Package org.orekit.propagation.events

Class AngularSeparationDetector

java.lang.Object

org.orekit.propagation.events.AbstractDetector<AngularSeparationDetector>

org.orekit.propagation.events.AngularSeparationDetector

All Implemented Interfaces:

EventDetector

public class AngularSeparationDetector
extends AbstractDetector<AngularSeparationDetector>

Detects when spacecraft comes close to a moving beacon, as seen from a moving observer.

The main use case for this detector is when the observer is in fact a ground station, modeled as a TopocentricFrame and when the beacon is the Sun, for computing interferences for the telemetry link. Another similar case is when the beacon is another spacecraft, for interferences computation.

The default handler behavior is to stop propagation when spacecraft enters the proximity zone. This can be changed by calling AbstractDetector.withHandler(EventHandler) after construction.

Since:

8.0

Author:

Luc Maisonobe

See Also:

Propagator.addEventDetector(EventDetector)

Field Summary

Fields inherited from class org.orekit.propagation.events.AbstractDetector

DEFAULT_MAX_ITER, DEFAULT_MAXCHECK, DEFAULT_THRESHOLD

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AngularSeparationDetector(AdaptableInterval maxCheck, double threshold, int maxIter, EventHandler handler, PVCoordinatesProvider beacon, PVCoordinatesProvider observer, double proximityAngle)	Protected constructor with full parameters.
	AngularSeparationDetector(PVCoordinatesProvider beacon, PVCoordinatesProvider observer, double proximityAngle)	Build a new angular separation detector.

Method Summary

Modifier and Type	Method	Description
protected AngularSeparationDetector	create(AdaptableInterval newMaxCheck, double newThreshold, int newMaxIter, EventHandler newHandler)	Build a new instance.
double	g(SpacecraftState s)	Compute the value of the switching function.
PVCoordinatesProvider	getBeacon()	Get the beacon at the center of the proximity zone.
PVCoordinatesProvider	getObserver()	Get the observer for the spacecraft.
double	getProximityAngle()	Get the proximity angle (rad).

Methods inherited from class org.orekit.propagation.events.AbstractDetector

create, getDetectionSettings, getHandler, getMaxCheckInterval, getMaxIterationCount, getThreshold, init, isForward, withDetectionSettings, withHandler, withMaxCheck, withMaxCheck, withMaxIter, withThreshold

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.orekit.propagation.events.EventDetector

finish

Constructor Detail

AngularSeparationDetector

public AngularSeparationDetector(PVCoordinatesProvider beacon,
                                 PVCoordinatesProvider observer,
                                 double proximityAngle)

Build a new angular separation detector.

Parameters:

beacon - beacon at the center of the proximity zone

observer - observer for the spacecraft, that may also see the beacon at the same time if they are too close to each other

proximityAngle - proximity angle as seen from observer, at which events are triggered (rad)

AngularSeparationDetector

protected AngularSeparationDetector(AdaptableInterval maxCheck,
                                    double threshold,
                                    int maxIter,
                                    EventHandler handler,
                                    PVCoordinatesProvider beacon,
                                    PVCoordinatesProvider observer,
                                    double proximityAngle)

Protected constructor with full parameters.

This constructor is not public as users are expected to use the builder API with the various withXxx() methods to set up the instance in a readable manner without using a huge amount of parameters.

Parameters:

maxCheck - maximum checking interval

threshold - convergence threshold (s)

maxIter - maximum number of iterations in the event time search

handler - event handler to call at event occurrences

beacon - beacon at the center of the proximity zone

observer - observer for the spacecraft, that may also see the beacon at the same time if they are too close to each other

proximityAngle - proximity angle as seen from observer, at which events are triggered (rad)

Method Detail

create

protected AngularSeparationDetector create(AdaptableInterval newMaxCheck,
                                           double newThreshold,
                                           int newMaxIter,
                                           EventHandler newHandler)

Build a new instance.

Specified by:

create in class AbstractDetector<AngularSeparationDetector>

Parameters:

newMaxCheck - maximum checking interval (s)

newThreshold - convergence threshold (s)

newMaxIter - maximum number of iterations in the event time search

newHandler - event handler to call at event occurrences

Returns:

a new instance of the appropriate sub-type

getBeacon

public PVCoordinatesProvider getBeacon()

Get the beacon at the center of the proximity zone.

Returns:

beacon at the center of the proximity zone

getObserver

public PVCoordinatesProvider getObserver()

Get the observer for the spacecraft.

Returns:

observer for the spacecraft

getProximityAngle

public double getProximityAngle()

Get the proximity angle (rad).

Returns:

the proximity angle

g

public double g(SpacecraftState s)

Compute the value of the switching function.

This function measures the angular separation between beacon and spacecraft as seen from the observer minus the proximity angle. It therefore triggers decreasing events when the spacecraft enters the proximity zone and increasing events when it leaves the proximity zone.

No shadowing effect is taken into account, so this method is computed and may trigger events even when the spacecraft is below horizon for an observer which is a ground station. If such effects must be taken into account the detector must be associated with a predicate filter where the predicate function is based on elevation.

Parameters:

s - the current state information: date, kinematics, attitude

Returns:

value of the switching function