public class AttitudesSequence extends Object implements AttitudeProvider
Only one attitude provider in the sequence is in an active state. When one of the switch event associated with the active provider occurs, the active provider becomes the one specified with the event. A simple example is a provider for the sun lighted part of the orbit and another provider for the eclipse time. When the sun lighted provider is active, the eclipse entry event is checked and when it occurs the eclipse provider is activated. When the eclipse provider is active, the eclipse exit event is checked and when it occurs the sun lighted provider is activated again. This sequence is a simple loop.
An active attitude provider may have several switch events and next provider settings, leading to different activation patterns depending on which events are triggered first. An example of this feature is handling switches to safe mode if some contingency condition is met, in addition to the nominal switches that correspond to proper operations. Another example is handling of maneuver mode.
| Modifier and Type | Class and Description |
|---|---|
static interface |
AttitudesSequence.SwitchHandler
Interface for attitude switch notifications.
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| Constructor and Description |
|---|
AttitudesSequence()
Constructor for an initially empty sequence.
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| Modifier and Type | Method and Description |
|---|---|
<T extends EventDetector> |
addSwitchingCondition(AttitudeProvider past,
AttitudeProvider future,
T switchEvent,
boolean switchOnIncrease,
boolean switchOnDecrease,
double transitionTime,
AngularDerivativesFilter transitionFilter,
AttitudesSequence.SwitchHandler handler)
Add a switching condition between two attitude providers.
|
<T extends EventDetector> |
addSwitchingCondition(AttitudeProvider past,
T switchEvent,
boolean switchOnIncrease,
boolean switchOnDecrease,
AttitudeProvider future)
Deprecated.
|
Attitude |
getAttitude(PVCoordinatesProvider pvProv,
AbsoluteDate date,
Frame frame)
Compute the attitude corresponding to an orbital state.
|
void |
registerSwitchEvents(Propagator propagator)
Register all wrapped switch events to the propagator.
|
void |
resetActiveProvider(AttitudeProvider provider)
Reset the active provider.
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public AttitudesSequence()
public void resetActiveProvider(AttitudeProvider provider)
provider - provider to activatepublic void registerSwitchEvents(Propagator propagator)
This method must be called once before propagation, after the
switching conditions have been set up by calls to addSwitchingCondition.
propagator - propagator that will handle the events@Deprecated public <T extends EventDetector> void addSwitchingCondition(AttitudeProvider past, T switchEvent, boolean switchOnIncrease, boolean switchOnDecrease, AttitudeProvider future) throws OrekitException
addSwitchingCondition(AttitudeProvider,
AttitudeProvider, EventDetector, boolean, boolean, double, AngularDerivativesFilter,
SwitchHandler)
This method simply calls addSwitchingCondition with
the transition time set to twice the event threshold, transition filter set to match
rotation only and the switch handler set to null.
T - class type for the generic versionpast - attitude provider applicable for times in the switch event occurrence pastswitchEvent - event triggering the attitude providers switchswitchOnIncrease - if true, switch is triggered on increasing eventswitchOnDecrease - if true, switch is triggered on decreasing eventfuture - attitude provider applicable for times in the switch event occurrence futureOrekitException - if transition time is shorter than event convergence threshold
or if transition order is out of the [0; 2] range (never really thrown here)public <T extends EventDetector> void addSwitchingCondition(AttitudeProvider past, AttitudeProvider future, T switchEvent, boolean switchOnIncrease, boolean switchOnDecrease, double transitionTime, AngularDerivativesFilter transitionFilter, AttitudesSequence.SwitchHandler handler) throws OrekitException
The past and future attitude providers are defined with regard
to the natural flow of time. This means that if the propagation is forward, the
propagator will switch from past provider to future provider at
event occurrence, but if the propagation is backward, the propagator will switch
from future provider to past provider at event occurrence. The
transition between the two attitude laws is not instantaneous, the switch event
defines the start of the transition (i.e. when leaving the past attitude
law and entering the interpolated transition law). The end of the transition
(i.e. when leaving the interpolating transition law and entering the future
attitude law) occurs at switch time plus transitionTime.
An attitude provider may have several different switch events associated to it. Depending on which event is triggered, the appropriate provider is switched to.
The switch events specified here must not be registered to the
propagator directly. The proper way to register these events is to
call registerSwitchEvents(Propagator) once after all switching
conditions have been set up. The reason for this is that the events will
be wrapped before being registered.
If the underlying detector has an event handler associated to it, this handler
will be triggered (i.e. its eventOccurred method will be called), regardless
of the event really triggering an attitude switch or not. As an example, if an
eclipse detector is used to switch from day to night attitude mode when entering
eclipse, with switchOnIncrease set to false and switchOnDecrease
set to true. Then a handler set directly at eclipse detector level would
be triggered at both eclipse entry and eclipse exit, but attitude switch would
occur only at eclipse entry. Note that for the sake of symmetry, the
transition start and end dates should match for both forward and backward propagation.
This implies that for backward propagation, we have to compensate for the transitionTime when looking for the event. An unfortunate consequence is that the
eventOccurred method may appear to be called out of sync with respect to the
propagation (it will be called when propagator reaches transition end, despite it
refers to transition start, as per transitionTime compensation), and if the
method returns EventHandler.Action.STOP, it will stop at the end of the
transition instead of at the start. For these reasons, it is not recommended to
set up an event handler for events that are used to switch attitude. If an event
handler is needed for other purposes, a second handler should be registered to
the propagator rather than relying on the side effects of attitude switches.
The smoothness of the transition between past and future attitude laws can be tuned
using the transitionTime and transitionOrder parameters. The transitionTime parameter specifies how much time is spent to switch from one law to
the other law. It should be larger than the event convergence threshold in order to ensure attitude continuity. The transitionOrder parameter specifies the order of the attitude time derivatives that
should match at the boundaries between past attitude law and transition law on one side,
and between transition law and future law on the other side. Order 0 means only the
rotation should be identical, order 1 means both rotation and rotation rate should be
identical, order 2 means both rotation, rotation rate and rotation acceleration should
be identical. During the transition, the attitude law is computed by interpolating
between past attitude law at switch time and future attitude law at current intermediate
time.
T - class type for the switch eventpast - attitude provider applicable for times in the switch event occurrence pastfuture - attitude provider applicable for times in the switch event occurrence futureswitchEvent - event triggering the attitude providers switchswitchOnIncrease - if true, switch is triggered on increasing eventswitchOnDecrease - if true, switch is triggered on decreasing eventtransitionTime - duration of the transition between the past and future attitude lawstransitionFilter - order at which the transition law time derivatives
should match past and future attitude lawshandler - handler to call for notifying when switch occurs (may be null)OrekitException - if transition time is shorter than event convergence thresholdpublic Attitude getAttitude(PVCoordinatesProvider pvProv, AbsoluteDate date, Frame frame) throws OrekitException
getAttitude in interface AttitudeProviderpvProv - local position-velocity provider around current datedate - current dateframe - reference frame from which attitude is computedOrekitException - if attitude cannot be computedCopyright © 2002-2016 CS Systèmes d'information. All rights reserved.