Data Products

1
Data Products

• David Band and a cast of thousands

2
Data Products Used by SAE

• Here we discuss the data products (DPs) that
  result from Level 1 processing (reconstruction
  for the LAT, calibration for the GBM) and will be
  used by Level 2 data analysis (e.g., fitting
  spectral models).
• These are the DPs that will be provided to the
  general scientific community, and will be the
  beginning for almost all astrophysical data
  analysis.
• These DPs are FITS files. FITS files consist of
  a series of units, each with an ASCII header
  and a binary data table. FITS files can be read
  by the tool fv.
• Only some of the DPs will be necessary in DC2.

3
Science Data Products ICD

• The files are defined by the Science Data
  Products ICD glast.gsfc.nasa.gov/ssc/dev/current
  _documents/Science_DP_ICD.doc
• The development status of all the DPs is
  summarized at glast.gsfc.nasa.gov/ssc/dev/data_pro
  ducts/science_data_products.html which includes
  links to sample files.
• The file names provide the DP type, detector,
  version number, time or burst name, etc. For
  example
• GLG_TTE_N4_BN070509400_V01.FIT
• Note an Operations Data Products ICD
  (timelines, Level 0 data) has been baselined and
  is maintained by the MOC.

FITS file
GLAST DP
GBM
Version number
Time-Tagged Events
Burst name
NaI detector 4
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The LATs Photon DPs

• Most of the LAT tools operate on photon files
  (called FT1)lists of LAT photonsand their
  auxiliary pointing/time history files (called
  FT2).
• FT1 and FT2 files are extracted from GSSC or
  LISOC databases for a specific analysis. Further
  selections can be made (toolgtselect).
• FT1 files are subsets of event files and contain
  information (arrival time, apparent energy,
  direction, etc.) required by the analysis tools
  for events identified as photons
• The FT1 files include the criteria used to select
  the photons (e.g., region, energy).
• Additional information for each event can be
  found in the event files (called FT0).
• The pulsar tools add information to the FT1
  files.
• FT2 files provide GLASTs position, orientation,
  and livetime every 30 seconds.

5
Other LAT Files

• The Instrument Response Functions (IRFs) will be
  in files stored in a CALDB file system. The SAE
  knows how to access these files, and therefore
  the average investigator need not.
• Catalog files
• Pulsar ephemerides

6
GBM DPsDaily Data

• The GBM will produce burst and non-burst DPs.
• The daily versions of the continuous DPs provide
  the binned count rates from the 12 NaI and 2 BGO
  detectors, whether or not a burst has been
  detected.
  
• CTIME 8 energy channels every 0.256 s
  
• CSPEC 128 energy channels every 8.192 s
• For DC2 we are providing CTIME and CSPEC for the
  detectors facing the burst, with at most one
  burst per file.
• There are no tools that use these data.
• There are also housekeeping, calibration and
  catalog files that during the mission will be
  produced on various timescales, but are not being
  provided for DC2.

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GBM DPsBurst Data

• The GIOC will provide a number of burst-related
  DPs.
• Time-tagged events (TTE)a list of counts from
  the burst
• During the mission TTE data from all detectors,
  one file per detector, will be provided
• All detectors because the spacecraft may slew
  during a burst
• For DC2 we are providing TTE files only for the
  burst-facing detectors
• The counts are in one of 128 energy bins
• CTIME and CSPECburst versions of the daily DPs
• Rates from 4000 s before to 4000 s after the
  trigger
• Again, during the mission all detectors will be
  included
• For DC2 only the burst-facing detectors will be
  provided
• Again, these data are not used by any tool

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GBM DPsAuxiliary Burst Files

• Detector Response Matrices (DRMs)the mapping
  between the input spectrum and the binned count
  spectrum.
• During the mission the GIOC will provide an RSPII
  file for each detector with multiple DRMs per
  file
• For DC2 simple RSP files with one DRM per file
• During the mission the SAE will include a tool
  for users to calculate their own DRM file
• Backgroundthe background rate for each detector
  in 128 energy bins
• During the mission the background file will also
  include a polynomial model of the background
• For DC2 a constant background is assumed
• During the mission users will be able to
  calculate their own background file

9
Binned GBM Spectral Analysis

• Note that for DC2 you will be provided with
• Unbinned (in time) burst counts
• DRMs
• Background spectra
• Using the binning tool (gtbin) you can produce
  binned burst spectra (i.e., PHA files)
• You now have all the ingredients for XSPEC-style
  spectral analysis.

10
GBM DPsTRIGDAT

• When the GBM or the LAT detects a burst, it will
  telemeter data to the ground through TDRSS.
• These TRIGDAT messages provide
• Burst localization
• Lightcurves
• Background rates
• Whether an autonomous repoint was recommended
• The GIOC will package the GBMs TRIGDAT messages
  into a FITS file and provide it with the other
  burst data
• Some simulated GBM TRIGDAT messages will be
  provided in DC2.