public class J2Propagator extends CartesianOnePointPropagator
The following example shows how to create a J2Propagator using the EGM96 gravitational model:
GregorianDate orbitEpoch = new GregorianDate(2007, 5, 30, 12, 0, 0.0);
JulianDate orbitEpochJD = new JulianDate(orbitEpoch);
Motion1<Cartesian> elementsAtEpoch = new Motion1<>(
new Cartesian(12000000.0, 0.0, 0.0), // initial position
new Cartesian(0.0, 5763.0, 0.0)); // initial velocity
J2Propagator propagator = new J2Propagator(
orbitEpochJD,
CentralBodiesFacet.getFromContext().getEarth().getInertialFrame(),
elementsAtEpoch,
EarthGravitationalModel1996.GravitationalParameter,
EarthGravitationalModel1996.J2UnnormalizedValue,
EarthGravitationalModel1996.SemimajorAxis);The analytical model reverts to two-body motion if any portion of the orbit falls within the reference distance specified for the gravity model.
| Modifier | Constructor and Description |
|---|---|
protected |
J2Propagator(J2Propagator existingInstance,
CopyContext context)
Initializes a new instance as a copy of an existing instance.
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|
J2Propagator(JulianDate orbitEpoch,
ReferenceFrame referenceFrame,
DelaunayElements initialConditions,
double j2UnnormalizedValue,
double referenceDistance)
Initializes a new instance.
|
|
J2Propagator(JulianDate orbitEpoch,
ReferenceFrame referenceFrame,
EquinoctialElements initialConditions,
double j2UnnormalizedValue,
double referenceDistance)
Initializes a new instance.
|
|
J2Propagator(JulianDate orbitEpoch,
ReferenceFrame referenceFrame,
KeplerianElements initialConditions,
double j2UnnormalizedValue,
double referenceDistance)
Initializes a new instance.
|
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J2Propagator(JulianDate orbitEpoch,
ReferenceFrame referenceFrame,
ModifiedKeplerianElements initialConditions,
double j2UnnormalizedValue,
double referenceDistance)
Initializes a new instance.
|
|
J2Propagator(JulianDate orbitEpoch,
ReferenceFrame referenceFrame,
Motion1<Cartesian> initialConditions,
double gravitationalParameter,
double j2UnnormalizedValue,
double referenceDistance)
Initializes a new instance.
|
| Modifier and Type | Method and Description |
|---|---|
protected boolean |
checkForSameDefinition(CartesianOnePointPropagator other)
Checks to determine if another instance has the same definition as this instance and
returns
true if it does. |
protected boolean |
checkForSameDefinition(J2Propagator other)
Checks to determine if another instance has the same definition as this instance and
returns
true if it does. |
Object |
clone(CopyContext context)
Clones this object using the specified context.
|
protected int |
computeCurrentDefinitionHashCode()
Computes a hash code based on the current properties of this object.
|
void |
enumerateDependencies(DependencyEnumerator enumerator)
Enumerates the dependencies of this object by calling
DependencyEnumerator#enumerate(T) for each object that this object directly depends upon. |
MotionEvaluator1<Cartesian> |
getEvaluator(EvaluatorGroup group)
Gets an evaluator that can propagate at individual dates.
|
double |
getGravitationalParameter()
Gets the gravitational parameter of the central body around which to propagate.
|
ModifiedKeplerianElements |
getInitialConditions()
Gets the orbital elements from which to propagate.
|
double |
getJ2ZonalHarmonicCoefficient()
Gets the non-normalized J2 zonal harmonic coefficient of the central body around which to propagate.
|
protected ReferenceFrame |
getMotionReferenceFrame()
Gets the reference frame in which the motion is defined.
|
JulianDate |
getOrbitEpoch()
|
double |
getReferenceDistance()
Gets the reference distance (equatorial radius) associated with the J2 coefficient.
|
ReferenceFrame |
getReferenceFrame()
Gets the reference frame in which the ephemeris is produced.
|
void |
setGravitationalParameter(double value)
Sets the gravitational parameter of the central body around which to propagate.
|
void |
setInitialConditions(ModifiedKeplerianElements value)
Sets the orbital elements from which to propagate.
|
void |
setJ2ZonalHarmonicCoefficient(double value)
Sets the non-normalized J2 zonal harmonic coefficient of the central body around which to propagate.
|
void |
setOrbitEpoch(JulianDate value)
|
void |
setReferenceDistance(double value)
Sets the reference distance (equatorial radius) associated with the J2 coefficient.
|
void |
setReferenceFrame(ReferenceFrame value)
Sets the reference frame in which the ephemeris is produced.
