12.1.2 How to create a uv Table

uv Tables are created by CLIC using the command TABLE.

A set of commands to create a uv table may look like:

! Reset the default options:
  SET DEFAULT
! find the useful scans:
  FILE IN 21-JAN-1998-H126
  SET SOURCE IRC+10216
  SET RECEIVER 1
  SET PROCEDURE CORRELATION
  SET QUALITY AVERAGE
  FIND
! calibration options:
  SET AMPLITUDE ANTENNA RELATIVE
  SET PHASE ANTENNA RELATIVE INTERNAL ATMOSPHERE
  SET RF ANTENNA ON
! table creation:
  SET SELECTION LINE LSB L01
  TABLE HCN NEW /FREQUENCY HCN  88631.85 /RESAMPLE 19 10 -27 2.12 V

All but the last two commands should be familiar at this point.

• The first new command, SET SELECTION, prepares the last one TABLE. It selects that the next table to be created will be a line table (i.e. with more than one spectral channel). The lower side band data will be used, and only the first subband of the correlator: L01.
• The last command TABLE, actually creates the table named hcn.uvt. The rest frequency, 88631.85 MHz, is set to be the reference used for the velocity scale. The data will be resampled to a velocity grid of 19 channels; the reference channel 10 will correspond to the LSR velocity -27 km/s; the channel spacing will be 2.12 km/s. Without /RESAMPLE, one would have got all the channels in the subband L01 with their original velocity separation. Without /FREQUENCY, the rest frequency present in the data (in the observing procedure) would have been used.

Using /RESAMPLE, one may avoid creating tables with too many channels (by discarding unused parts of correlator subbands) and choose the resolution that is actually needed.

If the data is spread on several files, one may go on by opening the other files, finding the data scans, and appending to the table:

  FILE IN 12-FEB-1998-H126
  FIND
  TABLE
  FILE IN 21-FEB-1998-H126
  FIND
  TABLE
...

(the arguments to TABLE need not to be repeated).

For continuum tables one may use:

SET SELECTION CONTINUUM DSB L01 TO L05 -
  /WINDOW 214405 214726 217476 217796 217837 217875
TABLE CONT-1MM NEW

Here we are using data from all the line subbands, but only in the three frequency windows: 214405 to 214726 MHz, 217476 to 217796MHz, and 217837 to 217875. This is of course to avoid the line emission of some molecules.

A standard menu is available under the CLIC main menu (``Create a UV Table''). After execution, a specific procedure is created to keep track of the options and parameters used. This procedure can subsequently be edited to add new data files (data files can also be added from the menu).

  

Figure 12.1: ``Create a UV Table'' menu in CLIC