Adding a new mission to XIMAGE
------------------------------

1. Read in file with read_image command

2. Run chheader/show

   The internal header values that are "safe" to change will be printed.
   All internal header values may be viewed with the syntax,
   chheader all

3. To modify values, chheader/key=KEYWORD/val=VALUE

   Required keyword updates:

      TELESCOP  /  If this is blank, set the telescope name
      INSTRUME  /  If this is blank, set the instrument name

   Optional keyword updates:

     Some missions may use a third keyword for identification

      DETNAM    /  Set to detector name if necessary

     For sky coordinates to appear properly

      CTYPE1    /  Set to RA--TAN if sky coordinates are available
      CTYPE2    /  Set to DEC-TAN if sky coordinates are available
      CRVAL1    /  Set to the RA value of CRPIX1
      CRVAL2    /  Set to the Dec value of CRPIX2
      EQUINOX   /  Set to equinox of CRVAL1/2
      CDELT1    /  Set to x pixel size in degrees
      CDELT2    /  Set to y pixel size in degrees

     For detector coordinates to appear properly

      ZMX       /  Set to zoom factor w.r.t. original x coords (def=1)
      ZMY       /  Set to zoom factor w.r.t. original y coords (def=1)
      DRPIX1    /  Set to x center in original coords     (def=CRPIX1)
      DRPIX2    /  Set to y center in original coords     (def=CRPIX2)

      Note: If CTYPE originally referred to a flat (original detector)
      coordinate system, the values reported as CRVAL correspond
      to what DRPIX should be.

      Also, after changing the coordinate system, it is necessary
      that you redisplay the image if it is already being displayed.
      Otherwise, subsequent commands will be working under the new
      coordinates, while the PGPLOT device will be set to the old
      coordinates.

     For labeling image

      OBJECT    /  Set to field name

     For rates to appear properly

      EXPOSURE  /  Set to the total exposure time   (def=1000.)
      DTIME     /  Set dead time correction         (def=1.0)

4. Create a psf file using the psf command with the calfile qualifier.
   The center and radius may be specified through the cursor or the x,
   y, and radius qualifiers.  (e.g. PSF/CALFILE/CUR) Note: The radius
   qualifier will be in arcmin if CTYPE reflects sky coordinates,
   otherwise it will be in pixels. The new PSF file will be named:
   ximage_psf.dat Rename the file to something appropriate.

   It is possible to create a PSF file based on multiple sources.
   Using the multpsf qualifier to specify the output file.  For 
   each time PSF is run, a new column will be appended to the 
   existing calfile.

6. Update the mission database (mdb):

    The mdb contains various parameters for specific telescope/instrument
    combinations.  When adding a new mission, it may be easiest to find a
    mission that has similar properties, and modify that.  Internally
    one can use the syntax:
    
      chmdb/copy/tel=OLD_TEL/inst=OLD_INST/totel=NEW_TEL/toinst=NEW_INST

    One can also start a new mission from scratch, using the following:

      chmdb/add/tel=NEW_TEL/inst=NEW_INST

    Now, one can update the PSFFILE keyword to reflect the name of 
    the newly created psf file:

      chmdb/tel=NEW_TEL/inst=NEW_INST/key=PSFFILE/val=mypsf.dat

    If the loaded image has TELESCOP and INSTRUME defined, you
    may omit them in the specification of the chmdb command, as
    they will be assumed.

      chmdb/key=PSFFILE/val=mypsf.dat

    However, if many mdb keywords must be changed, the suggested
    method is to write out the mdb to a file, edit the file, and
    read it back in.

    To write the entire mdb:

      chmdb/output=myfile.mdb

    Or just a specific telescope/instrument combination:

      chmdb/tel=NEW_TEL/inst=NEW_INST/output=myfile.mdb

    Edit the PSFFILE entry for the new mission and any other
    keywords that need modification. Then, read it back in with:

      chmdb/input=myfile.mdb

7. Run the psf command again as a test:

    psf/x=XVAL/y=YVAL/radius=RVAL

    If you use the same values as in (4.) above, the solid line
    should overlay the individual points exactly.

    Note: The PSF values in the output plot reflect an assumed exposure
    time of 1000 seconds if the EXPOSURE key wasn't in the FITS file
    and it hasn't been updated internally.

8. Run the detect command:

    The background and source box values may need some tweaking for
    the unknown mission.  Particularly, if you see 'Local background
    not well estimated' messages, the background box should be set
    to a lower value.

    detect/back_box_size=BACKBOX/source_box_size=SRCBOX

Note:

   To make these changes part of your ximage distribution, the mission
   must be added to the ximage.mdb file in the manager directory, and
   the generated psf file copied under the cal directory.  A directory
   inside the cal directory must be created named for the telescope, and
   inside that a directory named for the instrument.  The psf file should
   be copied to the instrument directory and be named of the form
   psf_instrument.dat, or if detector name is important for the mission, 
   use the form psf_detnam.dat.