|
checkForSameDefinition, createPoint, getEvaluator, propagate, propagateareSameDefinition, areSameDefinition, areSameDefinition, areSameDefinition, areSameDefinition, collectionItemsAreSameDefinition, collectionItemsAreSameDefinition, collectionItemsAreSameDefinition, dictionaryItemsAreSameDefinition, freeze, freezeAggregatedObjects, getCollectionHashCode, getCollectionHashCode, getCollectionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDefinitionHashCode, getDictionaryHashCode, getIsFrozen, isSameDefinition, throwIfFrozenpublic J2Propagator(@Nonnull JulianDate orbitEpoch, @Nonnull ReferenceFrame referenceFrame, @Nonnull Motion1<Cartesian> initialConditions, double gravitationalParameter, double j2UnnormalizedValue, double referenceDistance)
For correct results, referenceFrame generally must be an inertial reference frame. However, it is
easy to obtain ephemeris in any desired ReferenceFrame (get / set) (such as the FixedFrame (get / set)) by
transforming it after it has been produced by the propagator. To do so, call
CartesianOnePointPropagator.propagate(JulianDate,JulianDate,Duration,int,agi.foundation.geometry.ReferenceFrame). Or, call
CartesianOnePointPropagator.createPoint() and then use GeometryTransformer.observePoint(Point,agi.foundation.geometry.ReferenceFrame)
to get an evaluator that can be used to find the propagated position in the specified reference frame.
orbitEpoch - The Julian date at which the initial conditions are defined.referenceFrame - The reference frame in which the initialConditions are defined.
Generally this should be the InertialFrame (get / set) of the central body
around which you are propagating. See the Remarks section for more information.initialConditions - The orbital elements from which to propagate.gravitationalParameter - The gravitational parameter used to propagate.j2UnnormalizedValue - The non-normalized J2 zonal harmonic coefficient of the central body around which to propagate.referenceDistance - The reference distance (equatorial radius) associated with the J2 and J4 coefficients.ArgumentNullException - Thrown if referenceFrame is null.ArgumentException - Thrown if the initialConditions
represent an open orbit (i.e. if the velocity is sufficient to escape the central body).public J2Propagator(@Nonnull JulianDate orbitEpoch, @Nonnull ReferenceFrame referenceFrame, @Nonnull ModifiedKeplerianElements initialConditions, double j2UnnormalizedValue, double referenceDistance)
For correct results, referenceFrame generally must be an inertial reference frame. However, it is
easy to obtain ephemeris in any desired ReferenceFrame (get / set) (such as the FixedFrame (get / set)) by
transforming it after it has been produced by the propagator. To do so, call
CartesianOnePointPropagator.propagate(JulianDate,JulianDate,Duration,int,agi.foundation.geometry.ReferenceFrame). Or, call
CartesianOnePointPropagator.createPoint() and then use GeometryTransformer.observePoint(Point,agi.foundation.geometry.ReferenceFrame)
to get an evaluator that can be used to find the propagated position in the specified reference frame.
orbitEpoch - The Julian date at which the initial conditions are defined.referenceFrame - The reference frame in which the initialConditions are defined.
Generally this should be the InertialFrame (get / set) of the central body
around which you are propagating. See the Remarks section for more information.initialConditions - The orbital elements from which to propagate.j2UnnormalizedValue - The non-normalized J2 zonal harmonic coefficient of the central body around which to propagate.referenceDistance - The reference distance (equatorial radius) associated with the J2 coefficient.ArgumentNullException - Thrown if referenceFrame or initialConditions is null.ArgumentException - Thrown if the initialConditions
represent an open orbit (i.e. if the eccentricity is greater than or equal to unity).public J2Propagator(@Nonnull JulianDate orbitEpoch, @Nonnull ReferenceFrame referenceFrame, @Nonnull KeplerianElements initialConditions, double j2UnnormalizedValue, double referenceDistance)
For correct results, referenceFrame generally must be an inertial reference frame. However, it is
easy to obtain ephemeris in any desired ReferenceFrame (get / set) (such as the FixedFrame (get / set)) by
transforming it after it has been produced by the propagator. To do so, call
CartesianOnePointPropagator.propagate(JulianDate,JulianDate,Duration,int,agi.foundation.geometry.ReferenceFrame). Or, call
CartesianOnePointPropagator.createPoint() and then use GeometryTransformer.observePoint(Point,agi.foundation.geometry.ReferenceFrame)
to get an evaluator that can be used to find the propagated position in the specified reference frame.
orbitEpoch - The Julian date at which the initial conditions are defined.referenceFrame - The reference frame in which the initialConditions are defined.
