The SWIFT BAT Software Guide Version 6.3 30 ... - HEASARC - Nasa

34 CHAPTER 5. BAT ANALYSIS PROCEDURES
5.4.5 Retrieve Known Problematic Detectors
The BAT team maintains a list of known bad detectors, which is stored in the Calibration Database
(CALDB). These maps only contain detectors (usually detector modules) which were known for
operational reasons to have issues which affect science analysis. The user is still responsible for
filtering the data for noisy detectors (see the next section) or other obvious problems. The ‘batdetmask’
task is used to retrieve the appropriate detector quality map from CALDB.
batdetmask date=total.dpi outfile=master.detmask clobber=YES \
detmask=../hk/swt0142921337bdecb.fits.gz
• date tells batdetmask to retrieve the observation date from the detector plane image you just
created
• outfile is the output master quality map for the observation
• detmask is the detector enable/disable map (usually in the bat/hk directory)
We use the detmask parameter to combine the existing flight enable/disable map with the
quality map based on ground analysis.
5.4.6 Find Noisy Detectors
Noisy detectors are found with the bathotpix task.
bathotpix infile=total.dpi outfile=total.qmap \
detmask=master.detmask clobber=YES
• infile is the detector plane image you just created
• outfile is the resulting quality map
• detmask is the quality map we made in the previous step
5.4.7 Where to Use the Quality Map
The quality map should be used in all subsequent analysis. In particular, it should be used during
the mask weighting process (using the batmaskwtevt task), and in the generation of all light curves
and spectra (using the batbinevt task) and images (using the batfftimage) task. All of these tasks
have an input parameter called detmask= which accept a detector quality map. This information
is used to exclude noisy detectors, and to properly normalize the resulting output fluxes.
5.4.8 The Difference Between the Enable/Disable Map and the Quality Map
There is a difference between the enable/disable map and the quality map we just produced. The
enable/disable map is produced by the flight software, and records which detectors were disabled
at the time. Thus, this map indicates which detectors were noisy in the past, were disabled, and
now have zero counts. The quality map contains that information, but also excludes any currently
noisy detectors, i.e. detectors with too many counts. The BAT flight software does not catch all
noisy detectors. Some detector noise is sporadic, or below the count rate threshold for disabling.
Thus, the best quality map is a combination of both the disabled detectors and the currently noisy
ones.