Tutorials 4.1 Events

What is an Event ?

An EventDetector corresponds to an object that will allow to a propagator to determine when this event will occurred.

PATRIUS will already propose a great amount of predefined events (anomaly, AOL, altitude, eclipse, ...). These events may be called with "by default" values or may be customized by defining:

• its maximum check interval (in seconds)
• the threshold value below which the convergence is acquired (in seconds)
• the fact that the event will be checked several time or not.

The following code example shows how to define an AOL detector with all these possibilities.

Code example: AOL event detector

Using AbstractDetector class

If you have not found a predefined event detector into the PATRIUS list, you can build yourself you own detector using the AbstractDetector class.

In such a case, you will have to redefined:

• eventOccurred() method ; when the event has occured, this method will be called by the propagator and will return the appropriate action
• g() method ; this method will return a double value which trigger the event when it will reach zero (+/- the threshold)
• shouldBeRemoved() method

Code example: Event using AbstractDetector class

Using EventDetector interface

if you want to customize deeper your event detector, rather than to use AbstractDetector class, you may use EventDetector interface.

In such a case, you will have to redefined:

• eventOccurred() method ; when the event has occured, this method will be called by the propagator and will return the appropriate action
• getMaxCheckInterval() method ; this method will return a double value which trigger the event when it will reach zero (+/- the threshold)
• getMaxIterationCount() method
• getSlopeSelection() method
• getThreshold() method
• init() method
• resetState() method
• shouldBeRemoved() method

Code example: Event using EventDetector interface