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Creating a UV Table

You will have first to select which band and subbands are to be used, with command SET SELECTION. The format is

     SET SELECTION key band subbands
`key' may be LINE or CONTINUUM; use CONTINUUM to obtain a table with a single channel, and LINE to obtain a table with multi-channel data. `band' may be USB, LSB, or DSB (the latter is allowed for continuum mode only, and produces two records: one for each sideband). Finally `SUBBANDS' is a group of subbands, like C01 to C06 or L01 to L02, to be averaged in continuum mode, and concatenated in line mode (overlapping spectral bands will cause a resampling to occur).

The table itself will be a file in the Gildas Data Format, of dimensions [ $3 N_C + 7 , N_V$], for $N_C$ channels and $N_V$ visibilities. The $3 N_C
$ lines contain:

  1. U in meters
  2. V in meters
  3. W in meters
  4. Observation date (integer CLASS day number)
  5. Time in seconds since above date
  6. Number of start antenna
  7. First frequency point (real part)
  8. First frequency point (imaginary part)
  9. First frequency point (weight)
  10. Same for second frequency point, and so on

The data weights are controlled by command SET WEIGHTS. SET WEIGHT TSYS ON will turn on weighting by $1/T_{SYS}^2$, and SET WEIGHT CALIBRATION ON will turn on weighting by $1/F_{CAL}^2$, where $F_{CAL}$ is the amplitude instrumental calibration factor (if amplitudes are relative). Both weighting factors may be applied simultaneously. If both factors are OFF, data is weighted proportionally to observing time.

Do not forget to SET PHASE RELATIVE, SET RF ON, and SET AMPLITUDE RELATIVE before you invoke command TABLE, otherwise you will tabulate uncalibrated data. The command TABLE itself should contain the name of the table:
TABLE Name Status [/RESAMPLE nc ref val res code]
where `Status' is NEW to create a new table or OLD to extend an existing one (default). The default and recommended file extension for the UV Table is .UVT.

Option /RESAMPLE resamples the spectrum to a different velocity or frequency resolution, or to select a part of the spectrum only; see internal help for details.


next up previous contents index
Next: Going AIPS Up: Producing Images Previous: Producing Images   Contents   Index
Gildas manager 2018-05-24