Archive structure

Data organization

Each of the data sets that comprise the Swift archive are organized in distinct directories as follows:

• obs : contains the Swift data telemetered from the Malindi ground station and processed on the ground at the Swift Data Center. These data are organized by sequence number, each corresponding to an observation.

• tdrss : contains the first response to the trigger sent to the ground via TDRSS. Both false and good trigger are included. These data are organized by sequence number, however they do no necessarily correspond to an observation as for example false triggers.

• trend : contains instrument monitoring data telemetered from the Malindi ground station and derived trend data. These data are organized by instrument first and, within directories each containing a specific type of data.

To limit the number of files in each of the above directories, data are subdivided in interval of one months and, within these are organized as described above. The time interval directories are named YYYY_NN, where where YYYY is the year and NN defines the month within that year.

       /obs                    /tdrss                    /trend
/2004_12  /2005_01 ...    /2004_12  /2005_01 ...    /2004_12  /2005_01 ...
    |                        |                       |
/sequence                /sequence            /xrt /bat /uvot /misc
                                                |
                                              /type

The results of the surveys and the derived GRB products will be located in seperate dedicated directories and will be documented here after these data start to arrive in the archive.

The 'obs' data directory structure

The science data are located under the /obs main directory. Each sequence is divided into the following subdirectories :

• /auxil : contains files common to all instruments such as attitude and orbit as well as a catalog listing all the files present in the sequence.
• /log : contains html files reporting logs on the data processing. item /bat : contains all the science and HK files related to the BAT instrument. The data within are further sub-divided into directories related to the data mode and file types.
• /uvot : contains all the science and HK files related to the UVOT instrument. The data within are further sub-divided into directories related to the data mode and file types.
• /xrt : contains all the science and HK files related to the XRT instrument. The data within are further sub-divided into directories related to the data mode and file types.
• /tdrss : contains the science TDRSS messages related to thedata included in the sequence.

The /auxil and /log directories are always present for every sequence. The others may or may not be present, depending on the observation type and/or if the instrument was or was not generating data during a specific observation. Specifically the /tdrss directory is typically present only in AT observations, however it may also be present in some calibration PPT observations. Sequences related to triggers that do not generate a slew will contain only data in the /bat directory but not in the /xrt and /uvot directories.
Each of the instrument directory is subdivided in subdirectories. For the /xrt and /uvot directories there are :

• /event : contains Level 1 and Level 2 files of science data corresponding to data modes that use event FITS file as their format.
• /image : contains Level 1 and Level 2 files of science data corresponding to data modes that use image FITS file as their format.

• /hk : contains housekeeping files related to the specific instrument.
• /products : contains all the high-level products derived from the science files. These are lightcurves and spectra of the targetted source, and images of the entire FOV. They are provided as FITS files with their plots as a GIF.

The /bat directory structure instead includes the following directories:

• /event : contains Level 1 (and Level 2) files of science data corresponding to the data mode that use event FITS file as their format. This directory is typically present when there is an AT observation.
• /survey : contains Level 1 and Level 2 files of science data corresponding to the BAT survey mode. The FITS format files contain a two-dimensional array giving an 80-channel spectrum for each detector.
• /rate : contains the science data corresponding to the BAT rate modes, e.g. lightcurves from different parts of the detector array. They use a lightcurve FITS format to store the multi-channel counts.
• /pulsar : contains the science data corresponding to the BAT pulsar mode.
• /masktag : contains the science data corresponding to the BAT masktag mode. During an observation the BAT can 'tag' the temporal behaviour of individual sources. Typically, one of the sources is the latest GRB observed, and the others are taken from the BAT on-board catalog. These data use a FITS lightcurve format to store the multi-channel counts.
• /hk : contains the housekeeping files related to the specific instrument.
• /products : contains all of the high-level products derived from the science files. These are the lightcurves, and spectra of the main source, and the images of the entire FOV. They are provided in FITS format and with their plots as GIF files.

The directory structure for a sequence that includes all of the instruments is the following :

                   /sequence
                      |            
 /auxil   /log   /bat  /uvot   /xrt    /tdrss

With the /bat, /xrt, and /uvot directories beeing further subdivided into :

 
               /bat        
                |  
 /event /survey /pulsar /rate /hk /masktag /products   
 
              /xrt
                |                                           
 /event /image /hk /products   
 
             /uvot
                | 
 /event /image /hk /products

The 'tdrss' and 'trend' directory structure

The data under the sequences in the /tdrss or /trend main directories are not subdivided into directories and therefore data files are directly stored under each /tdrss sequence or /trend type.
As mention above, the sequence directory under the /tdrss main directory contains all the messages sent in response to a trigger. These include messages that result in a good trigger or messages related to false trigger. For false triggers the BAT collects it also contaThe tdrss For the BAT instrument the In addition includes

The messages related to the good triggers are also stored within the science data, /obs directory tree.