public interface Propagator extends PVCoordinatesProvider
This interface is the top-level abstraction for orbit propagation. It only allows propagation to a predefined date. It is implemented by analytical models which have no time limit, by orbit readers based on external data files, by numerical integrators using rich force models and by continuous models built after numerical integration has been completed and dense output data as been gathered.
Note that one single propagator cannot be called from multiple threads.
Its configuration can be changed as there is at least a resetInitialState(SpacecraftState) method, and even propagators that do
not support resetting state (like the TLEPropagator do
cache some internal data during computation. However, as long as they
are configured with independent building blocks (mainly event handlers
and step handlers that may preserve some internal state), and as long
as they are called from one thread only, they can be used in
multi-threaded applications. Synchronizing several propagators to run in
parallel is also possible using PropagatorsParallelizer.
| Modifier and Type | Field and Description |
|---|---|
static double |
DEFAULT_MASS
Default mass.
|
| Modifier and Type | Method and Description |
|---|---|
void |
addAdditionalStateProvider(AdditionalStateProvider additionalStateProvider)
Add a set of user-specified state parameters to be computed along with the orbit propagation.
|
<T extends EventDetector> |
addEventDetector(T detector)
Add an event detector.
|
void |
clearEventsDetectors()
Remove all events detectors.
|
default void |
clearStepHandlers()
Remove all step handlers.
|
List<AdditionalStateProvider> |
getAdditionalStateProviders()
Get an unmodifiable list of providers for additional state.
|
AttitudeProvider |
getAttitudeProvider()
Get attitude provider.
|
static AttitudeProvider |
getDefaultLaw(Frames frames)
Get a default law using the given frames.
|
EphemerisGenerator |
getEphemerisGenerator()
Set up an ephemeris generator that will monitor the propagation for building
an ephemeris from it once completed.
|
Collection<EventDetector> |
getEventsDetectors()
Get all the events detectors that have been added.
|
Frame |
getFrame()
Get the frame in which the orbit is propagated.
|
SpacecraftState |
getInitialState()
Get the propagator initial state.
|
String[] |
getManagedAdditionalStates()
Get all the names of all managed states.
|
StepHandlerMultiplexer |
getMultiplexer()
Get the multiplexer holding all step handlers.
|
boolean |
isAdditionalStateManaged(String name)
Check if an additional state is managed.
|
SpacecraftState |
propagate(AbsoluteDate target)
Propagate towards a target date.
|
SpacecraftState |
propagate(AbsoluteDate start,
AbsoluteDate target)
Propagate from a start date towards a target date.
|
void |
resetInitialState(SpacecraftState state)
Reset the propagator initial state.
|
void |
setAttitudeProvider(AttitudeProvider attitudeProvider)
Set attitude provider.
|
default void |
setStepHandler(double h,
OrekitFixedStepHandler handler)
Set a single handler for fixed stepsizes.
|
default void |
setStepHandler(OrekitStepHandler handler)
Set a single handler for variable stepsizes.
|
default MatricesHarvester |
setupMatricesComputation(String stmName,
RealMatrix initialStm,
DoubleArrayDictionary initialJacobianColumns)
Set up computation of State Transition Matrix and Jacobians matrix with respect to parameters.
|
getPVCoordinatesstatic final double DEFAULT_MASS
static AttitudeProvider getDefaultLaw(Frames frames)
frames - the set of frames to use.StepHandlerMultiplexer getMultiplexer()
default void clearStepHandlers()
This convenience method is equivalent to call getMultiplexer().clear()
getMultiplexer(),
StepHandlerMultiplexer.clear()default void setStepHandler(double h,
OrekitFixedStepHandler handler)
This convenience method is equivalent to call getMultiplexer().clear()
followed by getMultiplexer().add(h, handler)
h - fixed stepsize (s)handler - handler called at the end of each finalized stepgetMultiplexer(),
StepHandlerMultiplexer.add(double, OrekitFixedStepHandler)default void setStepHandler(OrekitStepHandler handler)
This convenience method is equivalent to call getMultiplexer().clear()
followed by getMultiplexer().add(handler)
handler - handler called at the end of each finalized stepgetMultiplexer(),
StepHandlerMultiplexer.add(OrekitStepHandler)EphemerisGenerator getEphemerisGenerator()
This generator can be used when the user needs fast random access to the orbit state at any time between the initial and target times. A typical example is the implementation of search and iterative algorithms that may navigate forward and backward inside the propagation range before finding their result even if the propagator used is integration-based and only goes from one initial time to one target time.
