Package org.orekit.forces

Class PolynomialParametricAcceleration

java.lang.Object

org.orekit.forces.AbstractForceModel

org.orekit.forces.AbstractParametricAcceleration

org.orekit.forces.PolynomialParametricAcceleration

All Implemented Interfaces:

ForceModel

public class PolynomialParametricAcceleration
extends AbstractParametricAcceleration

This class implements a parametric acceleration with polynomial signed amplitude.

Since:

9.0

Author:

Luc Maisonobe

Constructor Summary

Constructors

Constructor	Description
PolynomialParametricAcceleration(Vector3D direction, boolean isInertial, String prefix, AbsoluteDate referenceDate, int degree)	Simple constructor.
PolynomialParametricAcceleration(Vector3D direction, AttitudeProvider attitudeOverride, String prefix, AbsoluteDate referenceDate, int degree)	Simple constructor.

Method Summary

Modifier and Type	Method	Description
boolean	dependsOnPositionOnly()	Check if force models depends on position only.
ParameterDriver[]	getParametersDrivers()	Get the drivers for force model parameters.
void	init(SpacecraftState initialState, AbsoluteDate target)	Initialize the force model at the start of propagation.
protected <T extends RealFieldElement<T>> T	signedAmplitude(FieldSpacecraftState<T> state, T[] parameters)	Compute the signed amplitude of the acceleration.
protected double	signedAmplitude(SpacecraftState state, double[] parameters)	Compute the signed amplitude of the acceleration.

Methods inherited from class org.orekit.forces.AbstractForceModel

complainIfNotSupported, getParameterDriver, isSupported

Methods inherited from class org.orekit.forces.AbstractParametricAcceleration

acceleration, acceleration, getEventsDetectors, getFieldEventsDetectors, isInertial

Methods inherited from interface org.orekit.forces.ForceModel

addContribution, addContribution, getParameters, getParameters

Methods inherited from class java.lang.Object

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

Constructor Detail

PolynomialParametricAcceleration

public PolynomialParametricAcceleration(Vector3D direction,
                                        boolean isInertial,
                                        String prefix,
                                        AbsoluteDate referenceDate,
                                        int degree)

Simple constructor.

The signed amplitude of the acceleration is ∑pₙ(t-t₀)ⁿ, where pₙ is parameter n, t is current date and t₀ is reference date. The value t-t₀ is in seconds.

The degree + 1 parameters for this model are the polynomial coefficients in increasing degree order. Their reference values (used also as the initial values) are all set to 0. User can change them before starting the propagation (or orbit determination) by calling getParametersDrivers() and ParameterDriver.setValue(double).

Parameters:

direction - acceleration direction in defining 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)

prefix - prefix to use for parameter drivers

referenceDate - reference date for computing polynomials, if null the reference date will be automatically set at propagation start

degree - polynomial degree (i.e. a value of 0 corresponds to a constant acceleration)

PolynomialParametricAcceleration

public PolynomialParametricAcceleration(Vector3D direction,
                                        AttitudeProvider attitudeOverride,
                                        String prefix,
                                        AbsoluteDate referenceDate,
                                        int degree)

Simple constructor.

The signed amplitude of the acceleration is ∑pₙ(t-t₀)ⁿ, where pₙ is parameter n, t is current date and t₀ is reference date. The value t-t₀ is in seconds.

The degree + 1 parameters for this model are the polynomial coefficients in increasing degree order. Their reference values (used also as the initial values) are all set to 0. User can change them before starting the propagation (or orbit determination) by calling getParametersDrivers() and ParameterDriver.setValue(double).

Parameters:

direction - acceleration direction in overridden spacecraft frame

attitudeOverride - provider for attitude used to compute acceleration direction

prefix - prefix to use for parameter drivers

referenceDate - reference date for computing polynomials, if null the reference date will be automatically set at propagation start

degree - polynomial degree (i.e. a value of 0 corresponds to a constant acceleration)

Method Detail

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

init

public void init(SpacecraftState initialState,
                 AbsoluteDate target)
          throws OrekitException

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, RealFieldElement[])

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().

Throws:

OrekitException - if an implementing class overrides the default behavior and takes some action that throws an OrekitException.

signedAmplitude

protected double signedAmplitude(SpacecraftState state,
                                 double[] parameters)

Compute the signed amplitude of the acceleration.

The acceleration is the direction multiplied by the signed amplitude. So if signed amplitude is negative, the acceleratin is towards the opposite of the direction specified at construction.

Specified by:

signedAmplitude in class AbstractParametricAcceleration

Parameters:

state - current state information: date, kinematics, attitude

parameters - values of the force model parameters

Returns:

norm of the acceleration

signedAmplitude

protected <T extends RealFieldElement<T>> T signedAmplitude(FieldSpacecraftState<T> state,
                                                            T[] parameters)

Compute the signed amplitude of the acceleration.

The acceleration is the direction multiplied by the signed amplitude. So if signed amplitude is negative, the acceleratin is towards the opposite of the direction specified at construction.

Specified by:

signedAmplitude in class AbstractParametricAcceleration

Type Parameters:

T - type of the elements

Parameters:

state - current state information: date, kinematics, attitude

parameters - values of the force model parameters

Returns:

norm of the acceleration

getParametersDrivers

public ParameterDriver[] getParametersDrivers()

Get the drivers for force model parameters.

Returns:

drivers for force model parameters