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Guide to Swift data processing and analysis

The pipeline processing of the Swift Data is performed at the Swift Data Center (SDC) at the Goddard Space Flight Center (GSFC). Data received from the spacecraft, via telemetry dumps to the Malindi Ground Station, (Level 0 files) are used to create FITS files containing image and event data from from the 3 instruments. These files are then sent through the pipeline, which leads to the formation of calibrated images, cleaned event lists and light-curves/spectra for the GRB afterglow candidate (where possible).

The image below shows a flow diagram indicating the different levels of Swift data processing. The raw telemetry is converted to Level 1 FITS files, which then undergo a small amount of processing. Level 2 calibrated event lists and sky images are produced after data screening and coordinate transformation. The Level 2 products then go through the scripts for each instrument, leading to spectra, light-curves and combined sky images (Level 3 files).

Data-processing flow diagram

These products are then placed on the Quick Look data area, from where they will be available to the GRB community. After a week, the data will be archived by the data centres in the UK and Italy and by HEASARC (in the USA).

Assuming all the data from one observation is saved in one master directory, there will be many subdirectories under the main [obsid] (e.g. 00020521001 is a typical name for the master directory on the UK Quick Look site; the US site is slightly different). The version number given on the QL site indicates how many times the data have been through the pipeline. A brief overview of the system for assigning Observation IDs is available.