!Novice

    The selections under this menu allow you to store
    various parts of the defined observation in the
    appropriate data base.  It is always safest to use the
    "ALL" selection since this will write the entries in
    the order required by their interconnectivity.  This
    does mean, however, that you must have designed a 
    complete observation, down to the last spectral 
    line and raster description.

!Expert

    If you are an expert user of the system you will realize
    that the four databases involved can be written
    separately.  However, because of the way they are linked
    they must be entered in a specific order viz. Line list,
    data windows, fundamental raster, raster variation (ie
    in the order they appear in the menu).  If you use this
    technique, make sure you know what you are doing, if
    only for the databases' sake!


!Fundamental raster

    A fundamental raster is defined by only 5 parameters.
    They are:

          Detector     (N or G)
          Slit number  (1 to 6)
          Xstep        size of mirror steps in arcseconds 
          Ystep        size of slit steps in arcseconds
          NX           Number of mirror locations in raster
          NY           Number of slit locations in raster

    Each raster defined by a unique combination of these
    parameters is allocated an ID number in the fundamental
    raster database.  Further details of the observation
    performed by this fundamental raster are given in any
    associated raster variation q.v.

!Raster variations

    To allow some flexibility in the definition of 
    observations while minimizing repetition of details,
    each fundamental raster has one or more raster
    variations associated with it.  A raster variation
    is defined by the following parameters:

        Ras_id       the ID of the fundamental raster
                     to which it 'belongs'
        Exptime      the duration (secs) of each exposure
        LL_ID        the unique ID number of the line
                     list to be used in this raster
        Comp_id      the ID of the compression scheme used
        Comp_opt     the option (if any) to be used in the
                     compression scheme
        DW_ID        the unique ID number of the data 
                     extraction window list to be used
        VDS_orient   the readout orientation of the VDS
        VDS_map      the data mapping option of the VDS

    Each raster variation must be a unique combination of
    all these parameters.  If any one changes then a new
    ID must be allocated to the raster variation.

!Line list

    The line list database holds details of the line lists
    (wavelengths) chosen for the observation.  Each line
    list is unique in the number of lines involved and the
    details of the individual lines.  The details of the
    individual lines kept in the database are:

        linename     (character string)
        wavelength   (Angstroms)
        order        (spectral order in which line will
                      be seen)
        position     (in detector pixels)
        waveband     (on detector)

    Clearly some of these are redundant in terms of
    specifying the line.


!Data extraction windows

    The data extraction windows are derived from the
    line list to be used.  They specify the actual 
    pixels that are to be extracted from the detector
    data and so are a combination of the wavelength
    specified and the width (and height for VDS) of
    of the extraction window set.  If DEWs overlap
    in pixel space then they are combined,  Thus
    there can be fewer DEWs than wavelengths in the 
    line list.


       

!State database

    The state database holds information on the setup of the
    instruments which it is anticipated will only change 
    slowly with time.  Currently only the three VDS 
    parameters (read mode, MCP voltage and position offsets)
    are kept in this database.  later some GIS parameters 
    are likely to be entered as well.  Each observation 
    will use whatever setup is indicated as being the 
    latest.  If you choose to edit these parameters and 
    then to store them in the database they will be 
    entered into the database with an operative date and 
    time equal to the UT at which they were stored.
