University of Wisconsin-Madison

Processing and Filtering

The raw data rates collected by the IceCube detector far exceed our daily satellite bandwidth allocations. To allow physics analysis to happen as quickly as possible, the first level of reconstruction and event filtering happens in near real-time at the South Pole station. Events selected as physically interesting by this system are queued for immediate transmission over the satellite so in-depth analysis of these events can begin immediately in the North.

The Online Processing and Filtering system is responsible for accepting raw, triggered events from the data acquisition system (DAQ) using the interfaces of the DAQ Dispatch system. Any needed calibrations are applied and reconstruction and filtering algorithms are performed on the data. The raw data are written to disk in a format that contains the results of any reconstructions and filters performed, and is categorized into data sets for satellite transmission to the Northern hemisphere and/or archiving to tape by the SPADE system. This system needs to be expandable to handle to growth of the IceCube detector and any growth in the complexity of the reconstruction and filtering algorithms used at the South Pole.

Reconstruction and filtering modules are provided by the physics working groups in the collaboration and are written in the IceTray analysis framework. Using this system, modules written for offline analysis can be "plugged in" to the online filtering system with little or no changes. By using the same analysis framework in software development systems and in the online analysis and filtering system, new advances in data filtering can quickly be implemented at the detector.