1 UV_SHORT Compute short spacing visibilities from a single‐dish spectra table
        UV_SHORT

    Warning:    It   is   advised   to  use  this task  through  the  "Short
    Space Processing" widget available in the MAPPING main menu.

    This  task prepares  the UV  tables  of   the  missing   short  spacings
    from a single‐dish table  of spectra  (the table format  is described in
    the GRID command of CLASS).  This table  should later be merged  to  the
    corresponding interferometer UV table.  Two major steps are performed:

      ‐ Creation of a "well behaved" map from the spectra.
      ‐ Extraction of UV visibilities from this map.

    It  is  advised  that  the  input  table is a collection of single‐dish,
    Nyquist sampled  spectra  covering  twice   the   interferometric  field
    of  view  of interest. However, this  tasks does *not* make any  assump‐
    tion. It thus try to compute  a "well behaved"  map by linear operations
    (convolutions)  from  the   original  spectra,  in an  optimum way  from
    signal  to noise  point of view. The  map is  extrapolated smoothly  to‐
    wards  zero at  the map  edge in order  to  avoid  further  aliasing  in
    the  Fourier  transform  operations required in  step 2.  This  extrapo‐
    lation   has a scale  length of  twice the single‐dish beam, in order to
    avoid spurious Fourier components.

    In detail, UV_SHORT performs the following operations:

      ‐ Resampling  (in space) of  the original  spectra on  a regular  grid by
        convolution  with  a small  (typically  1/4  of  the single‐dish  beam)
        gaussian convolving kernel. In  this process, the weights of individual
        spectra is carried on a weight map.
      ‐ Extrapolation by  zero outside  the convex hull  of the  mapped region.
      ‐ Convolution  of  the  result  by  a  gaussian  twice  as  wide  as  the
      ‐ single‐dish beam.   Within the  convex hull of  the mapped  region, the
      ‐ smoothed map is replaced by the original map.

    From  this map,  UV_SHORT  computes the  needed   UV  tables   (one  for
    each pointing center in case of a mosaic) in the following way:

      ‐ Fourier transform of the single dish map;
      ‐ Division by  the Fourier  transform of  the single dish  beam, up  to a
        maximum spacing (SD_DIAM$, in meters);
      ‐ Inverse Fourier transform to the image plane and then for each pointing
        center;
      ‐ Multiplication of the  image by the primary beam  of the interferometer
        elements;
      ‐ Fourier transform back to the UV plane;
      ‐ Creation  of the  UV  table, with  a  given weight  SD_WEIGTH$ and  an
        appropriate calibration factor to Janskys SD_FACTOR$

    Both  the   single‐dish and the  interferometer antennas are assumed  to
    have gaussian beams (SD_BEAM$ and IP_BEAM$, in radians).

2 TABLE$
        TASK\CHARACTER "Input TABLE name" TABLE$

    The table of spectra in the format described  in  the  GRID  command  of
    CLASS  command. The easiest way to produce it is by using the CLASS GRID
    command!

2 UV_TABLE$
        TASK\FILE "UV table" UV_TABLE$

    Generic output UV table name, without  extension.  When  the  number  of
    fields  NF$ is larger than 1, UV_SHORT will add ‐’I’ to the generic name
    to create a UV table for field I.

2 MAP$
        TASK\CHARACTER "Output MAP name" MAP$

    The name of the single dish "well behaved" map which  will  be  produced
    (as an intermediate result] by UV_SHORT.

2 XCOL$
        TASK\INTEGER "Column of X coordinates" XCOL$ 1

    The  column  of  the spectra table containing X offsets. For tables pro‐
    duced by GRID command of CLASS, XCOL$ should be 1.

2 YCOL$
        TASK\INTEGER "Column of Y coordinates" YCOL$ 2

    The column of the spectra table containing Y offsets.  For  tables  pro‐
    duced by GRID command of CLASS, XCOL$ should be 2.

2 WCOL$
        TASK\INTEGER "Column for weights" WCOL$ 3

    The  column of the spectra table containing the weights. For tables pro‐
    duced by GRID command of CLASS, XCOL$ should be 3.

2 MCOL$
        TASK\INTEGER "First and last column to grid" MCOL$[2] 4 0

    The first and last column to be mapped. For tables produced by GRID com‐
    mand  of  CLASS,  MCOL$[1]  should  be 4 and MCOL$[2] can be set to 0 to
    process all channels.