Generally this should be the InertialFrame (get / set) of the central body
around which you are propagating. See the Remarks section for more information.initialConditions - The orbital elements from which to propagate.j2UnnormalizedValue - The non-normalized J2 zonal harmonic coefficient of the central body around which to propagate.referenceDistance - The reference distance (equatorial radius) associated with the J2 coefficient.ArgumentNullException - Thrown if referenceFrame or initialConditions is null.public J2Propagator(@Nonnull JulianDate orbitEpoch, @Nonnull ReferenceFrame referenceFrame, @Nonnull EquinoctialElements initialConditions, double j2UnnormalizedValue, double referenceDistance)
For correct results, referenceFrame generally must be an inertial reference frame. However, it is
easy to obtain ephemeris in any desired ReferenceFrame (get / set) (such as the FixedFrame (get / set)) by
transforming it after it has been produced by the propagator. To do so, call
CartesianOnePointPropagator.propagate(JulianDate,JulianDate,Duration,int,agi.foundation.geometry.ReferenceFrame). Or, call
CartesianOnePointPropagator.createPoint() and then use GeometryTransformer.observePoint(Point,agi.foundation.geometry.ReferenceFrame)
to get an evaluator that can be used to find the propagated position in the specified reference frame.
orbitEpoch - The Julian date at which the initial conditions are defined.referenceFrame - The reference frame in which the initialConditions are defined.
Generally this should be the InertialFrame (get / set) of the central body
around which you are propagating. See the Remarks section for more information.initialConditions - The orbital elements from which to propagate.j2UnnormalizedValue - The non-normalized J2 zonal harmonic coefficient of the central body around which to propagate.referenceDistance - The reference distance (equatorial radius) associated with the J2 coefficient.ArgumentNullException - Thrown if referenceFrame or initialConditions is null.public J2Propagator(@Nonnull JulianDate orbitEpoch, @Nonnull ReferenceFrame referenceFrame, @Nonnull DelaunayElements initialConditions, double j2UnnormalizedValue, double referenceDistance)
For correct results, referenceFrame generally must be an inertial reference frame. However, it is
easy to obtain ephemeris in any desired ReferenceFrame (get / set) (such as the FixedFrame (get / set)) by
transforming it after it has been produced by the propagator. To do so, call
CartesianOnePointPropagator.propagate(JulianDate,JulianDate,Duration,int,agi.foundation.geometry.ReferenceFrame). Or, call
CartesianOnePointPropagator.createPoint() and then use GeometryTransformer.observePoint(Point,agi.foundation.geometry.ReferenceFrame)
to get an evaluator that can be used to find the propagated position in the specified reference frame.
orbitEpoch - The Julian date at which the initial conditions are defined.referenceFrame - The reference frame in which the initialConditions are defined.
Generally this should be the InertialFrame (get / set) of the central body
around which you are propagating. See the Remarks section for more information.initialConditions - The orbital elements from which to propagate.j2UnnormalizedValue - The non-normalized J2 zonal harmonic coefficient of the central body around which to propagate.referenceDistance - The reference distance (equatorial radius) associated with the J2 coefficient.ArgumentNullException - Thrown if referenceFrame or initialConditions is null.protected J2Propagator(@Nonnull J2Propagator existingInstance, @Nonnull CopyContext context)
See ICloneWithContext.clone(CopyContext) for more information about how to implement this constructor
in a derived class.
existingInstance - The existing instance to copy.context - A CopyContext that controls the depth of the copy.ArgumentNullException - Thrown when existingInstance or context is null.public Object clone(CopyContext context)
This method should be implemented to call a copy constructor on the class of the
object being cloned. The copy constructor should take the CopyContext as a parameter
in addition to the existing instance to copy. The copy constructor should first call
CopyContext.addObjectMapping(T, T) to identify the newly constructed instance
as a copy of the existing instance. It should then copy all fields, using
CopyContext.updateReference(T) to copy any reference fields.
A typical implementation of ICloneWithContext:
public static class MyClass implements ICloneWithContext {
public MyClass(MyClass existingInstance, CopyContext context) {
context.addObjectMapping(existingInstance, this);
someReference = context.updateReference(existingInstance.someReference);
}
@Override
public final Object clone(CopyContext context) {
return new MyClass(this, context);
}
private Object someReference;
}
In general, all fields that are reference types should be copied with a call to
CopyContext.updateReference(T). There are a couple of exceptions:
If one of these exceptions applies, the CopyContext should be given an opportunity
to update the reference before the reference is copied explicitly. Use
CopyContext.updateReference(T) to update the reference. If CopyContext.updateReference(T) returns
the original object, indicating that the context does not have a replacement registered,
then copy the object manually by invoking a Clone method, a copy constructor, or by manually
constructing a new instance and copying the values.
alwaysCopy = context.updateReference(existingInstance.alwaysCopy);
if (existingInstance.alwaysCopy != null && alwaysCopy == existingInstance.alwaysCopy) {
alwaysCopy = (AlwaysCopy) existingInstance.alwaysCopy.clone(context);
}
If you are implementing an evaluator (a class that implements IEvaluator), the
IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) method shares some responsibilities with the
copy context constructor. Code duplication can be avoided by doing the following:
CopyContext.updateReference(T). You should still call CopyContext.updateReference(T) on any references to
non-evaluators.
IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) as the last line in the constructor and pass it the
same CopyContext passed to the constructor.
IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) as normal. See the reference documentation for
IEvaluator.updateEvaluatorReferences(agi.foundation.infrastructure.CopyContext) for more information on implementing that method.
public MyClass(MyClass existingInstance, CopyContext context) {
super(existingInstance, context);
someReference = context.updateReference(existingInstance.someReference);
evaluatorReference = existingInstance.evaluatorReference;
updateEvaluatorReferences(context);
}
@Override
public void updateEvaluatorReferences(CopyContext context) {
evaluatorReference = context.updateReference(evaluatorReference);
}
@Override
public Object clone(CopyContext context) {
return new MyClass(this, context);
}
private Object someReference;
private IEvaluator evaluatorReference;clone in interface ICloneWithContextclone in class DefinitionalObjectcontext - The context to use to perform the copy.protected final boolean checkForSameDefinition(CartesianOnePointPropagator other)
true if it does. Derived classes MUST override this method and check
all new fields introduced by the derived class for definitional equivalence. It is NOT necessary
to check base class fields because the base class will already have done that. When overriding this method,
you should NOT call the base implementation because it will return false for all derived-class instances.
Derived classes should check the type of other to preserve the symmetric nature of IEquatableDefinition.isSameDefinition(java.lang.Object).checkForSameDefinition in class CartesianOnePointPropagatorother - The other instance to compare to this one.true if the two objects are defined equivalently; otherwise false.protected boolean checkForSameDefinition(J2Propagator other)
true if it does. Derived classes MUST override this method and check
all new fields introduced by the derived class for definitional equivalence. It is NOT necessary
to check base class fields because the base class will already have done that. When overriding this method,
you should NOT call the base implementation because it will return false for all derived-class instances.
Derived classes should check the type of other to preserve the symmetric nature of IEquatableDefinition.isSameDefinition(java.lang.Object).other - The other instance to compare to this one.true if the two objects are defined equivalently; otherwise false.protected int computeCurrentDefinitionHashCode()
J2Propagator.checkForSameDefinition(agi.foundation.propagators.CartesianOnePointPropagator) method.computeCurrentDefinitionHashCode in class CartesianOnePointPropagatorpublic void enumerateDependencies(DependencyEnumerator enumerator)
DependencyEnumerator#enumerate(T) for each object that this object directly depends upon.
Derived classes which contain additional dependencies MUST override this method, call the base
implementation, and enumerate dependencies introduced by the derived class.enumerateDependencies in interface IEnumerateDependenciesenumerateDependencies in class DefinitionalObjectenumerator - The enumerator that is informed of the dependencies of this object.@Nonnull public final JulianDate getOrbitEpoch()
public final void setOrbitEpoch(@Nonnull JulianDate value)
@Nonnull public final ReferenceFrame getReferenceFrame()
public final void setReferenceFrame(@Nonnull ReferenceFrame value)
protected ReferenceFrame getMotionReferenceFrame()
getMotionReferenceFrame in class CartesianOnePointPropagator@Nonnull public final ModifiedKeplerianElements getInitialConditions()
GravitationalParameter (get / set).IllegalStateException - Thrown if the InitialConditions (get / set) are set to
an open orbit. (i.e. OrbitType (get) is not Circular or Elliptical.)public final void setInitialConditions(@Nonnull ModifiedKeplerianElements value)
GravitationalParameter (get / set).IllegalStateException - Thrown if the InitialConditions (get / set) are set to
an open orbit. (i.e. OrbitType (get) is not Circular or Elliptical.)public final double getGravitationalParameter()
public final void setGravitationalParameter(double value)
public final double getJ2ZonalHarmonicCoefficient()
public final void setJ2ZonalHarmonicCoefficient(double value)
public final double getReferenceDistance()
public final void setReferenceDistance(double value)
public MotionEvaluator1<Cartesian> getEvaluator(EvaluatorGroup group)
Gets an evaluator that can propagate at individual dates.
This evaluator propagates the orbit state from InitialConditions (get / set) at OrbitEpoch (get / set)
based on the GravitationalParameter (get / set), J2ZonalHarmonicCoefficient (get / set) and
ReferenceDistance (get / set).
The result of evaluating will be a
Motion<Cartesian> corresponding to the orbital position and velocity
at the given JulianDate expressed in the propagator's ReferenceFrame (get / set).
getEvaluator in class CartesianOnePointPropagatorgroup - The group with which to associate the new evaluator. By grouping evaluators
that are often evaluated at the same Julian dates, common computations can be performed only once
for the entire group instead of multiple times for each evaluator.ArgumentNullException - Thrown when the group is null.CartesianOnePointPropagator.createPoint()