Package org.orekit.propagation.events

This package provides interfaces and classes dealing with events occurring during propagation. It is used when EventDetector instances are registered to any Propagator. When the event associated with the detector occurs, the propagator interrupts the propagation and calls the eventOccurred method of the event handler, which can do whatever the user want and either stop or resume propagation, optionally resetting the state.

If the registered events detectors are configured to stop propagation when triggered, the propagator can be run with an arbitrary large target date, relying on the events occurrence to stop propagation exactly at the right time.

The package provides some predefined events:

• AlignmentDetector detects satellite/body alignment (and by default stop when reaching alignment)
• AngularSeparationDetector detects angular separation thresholds crossing between spacecraft and a beacon (typically the Sun) as seen from an observer (typically a ground station)
• AltitudeDetector detects altitude crossing (and by default stop at descending)
• ApsideDetector detects apside crossing (and by default stop at perigee)
• DateDetector detects occurrence of a predefine instant (and by default stop there)
• EclipseDetector detects satellite entering/exiting an eclipse (and by default stop on exit)
• ElevationDetector detects satellite raising/setting (and by default stop at setting)
• ElevationExtremumDetector detects satellite maximum/minimum elevation (and by default stop at minimum)
• FieldOfViewDetector detects moving target entering/exiting satellite sensor Field Of View with an arbitrarily shaped boundary (and by default continue on entry and stop on exit)
• FootprintOverlapDetector detects geographic zone entering or exiting Field Of View of a spacecraft sensor (and by default stop at zone exit)
• GeographicZoneDetector detects geographic boundaries crossings (and by default stop at zone exit)
• GroundFieldOfViewDetector detects spacecraft entering/exiting ground based Field Of View with an arbitrarily shaped boundary (and by default continue on entry and stop on exit)
• LatitudeCrossingDetector detects satellite crossing a parallel (and by default stop at northward crossing)
• LatitudeExtremumDetector detects satellite maximum/minimum latitude (and by default stop at minimum)
• LongitudeCrossingDetector detects satellite crossing a meridian (the increasing/decreasing flag is irrelevant for this detector)
• LongitudeExtremumDetector detects satellite maximum/minimum longitude (and by default stop at minimum)
• NodeDetector detects node crossing (and by default stop at ascending node)
• PositionAngleDetector detects anomaly, latitude argument or longitude argument crossings, with either true eccentric or mean angles (the increasing/decreasing flag is irrelevant for this detector)

In addition to raw events, the class also provides EventsLogger to gather all events that occurred during a propagation, EventShifter which allows to slightly shift an event in time (for example to trigger something say 5 minutes before eclipse entry), EventSlopeFilter and EventEnablingPredicateFilter to trigger only specific types of events, without losing computation time by locating events user is not interested in. Also the BooleanDetector allows the user to combine other event detectors using Boolean logic.

The low level interfaces and classes are heavily based on similar classes from the ode.events package from the Hipparchus library. The changes are mainly adaptations of the signatures to space dynamics.

• the type of dependent variable t has been changed from double to AbsoluteDate
• the type of state vector y has been changed from double[] to SpacecraftState

Author:

Luc Maisonobe, Pascal Parraud

Interface Summary

Interface	Description
AdaptableInterval	This interface represents an event checking interval that depends on state.
EnablingPredicate	This interface represents an event enabling predicate function.
EventDetector	This interface represents space-dynamics aware events detectors.
EventDetectorsProvider	Interface for building event detectors for force models and maneuver parameters.
FieldAdaptableInterval<T extends CalculusFieldElement<T>>	This interface represents an event checking interval that depends on state.
FieldEnablingPredicate<T extends CalculusFieldElement<T>>	This interface represents an event enabling predicate function.
FieldEventDetector<T extends CalculusFieldElement<T>>	This interface represents space-dynamics aware events detectors.

