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

90 APPENDIX C. BAT ACRONYM AND TERMINOLOGY GLOSSARY
FFT Fast Fourier Transform, used during image reconstruction.
Focal Length In the context of the BAT, “focal length” refers to the distance between the mask
and detector arrays.
FOM Figure of Merit. Refers both to the numerical merit value used to determine whether to slew
to a new GRB or not, and to the on-board software task which computes the merit value.
FOV Field of View, the observable instrumental solid angle.
FTOOLS Software distribution (also known as HEASOFT) which contains the BAT software
tasks.
Gain/Offset Map Detector map produced on-board which contains the coefficients for a linear
pulse-height to energy conversion. A gain/offset map is produced after each calibration pulser
map is constructed, and should be present in each observation data set.
GRB Gamma-Ray Burst.
HK Housekeeping data.
IMX,IMY BAT tangent plane coordinate labels. Equal to X/Z and Y/Z respectively, where
X,Y,Z are the three dimensional coordinates in the instrument reference frame.
IP Image Processor, the flight computer of the BAT.
Malindi Name of the primary ground station which supports Swift.
Malindi Gap Approximate five hour period of each day when there are no possible Malindi ground
station contacts.
Mask The BAT coded aperture consisting of approximately 52,000 lead tiles.
Mask tagged light curves set of light curves generated by the BAT flight software for up to
three sources.
Mask weighting Procedure for generating mathematical weights for each event, to be used to
generated background subtracted light curves, spectra or images. The mask weighting procedure
involves ray tracing.
Maximum rates A special kind of rate history which gives the maximum rate detected on various
timescales. This time series is used in real-time by the flight software for triggering. (also
“max rates”)
Multi-hit A type of diagnostic event which indicates that multiple detectors in a DM Sandwich
were triggered simultaneously, indicating a cosmic ray shower.
Observation ID A unique number assigned to an observation segment. An observation ID has 11
digits. The first 8 digits are the target number, and the last three digits are the observation
segment number.
Observation Segment A group of observing snapshots that are stored in the archive as one data
set, and thus have the same observation ID. Usually an observing segment covers a duration
of less than ∼2 days.
OBSID See Observation ID.