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FERMIGDAYS - Fermi GBM Daily Data



The Fermi GBM Daily Data database table contains entries for each day for which GBM data has been processed.

The daily data products consist of GBM data that are produced continuously regardless of whether a burst occurred. Thus these products are the count rates from all detectors, the monitoring of the detector calibrations (e.g., the position of the 511 keV line), and the spacecraft position and orientation.

Some days may also have event lists known as time-tagged event (TTE) files associated with them. These TTE files have the same format as those produced for bursts. Due to the large data volume associated with TTE files, only certain portions of the day considered of scientific interest to the instrument team will have TTE data.

The underlying Level 0 data arrive continuously with each Ku band downlink. However, the GBM Instrument Operations Center (GIOC) will form FITS files of the resulting Level 1 data covering an entire calendar day (UTC); these daily files are then sent to the FSSC. Consequently, the data latency is about one day: the first bit from the beginning of a calendar day may arrive a few hours after the day began while the last bit will be processed and added to the data product file a few hours after the day ended. These data products may be sent to the GSSC file by file as they are produced, not necessarily in one package for a given day.

Note that the data may include events from slightly before and slightly after the day official boundaries, which will be reflected in the start and stop times in the table. Consequently, some events may be listed in files for two consecutive days (e.g., at the end of one and the beginning of the next).

Due to the continuous nature of GBM processing, new data files may arrive after the day has been included in Browse and reprocessed version may also arrive at any time. The reprocessed data will have the version number incremented (see file name conventions below). Browse will automatically download the latest versions of the data files.


The FERMIGDAYS database table was last updated on 17 April 2014.


Please see the warnings on the GBM Caveats page,


See the Fermi Science Data Products Interface Control Document (GLAST-GS-ICD-0006;


This database table was created by and is updated by the HEASARC based on information supplied by the Fermi Project. It is updated on a daily basis. The tte_flag parameter was added to the table in July 2010.


The MJD (Modified Julian Date) day number for each day for which GBM data has been processed.

The start time of the data for the specified day number, in UTC.

The stop time of the data for the specified day number, in UTC.

The unique day identification in YYYYMMDD format.

This field contains a boolean flag (values 'Y' or 'N') which indicates whether or not time-tagged event (TTE) data is available for the specified day.

Contact Person

Questions regarding the FERMIGDAYS database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 16-Apr-2013