Package org.orekit.forces

Class HarmonicParametricAcceleration

java.lang.Object

org.orekit.forces.AbstractForceModel

org.orekit.forces.AbstractParametricAcceleration

org.orekit.forces.HarmonicParametricAcceleration

All Implemented Interfaces:

ForceModel

public class HarmonicParametricAcceleration
extends AbstractParametricAcceleration

This class implements a parametric acceleration with harmonic signed amplitude.

Since:

9.0

Author:

Luc Maisonobe

Constructor Summary

Constructors

Constructor	Description
HarmonicParametricAcceleration(org.hipparchus.geometry.euclidean.threed.Vector3D direction, boolean isInertial, String prefix, AbsoluteDate referenceDate, double fundamentalPeriod, int harmonicMultiplier)	Simple constructor.
HarmonicParametricAcceleration(org.hipparchus.geometry.euclidean.threed.Vector3D direction, AttitudeProvider attitudeOverride, String prefix, AbsoluteDate referenceDate, double fundamentalPeriod, int harmonicMultiplier)	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 org.hipparchus.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.AbstractParametricAcceleration

acceleration, acceleration, getEventsDetectors, getFieldEventsDetectors, isInertial

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

Constructor Detail

HarmonicParametricAcceleration

public HarmonicParametricAcceleration(org.hipparchus.geometry.euclidean.threed.Vector3D direction,
                                      boolean isInertial,
                                      String prefix,
                                      AbsoluteDate referenceDate,
                                      double fundamentalPeriod,
                                      int harmonicMultiplier)

Simple constructor.

The signed amplitude of the acceleration is γ sin[2kπ(t-t₀)/T + φ], where γ is parameter 0 and represents the full amplitude, t is current date, t₀ is reference date, T is fundamental period, k is harmonic multiplier, and φ is parameter 1 and represents phase at t₀. The value t-t₀ is in seconds.

The fundamental period T is often set to the Keplerian period of the orbit and the harmonic multiplier k is often set to 1 or 2. The model has two parameters, one for the full amplitude and one for the phase at reference date.

The two parameters for this model are the full amplitude (parameter 0) and the phase at reference date (parameter 1). Their reference values (used also as the initial values) are both 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 phase, if null the reference date will be automatically set at propagation start

fundamentalPeriod - fundamental period (typically set to initial orbit Keplerian period)

harmonicMultiplier - multiplier to compute harmonic period from fundamental period)

HarmonicParametricAcceleration

public HarmonicParametricAcceleration(org.hipparchus.geometry.euclidean.threed.Vector3D direction,
                                      AttitudeProvider attitudeOverride,
                                      String prefix,
                                      AbsoluteDate referenceDate,
                                      double fundamentalPeriod,
                                      int harmonicMultiplier)

Simple constructor.

The signed amplitude of the acceleration is γ sin[2kπ(t-t₀)/T + φ], where γ is parameter 0 and represents the full amplitude, t is current date, t₀ is reference date, T is fundamental period, k is harmonic multiplier, and φ is parameter 1 and represents phase at t₀. The value t-t₀ is in seconds.

The fundamental period T is often set to the Keplerian period of the orbit and the harmonic multiplier k is often set to 1 or 2. The model has two parameters, one for the full amplitude and one for the phase at reference date.

The two parameters for this model are the full amplitude (parameter 0) and the phase at reference date (parameter 1). Their reference values (used also as the initial values) are both 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 phase, if null the reference date will be automatically set at propagation start

fundamentalPeriod - fundamental period (typically set to initial orbit Keplerian period)

harmonicMultiplier - multiplier to compute harmonic period from fundamental period)

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)

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().

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.

. The signed amplitude of the acceleration is γ sin[2kπ(t-t₀)/T + φ], where γ is parameter 0 and represents the full amplitude, t is current date, t₀ is reference date, T is fundamental period, k is harmonic multiplier, and φ is parameter 1 and represents phase at t₀. The value t-t₀ is in seconds.

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 org.hipparchus.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.

The signed amplitude of the acceleration is γ sin[2kπ(t-t₀)/T + φ], where γ is parameter 0 and represents the full amplitude, t is current date, t₀ is reference date, T is fundamental period, k is harmonic multiplier, and φ is parameter 1 and represents phase at t₀. The value t-t₀ is in seconds.

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