gtltcube

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Synopsis:

Calculates the integrated livetime as a function of sky position and off-axis angle.

Using the spacecraft data file and the time range and GTI selections in the event file, this tool integrates the livetime as a function of sky position and off-axis angle. The sky is represented using a nested HEALPix array.

Usage: gtltcube evfile scfile outfile dcostheta binsz

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General Parameters

  evfile [file]
   

Event data file.

If several events files have to be input (event files which cover different time intervals), an ASCII file with a complete list should be entered here with an "@" sign before the name. For example, if the name of that ASCII file is "event_files", enter this parameter as: evfile=@event_files.
     
  (evtable = EVENTS) [string]
    Event table extension name. (default: EVENTS)
     
  scfile [file]
   

Spacecraft data file.

Contains information such as the spacecraft pointing as a function of time. For simulated observations, this file can be generated by gtorbsim, and for real observations, it can be obtained from the SLAC Data Portal.
     
  (sctable = SC_DATA) [string]
    Spacecraft data extension.
     
  outfile [file]
    Output FITS file name.
     
  dcostheta = 0.025 [double]
    Inclination angle binning represented as the cosine of the off-axis angle.
     
  binsz = 1 [double]
    Pixel size of the desired spatial grid in degrees.
     
  (phibins = 0)
    Number of phi bins. When phibins=0, the phi-integrated livetimes are computed, and in subsequent exposure calculations, (e.g., with gtexpmap or gtexpcube2), the phi-averaged effective area is used. For normal survey mode observations and for time scales longer than 12 hours, the variation of the exposure induced by the phi-dependence of the effective area is <3%. Because of the square shape of the LAT, the phi-dependence has an 8-fold symmetry and has an RMS variation of <10% at 100 MeV. A value of phibins=5 is usually sufficient to capture the phi-dependence on time scales shorter than 12 hours.
     
  (tmin = 0) [double]
   

Minimum time (MET s).

MET (Mission Elapsed Time) is the number of seconds since midnight (00:00:00) January 01, 2001 Coordinated Universal Time (UTC).

  • tmin and tmax apply only if evfile is a null string.
  • If tmin is less than the TSTART time in the event file, then tmin=TSTART is used.
  • To see the filters applied to the time range, set the chatter parameter to "chatter = 4".
     
  (tmax = 0) [double]
   

Maximum time (MET s).

  • If tmax is greater than the TSTOP time in the event file, then tmin=TSTOP is used.
     
  (file_version = 1) [string]
   

Version of output file.

Sets the value of the VERSION keyword in the primary header of the output file.
     
  (zmax = 180) [double]
   

Maximum zenith angle.

The maximum zenith angle over which the livetimes are integrated. This zenith angle selection pertains to true source locations on the sky. Therefore this cut is not equivalent to applying a maximum zenith angle cut in gtselect, since in the latter case the cut is made on measured photon directions. Non-default zenith angle selection should not be used for standard analyses.
     
  (chatter = 2)
    This parameter fixes the output verbosity: no screen output (0), nominal screen output (2), maximum verbosity (4).
     
 
(clobber = yes)
    If yes, an existing file of the same name will be overwritten.
     
  (debug = no)
   

Activate debugging mode.

When debug is "no", all exceptions that are not caught and handled by individual tool-specific code are caught by a top-level exception handler that displays information about the exception and then exits. When debug is "yes", these exceptions are not caught, and the code is allowed to fail where the exception was thrown. This option is intended to be used while running the code under a debugger.

     
  (gui = no)
    If the parameter specified is "yes", the Graphical User Interface (GUI) mode is activated.
     
  (mode = ql)
    Mode of automatic parameters.