Class Summary

Class	Description
AbstractDetector<T extends AbstractDetector<T>>	Common parts shared by several orbital events finders.
AdapterDetector	Base class for adapting an existing detector.
AlignmentDetector	Finder for satellite/body alignment events in orbital plane.
AltitudeDetector	Finder for satellite altitude crossing events.
AngularSeparationDetector	Detects when spacecraft comes close to a moving beacon, as seen from a moving observer.
AngularSeparationFromSatelliteDetector	Detects when two moving objects come close to each other, as seen from spacecraft.
ApsideDetector	Finder for apside crossing events.
BooleanDetector	This class provides AND and OR operations for event detectors.
DateDetector	Finder for date events.
EclipseDetector	Finder for satellite eclipse related events.
ElevationDetector	Finder for satellite raising/setting events that allows for the setting of azimuth and/or elevation bounds or a ground azimuth/elevation mask input.
ElevationExtremumDetector	Detector for elevation extremum with respect to a ground point.
EventEnablingPredicateFilter	Wrapper used to detect events only when enabled by an external predicated function.
EventShifter	Wrapper shifting events occurrences times.
EventsLogger	This class logs events detectors events during propagation.
EventsLogger.LoggedEvent	Class for logged events entries.
EventSlopeFilter<T extends EventDetector>	Wrapper used to detect only increasing or decreasing events.
EventState<T extends EventDetector>	This class handles the state for one event detector during integration steps.
EventState.EventOccurrence	Class to hold the data related to an event occurrence that is needed to decide how to modify integration.
ExtremumApproachDetector	Finder for extremum approach events.
FieldAbstractDetector<D extends FieldAbstractDetector<D,T>,T extends CalculusFieldElement<T>>	Common parts shared by several orbital events finders.
FieldAdapterDetector<T extends CalculusFieldElement<T>>	Base class for adapting an existing detector.
FieldAltitudeDetector<T extends CalculusFieldElement<T>>	Finder for satellite altitude crossing events.
FieldApsideDetector<T extends CalculusFieldElement<T>>	Finder for apside crossing events.
FieldBooleanDetector<T extends CalculusFieldElement<T>>	This class provides AND and OR operations for event detectors.
FieldDateDetector<T extends CalculusFieldElement<T>>	Finder for date events.
FieldEclipseDetector<T extends CalculusFieldElement<T>>	Finder for satellite eclipse related events.
FieldElevationDetector<T extends CalculusFieldElement<T>>	Finder for satellite raising/setting events that allows for the setting of azimuth and/or elevation bounds or a ground azimuth/elevation mask input.
FieldElevationExtremumDetector<T extends CalculusFieldElement<T>>	Detector for elevation extremum with respect to a ground point.
FieldEventEnablingPredicateFilter<T extends CalculusFieldElement<T>>	Wrapper used to detect events only when enabled by an external predicated function.
FieldEventsLogger<T extends CalculusFieldElement<T>>	This class logs events detectors events during propagation.
FieldEventsLogger.FieldLoggedEvent<T extends CalculusFieldElement<T>>	Class for logged events entries.
FieldEventSlopeFilter<D extends FieldEventDetector<T>,T extends CalculusFieldElement<T>>	Wrapper used to detect only increasing or decreasing events.
FieldEventState<D extends FieldEventDetector<T>,T extends CalculusFieldElement<T>>	This class handles the state for one event detector during integration steps.
FieldEventState.EventOccurrence<T extends CalculusFieldElement<T>>	Class to hold the data related to an event occurrence that is needed to decide how to modify integration.
FieldFunctionalDetector<T extends CalculusFieldElement<T>>	A detector that implements the FieldFunctionalDetector.g(FieldSpacecraftState) function using a lambda that can be set using FieldFunctionalDetector.withFunction(Function).
FieldLatitudeCrossingDetector<T extends CalculusFieldElement<T>>	Detector for geographic latitude crossing.
FieldLongitudeCrossingDetector<T extends CalculusFieldElement<T>>	Detector for geographic longitude crossing.
FieldNegateDetector<T extends CalculusFieldElement<T>>	An event detector that negates the sign on another event detector's g function.
FieldNodeDetector<T extends CalculusFieldElement<T>>	Finder for node crossing events.
FieldOfViewDetector	Finder for target entry/exit events with respect to a satellite sensor Field Of View.
FieldParameterDrivenDateIntervalDetector<T extends CalculusFieldElement<T>>	Detector for date intervals that may be offset thanks to parameter drivers.
FootprintOverlapDetector	Detector triggered by geographical region entering/leaving a spacecraft sensor Field Of View.
FunctionalDetector	A detector that implements the FunctionalDetector.g(SpacecraftState) function using a lambda that can be set using FunctionalDetector.withFunction(ToDoubleFunction).
GeographicZoneDetector	Detector for entry/exit of a zone defined by geographic boundaries.
GroundAtNightDetector	Detector for ground location being at night.
GroundFieldOfViewDetector	Finder for satellite entry/exit events with respect to a sensor Field Of View attached to an arbitrary frame.
HaloXZPlaneCrossingDetector	Detector for XZ Plane crossing.
InterSatDirectViewDetector	Detector for inter-satellites direct view (i.e.
LatitudeCrossingDetector	Detector for geographic latitude crossing.
LatitudeExtremumDetector	Detector for geographic latitude extremum.
LongitudeCrossingDetector	Detector for geographic longitude crossing.
LongitudeExtremumDetector	Detector for geographic longitude extremum.
MagneticFieldDetector	Detector for Earth magnetic field strength.
NegateDetector	An event detector that negates the sign on another event detector's g function.
NodeDetector	Finder for node crossing events.
ParameterDrivenDateIntervalDetector	Detector for date intervals that may be offset thanks to parameter drivers.
PositionAngleDetector	Detector for in-orbit position angle.

Enum Summary

Enum	Description
FilterType	Enumerate for filtering events.
VisibilityTrigger	Enumerate for triggering visibility of spherical bodies.