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

3.3. NON-GRB PRODUCTS 17
Figure 3.3 shows an example 1 second BAT rate light curve, with a typical background level and
variation for a portion of the orbit. Swift spacecraft orbits which pass near the SAA can produce
BAT rates as high as 10 5 counts per second.
Mask tagged data are generated on-board by the BAT flight software, and contain a crude light
curve of up to three astrophysical sources. These sources are chosen automatically by the flight
software at the time of data collection. The raw mask tagged data may be converted to background
subtracted light curves using the batmasktaglc software task.
3.3.3 Maps
The BAT flight software periodically produces housekeeping maps which are useful for BAT analysis.
The most important of these are detector enable/disable maps and gain/offset maps. Detector
enable/disable maps represent which detectors have been automatically disabled. Usually detectors
are disabled because they are noisy. The number of enabled detectors must be taken into
account when performing mask weighting and image analysis.
Gain/offset maps are produced by the automatic calibration system. They record the approximate
pulse-height-to-energy calibration for each detector. This map, in combination with ground
calibration files, is used to produce calibrated event lists (using bateconvert) and survey files (using
baterebin).
Mask weight maps are associated with mask tagged rates, and are needed to produce background
subtracted light curves. In the standard FITS products, mask weight maps should be
attached to the mask tagged light curve files.
3.3.4 Trend Products
Various other tables and maps are generated as well. These can be broken down into several broad
categories:
• detector maps used in on-board imaging (“scaled” maps);
• calibration pulser maps used to produce gain/offset maps on-board;
• trigger diagnostic tables for rate (long and short) and image trigger systems;
• the on-board source catalog;
• americium tagged-source spectra (“block spectra”) and survey-type data (“Americium DPHs”),
which are used to calibrate the absolute energy scale;
• science housekeeping (“DAP HK”), plus various diagnostics;
• engineering housekeeping;
• debug stream (an ASCII log of the flight software activities);
As noted above, a more detailed description of the format and content of all the products can
be found in Appendix A.