org.orekit.forces

Class AbstractParametricAcceleration

java.lang.Object

org.orekit.forces.AbstractForceModel

org.orekit.forces.AbstractParametricAcceleration

All Implemented Interfaces:

ForceModel

Direct Known Subclasses:

HarmonicParametricAcceleration, PolynomialParametricAcceleration

public abstract class AbstractParametricAcceleration
extends AbstractForceModel

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:

9.0

Author:

Luc Maisonobe

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractParametricAcceleration(org.hipparchus.geometry.euclidean.threed.Vector3D direction, boolean isInertial, AttitudeProvider attitudeOverride) Simple constructor.

Method Summary

Modifier and Type	Method and Description
<T extends org.hipparchus.RealFieldElement<T>> org.hipparchus.geometry.euclidean.threed.FieldVector3D<T>	acceleration(FieldSpacecraftState<T> state, T[] parameters) Compute acceleration.
org.hipparchus.geometry.euclidean.threed.Vector3D	acceleration(SpacecraftState state, double[] parameters) Compute acceleration.
Stream<EventDetector>	getEventsDetectors() Get the discrete events related to the model.
<T extends org.hipparchus.RealFieldElement<T>> Stream<FieldEventDetector<T>>	getFieldEventsDetectors(org.hipparchus.Field<T> field) Get the discrete events related to the model.
protected boolean	isInertial() Check if direction is inertial.
protected abstract <T extends org.hipparchus.RealFieldElement<T>> T	signedAmplitude(FieldSpacecraftState<T> state, T[] parameters) Compute the signed amplitude of the acceleration.
protected abstract 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 java.lang.Object

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

Methods inherited from interface org.orekit.forces.ForceModel

addContribution, addContribution, dependsOnPositionOnly, getParameters, getParameters, getParametersDrivers, init

Constructor Detail

AbstractParametricAcceleration

protected AbstractParametricAcceleration(org.hipparchus.geometry.euclidean.threed.Vector3D direction,
                                         boolean isInertial,
                                         AttitudeProvider attitudeOverride)

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)

attitudeOverride - provider for attitude used to compute acceleration direction

Method Detail

isInertial

protected boolean isInertial()

Check if direction is inertial.

Returns:

true if direction is inertial

signedAmplitude

protected abstract 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.

Parameters:

state - current state information: date, kinematics, attitude

parameters - values of the force model parameters

Returns:

norm of the acceleration

signedAmplitude

protected abstract <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.

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

acceleration

public org.hipparchus.geometry.euclidean.threed.Vector3D acceleration(SpacecraftState state,
                                                                      double[] parameters)
                                                               throws OrekitException

Compute acceleration.

Parameters:

state - current state information: date, kinematics, attitude

parameters - values of the force model parameters

Returns:

acceleration in same frame as state

Throws:

OrekitException - if some specific error occurs

acceleration

public <T extends org.hipparchus.RealFieldElement<T>> org.hipparchus.geometry.euclidean.threed.FieldVector3D<T> acceleration(FieldSpacecraftState<T> state,
                                                                                                                             T[] parameters)
                                                                                                                      throws OrekitException

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

Throws:

OrekitException - if some specific error occurs

getEventsDetectors

public Stream<EventDetector> getEventsDetectors()

Get the discrete events related to the model.

Returns:

stream of events detectors

getFieldEventsDetectors

public <T extends org.hipparchus.RealFieldElement<T>> Stream<FieldEventDetector<T>> getFieldEventsDetectors(org.hipparchus.Field<T> field)

Get the discrete events related to the model.

Type Parameters:

T - extends RealFieldElement

Parameters:

field - field to which the state belongs

Returns:

stream of events detectors