NAME 

       gtpsf - Calculates the effective point spread function, as a
               function of energy at a given source location, averaged
               over an observation.



USAGE
 
       gtpsf expcube outfile irfs ra dec emin emax nenergies thetamax ntheta


DESCRIPTION
       
This tool calculates the effective point spread function, as a
function of energy at a given source location, averaged over an
observation. The theta and psf values are storaged in different
extensions of the output FITS file.  The allowed parameter ranges for
emin, emax, and thetamax (see below) depend on which IRFs you are
using. If you are outside the allowed ranges for a particular set of
IRFs, then the code may (but not definitely) crash.
      


PARAMETERS

    	expcube [file]
          FITS file containing livetime as a function of sky position
          and off-axis angle also referred to as the "exposure
          hypercube file". This file should be generated by gtltcube.
  	  	 
  	outfile [file]
  	 Name of the output FITS file.
  	  	 
  	(outtable = PSF) [string]
          Name of the output file binary table extension which contains the 
          results. This is a hidden parameter. The default value is PSF.
  	  	 
  	irfs [string]
          Instrument response function. 
  	  	 
  	ra [double]
  	  Right Ascension (J2000) of desired source position in
  	  decimal degrees.
  	  	 
  	dec [double]
  	  Declination (J2000) of desired source position in
  	  decimal degrees.
  	  	 
  	emin = 20 [double]
          Minimum of the energy range covered, in MeV. The range of this 
          parameter depends on the response function used. Currently it is  
          recommended that emin be larger or equal to 18 MeV. 
  	  	 
  	emax = 2e5 [double]
          Maximum of the energy range covered, in MeV. The range of this 
          parameter depends on the response function used. Currently it is 
          recommended that emax be smaller or equal to 5.6e6 MeV.
  	  	 
  	nenergies = 20  [int]
  	  Number of logarithmically spaced energies. It should be larger 
          than 1. A typical value could be 20.
  	  	 
  	thetamax = 30 [double]
  	  Maximum angle of apparent photon direction with respect to the 
          source direction (degrees).
  	  	 
  	ntheta = 300 [int]
  	  Number of linearly spaced theta bins.

      (chatter = 2)
          This parameter fixes the output verbosity: no screen output
          (0), nominal screen output (2), maximum verbosity (4). The
          default value is 2. 
  	  	 
     (clobber = yes)        
          Overwrite existing output files. This is a hidden parameter. The 
          default value is: "yes".

     (debug = no)              
          Activate debugging mode. This is a hidden parameter. The
          default value is "no". 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", such exceptions are not caught
          by the top level code. Instead the tool produces a
          segmentation violation, which is more useful for
          debugging. When debugging mode is enabled, the tool produces
          more verbose output describing any errors or exceptions that
          are encountered.

     (gui = no) 
          Graphical user Interface (GUI) mode activated. This is a hidden 
          parameter. The default value is "no".

     (mode = ql)               
          Mode of automatic parameters. This is a hidden parameter. The 
          default value is "ql". 



EXAMPLES
 
Gtpsf handles parameters following the FTOOLs model: They 
can be passed by answering a prompt or as a list in a command 
line. This facilitates calling gtpsf from a script.
 
To be prompted for gtpsf options type in the command line: 
>gtpsf 
 
You will be prompted for the parameter values. Beware that not all 
parameter are prompted: some of the parameter are "hidden".  If you 
want to change one of the "hidden" parameter you should specify the 
values in the command line or modify its mode by editing the parameter 
file. For example if you do not want to overwrite the existing output 
file, type in the command line: 
 
>gtpsf clobber=no  
 
 
An example of how to run the tool is given below: 

> gtpsf 
Livetime cube file[] expCube.fits 
output file name[] psf.fits
Response functions[] P6_V3_DIFFUSE
Source Right Ascension (J2000 degrees) (0:360) [] 193.98
Source Declination (J2000 degrees) (-90:90) [] -5.82
minimum energy (MeV)[20.] 100
maximum energy (MeV)[2e5] 100000
number of energies[20] 
maximum angle (degrees)[30.] 
number of angles[300] 

 
That last example could be also run in the command line as follows: 
 
>gtpsf expcube=expCube.fits outfile=psf.fits irfs=P6_V3_DIFFUSE ra=193.98  
dec=-5.82 emin=100.0  emax=100000.0 nenergies=20 thetamax=30 ntheta=300 




LIST OF BUGS


SEE ALSO 

             gtltcube