EXOMERGE (sep98)             ftools.exomerge            EXOMERGE (sep98)



NAME
    exomerge -- merge compatible EXOSAT LE event files
    
    
USAGE
    exomerge @evtlist outfile
    
    
DESCRIPTION
       This task merges event files obtained from a  single  observation
    with  the     EXOSAT  CMA  detector  and  it  corrects the reference
    coordinates if    data were taken with the star tracking mode  STR1.
       It  is  intended  to work for EXOSAT CMA raw data files as stored
    in  the     HEASARC  archive.  The  content  for  each   observation 
    includes  a  catalog  file,     an  orbit file and several event and
    housekeeing  files.  Within  an     observation,  a  new  event  and 
    housekeeping  file  was  created  either  after  a     few  hours of
    observing time (ranging between 2-4 hr) or because of changes     in
    one  or  more observational parameters.     The task checks that all
    the input event  files  share  the  following  modal     parameters:
    pointing  mode  (STAR_PNT),  detector  (INSTRUMENT),  energy  filter 
       (FILTER), on board computer mode (OBCMODE), and the same  grating
    setting     (GRATING).  An  error  is  reported for any of the above
    modal parameter    differences found. The task will  stop  execution
    and  no  merged  file  is     created. Before restarting the process
    discard in the list of input event     files  those  with  different
    modal  parameters.      A warning instead is given, if the data were
    taken with different background    filters,  known  as  the  diamond
    filter.  This  filter  masks part of the    detector FOV. The merged
    event file is created but it is usable only     within  the  diamond
    region  (e.g.  outside  the  exposure  will  be     underestimated). 
       The 'exomerge' output file will have all the  extensions  merged,
    the data    sorted in time and the timing header keywords updated.
    
       EXOSAT  could  be  programmed to maintain the spacecraft attitude
    in two    modes, start tracking mode 1 (STR1) and 2 (STR2). In  STR1
    the  spacecraft     attitude  was  maintained  using one star in the
    star tracker field of    view (FOV) and  the  position  of  the  sun
    determined  using  the  fine  sun    sensor (FSS). STR2 instead used
    two stars in the star tracker FOV.     In STR1 mode a correction  to
    the  reference  coordinates  is  needed  to     account for the roll
    error in the spacecraft attitude.  The  correction     modifies  the
    RA_NOM,  DEC_NOM,  TCRVL2,  TCRVL3, TROTA3 and TCROT3 keywords    in
    the merged event file. This is calculated using  routines  from  the
       EXOSAT  Interactive Analysis software package and the information
    stored    in the housekeeping and orbit files. The calculation  uses
    the  housekeeping     values  corresponding  to  the midpoint of the
    time interval between the first    and the last input event file.  A
    warning  is  given if there are no    housekeeping data available at
    the midpoint observation time (e.g. for  a     data  gap).  In  this
    case  the  correction  is based on the housekeeping values    at the
    closer midpoint time.
    
       Exomerge can be run standalone or  using  two  different  scripts
       which  create  the  input  list  for  exomerge  and run exomerge.
       The first, tkexomerge, is a graphic user interface  using  Tcl/TK
       which  displays  the  content  of the catalog file and allows the
    user    to create the input list by mouse selecting the event  files
    to  merge.      The other, automerge, is a perl script which creates
    a list of event files     on  the  user  response  to  a  few  input
    paramaters (e.g.detector, filter type,    and the grating setting).
    
    
    
PARAMETERS
    
    evtfile [string]
        Filename  of  the  ASCII file containing the list of event files
        to be merged.
    
    outfile [string]
        Output filename for the the merged event file.
    
    tchat (terminal chattiness) [integer]
        Set terminal chattiness.
    
    lchat (log file chattiness) [integer]
        Set log file and chattiness in the log file: = 0  the  log  file
        is not written.
        
        clobber (overwrite output file if it exists?) [yes/no]
            Allows or prevents output file from being overwritten.
        
        
EXAMPLES
        Create a merged event file, out.evt, using the event files listed in the 
        file evtlist.
    
       > exomerge evtfile=@evtlist outfile=out.evt 
    
    
SEE ALSO
    tkexomerge, automerge