Detail

TimeSpanParametricAcceleration

public TimeSpanParametricAcceleration(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

TimeSpanParametricAcceleration

public TimeSpanParametricAcceleration(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

Method Detail

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.

Parameters:

initialState - spacecraft state at the start of propagation.

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

addAccelerationModelValidBefore

public void addAccelerationModelValidBefore(AccelerationModel accelerationModel,
                                            AbsoluteDate latestValidityDate)

Add an AccelerationModel entry valid before a limit date.

Using addAccelerationModelValidBefore(entry, t) will make entry valid in ]-∞, t[ (note the open bracket).

WARNING: Since there is no default name for acceleration model parameters, the user must handle itself the driver names to consider different names (i.e. different parameters) when adding a new acceleration model.

Parameters:

accelerationModel - AccelerationModel entry

latestValidityDate - date before which the entry is valid (must be different from all dates already used for transitions)

addAccelerationModelValidAfter

public void addAccelerationModelValidAfter(AccelerationModel accelerationModel,
                                           AbsoluteDate earliestValidityDate)

Add a AccelerationModel entry valid after a limit date.

Using addAccelerationModelValidAfter(entry, t) will make entry valid in [t, +∞[ (note the closed bracket).

WARNING: Since there is no default name for acceleration model parameters, the user must handle itself the driver names to consider different names (i.e. different parameters) when adding a new acceleration model.

Parameters:

accelerationModel - AccelerationModel entry

earliestValidityDate - date after which the entry is valid (must be different from all dates already used for transitions)

getAccelerationModel

public AccelerationModel getAccelerationModel(AbsoluteDate date)

Get the AccelerationModel model valid at a date.

Parameters:

date - the date of validity

Returns:

the AccelerationModel model valid at date

getAccelerationModelSpan

public TimeSpanMap.Span<AccelerationModel> getAccelerationModelSpan(AbsoluteDate date)

Get the AccelerationModel TimeSpanMap.Span containing a specified date.

Parameters:

date - date belonging to the desired time span

Returns:

the AccelerationModel time span containing the specified date

extractAccelerationModelRange

public TimeSpanMap<AccelerationModel> extractAccelerationModelRange(AbsoluteDate start,
                                                                    AbsoluteDate end)

Extract a range of the AccelerationModel map.

The object returned will be a new independent instance that will contain only the transitions that lie in the specified range.

See the TimeSpanMap.extractRange method for more.

Parameters:

start - earliest date at which a transition is included in the range (may be set to AbsoluteDate.PAST_INFINITY to keep all early transitions)

end - latest date at which a transition is included in the r (may be set to AbsoluteDate.FUTURE_INFINITY to keep all late transitions)

Returns:

a new TimeSpanMap instance of AccelerationModel with all transitions restricted to the specified range

getTransitions

public NavigableSet<TimeSpanMap.Transition<AccelerationModel>> getTransitions()

Get the TimeSpanMap.Transitions of the acceleration model time span map.

Returns:

the TimeSpanMap.Transitions for the acceleration model time span map

dependsOnPositionOnly

public boolean dependsOnPositionOnly()

Check if force models depends on position only.

Returns:

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

acceleration

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

Compute acceleration.

Parameters:

state - current state information: date, kinematics, attitude

parameters - values of the force model parameters

Returns:

acceleration in same frame as state

acceleration

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

Compute acceleration.

Type Parameters:

T - type of the elements

Parameters:

state - current state information: date, kinematics, attitude

parameters - values of the force model parameters

Returns:

acceleration in same frame as state

getEventsDetectors

public Stream<EventDetector> getEventsDetectors()

Get the discrete events related to the model.

Returns:

stream of events detectors

getFieldEventsDetectors

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

Get the discrete events related to the model.

Type Parameters:

T - extends CalculusFieldElement<T>

Parameters:

field - field to which the state belongs

Returns:

stream of events detectors

getParametersDrivers

public List<ParameterDriver> getParametersDrivers()

Get the drivers for force model parameters.

All the parameter drivers of all AccelerationModel models are returned in an array. Models are ordered chronologically.

Returns:

drivers for force model parameters

extractParameters

public double[] extractParameters(double[] parameters,
                                  AbsoluteDate date)

Extract the proper parameter drivers' values from the array in input of the acceleration method. Parameters are filtered given an input date.

Parameters:

parameters - the input parameters array

date - the date

Returns:

the parameters given the date

extractParameters

public <T extends CalculusFieldElement<T>> T[] extractParameters(T[] parameters,
                                                                 FieldAbsoluteDate<T> date)

Extract the proper parameter drivers' values from the array in input of the acceleration method. Parameters are filtered given an input date.

Type Parameters:

T - extends CalculusFieldElement

Parameters:

parameters - the input parameters array

date - the date

Returns:

the parameters given the date