2 WEIGHT_MODE$
        TASK\CHARACTER  "Gridding   Mode   (GRid,   NAtural   or   UNiform]"
    WEIGHT_MODE$ "UN"

    The weighting mode. It is advised to use ’NA’ for Natural weighting.

2 TOLE$
        TASK\REAL "X‐Y position tolerance" TOLE$ 1*SEC

    The  tolerance  in  position. Spectra differing by less than this amount
    will be added together prior to gridding.

2 MIN_WEIGHT$
        TASK\REAL "Minimum weight"  MIN_WEIGHT$ 0.01

    The minimum weights under which a given  point  in  the  map  should  be
    filled by the smooth map rather than by the gridded (original] map.  De‐
    fault value of 0.01 is appropriate.

2 SD_BEAM$
        TASK\REAL "Single dish beam diameter [radians]" SD_BEAM$

    Half‐power beam width of the single dish antenna, in radians.  The  beam
    is assumed to be gaussian.

2 SD_DIAM$
        TASK\REAL "Single dish diameter [m]" SD_DIAM$ 30.0

    Single  dish  diameter used to produce the input spectra. Value for Pico
    Veleta is 30m.

2 IP_BEAM$
        TASK\REAL "Interferometer primary beam [radians]" IP_BEAM$

    Half‐power beam width of the interferometer antennas, in   radians.  The
    beam is assumed to be gaussian.

2 IP_DIAM$
        TASK\REAL "Interferometer diameter [m]" IP_DIAM$ 15.0

    Interferometer diameter for which UV_SHORT will produce short space vis‐
    ibilities. Value for Bure is 15m.

2 UV_TRUNC$
        TASK\REAL "UV truncation radius [m]" UV_TRUNC$ 15.0

    No visibilities at spacing higher than UV_TRUNC$ is generated. Theoreti‐
    cal consideration on the method used in this task implies that UV_TRUNC$
    should be at most  (SD_DIAM$‐IP_DIAM$).  For  combination  between  Pico
    Veleta and Bure, UV_TRUNC$ is 15m.

2 DO_SINGLE$
        TASK\LOGICAL "Do single dish deconvolution" DO_SINGLE$ YES

    Logical value, should be YES except for test purposes.

2 DO_PRIMARY$
        TASK\LOGICAL "Do primary beam product" DO_PRIMARY$ YES

    Logical value, should be YES except for test purposes.

2 SD_WEIGHT$
        TASK\REAL "Single dish Weight factor" SD_WEIGHT$ 1

    Total weight of the generated visibilities.  If set to 0, it will be set
    to 10**‐6/sigma**2, where sigma is the RMS  of  the  zero‐spacing  value
    (total flux) in janskys.

2 SD_FACTOR$
        TASK\REAL "Single dish calibration factor" SD_FACTOR$ 5.9

    Multiplicative calibration factor; it is used to convert from the single
    dish map units (e.g., main‐beam brightness temperature) to janskys.

2 MOSAIC_RA$
        TASK\CHARACTER "Center of mosaic: R.A." MOSAIC_RA$

    The Right Ascension (HH:mm:ss.sss) of the center of  the  interferometer
    field  (i.e. center of the mosaic or pointing center of the interferome‐
    ter for a single field).

2 MOSAIC_DEC$
        TASK\CHARACTER "Center of mosaic: Dec." MOSAIC_DEC$

    The Declination (Sdd:mm:ss.sss) of  the  center  of  the  interferometer
    field  (i.e. center of the mosaic or pointing center of the interferome‐
    ter for a single field).

2 NF$
        TASK\INTEGER "Number of fields" NF$

    Number of fields to be created. NF$ should be equal  to  the  number  of
    fields  used  in the mosaic at the interferometer. NF$ is 1 for a normal
    observation.

2 RA$
        TASK\REAL "Offsets of fields in X (RA) [radians]"  RA$[NF$]

    Projected offsets on the sky of  the  pointing  centers  of  the  mosaic
    fields  parallel to the right ascension axis, with respect to the mosaic
    center defined by MOSAIC_RA$ and MOSAIC_DEC$.

2 DEC$
        TASK\REAL "Offsets of fields in Y (Dec) [radians]" DEC$[NF$]

    Projected offsets on the sky of  the  pointing  centers  of  the  mosaic
    fields parallel to the declination axis, with respect to the mosaic cen‐
    ter defined by MOSAIC_RA$ and MOSAIC_DEC$.

1 ENDOFHELP
























