Beware that when used with integration-based propagators, the generator will store all intermediate results. It is therefore memory intensive for long integration-based ranges and high precision/short time steps. When used with analytical propagators, the generator only stores start/stop time and a reference to the analytical propagator itself to call it back as needed, so it is less memory intensive.
The returned ephemeris generator will be initially empty, it will be filled
with propagation data when a subsequent call to either propagate(target) or propagate(start, target) is called. The proper way to use this method is
therefore to do:
EphemerisGenerator generator = propagator.getEphemerisGenerator(); propagator.propagate(target); BoundedPropagator ephemeris = generator.getGeneratedEphemeris();
SpacecraftState getInitialState()
void resetInitialState(SpacecraftState state)
state - new initial state to considervoid addAdditionalStateProvider(AdditionalStateProvider additionalStateProvider)
additionalStateProvider - provider for additional stateList<AdditionalStateProvider> getAdditionalStateProviders()
boolean isAdditionalStateManaged(String name)
Managed states are states for which the propagators know how to compute
its evolution. They correspond to additional states for which a
provider has been registered by calling the
addAdditionalStateProvider method.
Additional states that are present in the initial state
but have no evolution method registered are not considered as managed states.
These unmanaged additional states are not lost during propagation, though. Their
value are piecewise constant between state resets that may change them if some
event handler resetState method is called at an event occurrence and happens
to change the unmanaged additional state.
name - name of the additional stateString[] getManagedAdditionalStates()
<T extends EventDetector> void addEventDetector(T detector)
T - class type for the generic versiondetector - event detector to addclearEventsDetectors(),
getEventsDetectors()Collection<EventDetector> getEventsDetectors()
addEventDetector(EventDetector),
clearEventsDetectors()void clearEventsDetectors()
AttitudeProvider getAttitudeProvider()
void setAttitudeProvider(AttitudeProvider attitudeProvider)
attitudeProvider - attitude providerFrame getFrame()
The propagation frame is the definition frame of the initial state, so this method should be called after this state has been set, otherwise it may return null.
resetInitialState(SpacecraftState)default MatricesHarvester setupMatricesComputation(String stmName, RealMatrix initialStm, DoubleArrayDictionary initialJacobianColumns)
If this method is called, both State Transition Matrix and Jacobians with respect to the force models parameters that will be selected when propagation starts will be automatically computed, and the harvester will allow to retrieve them.
The arguments for initial matrices must be compatible with the orbit type and position angle that will be used by the propagator.
The default implementation throws an exception as the method is not supported by all propagators.
stmName - State Transition Matrix state nameinitialStm - initial State Transition Matrix ∂Y/∂Y₀,
if null (which is the most frequent case), assumed to be 6x6 identityinitialJacobianColumns - initial columns of the Jacobians matrix with respect to parameters,
if null or if some selected parameters are missing from the dictionary, the corresponding
initial column is assumed to be 0SpacecraftState propagate(AbsoluteDate target)
Simple propagators use only the target date as the specification for computing the propagated state. More feature rich propagators can consider other information and provide different operating modes or G-stop facilities to stop at pinpointed events occurrences. In these cases, the target date is only a hint, not a mandatory objective.
target - target date towards which orbit state should be propagatedSpacecraftState propagate(AbsoluteDate start, AbsoluteDate target)
Those propagators use a start date and a target date to compute the propagated state. For propagators using event detection mechanism, if the provided start date is different from the initial state date, a first, simple propagation is performed, without processing any event computation. Then complete propagation is performed from start date to target date.
start - start date from which orbit state should be propagatedtarget - target date to which orbit state should be propagatedCopyright © 2002-2022 CS GROUP. All rights reserved.