Creating UV Tables

UV Tables are just special Tables suited for UV data handling that are created by CLIC. Mapping consists of transforming these tables into something more meaningful for the astronomer, either Images or numbers like positions, flux densities, sizes, etc.

UV Tables are created by CLIC using the TABLE command. The TABLE command offers several options in creating these tables. Four major options should be considered:

1.

Weighting parameters. When the calibration has been carried out correctly, the weights should include both the TSYS correction and the amplitude CALIBRATION factor. Then proper weights are given to every data point, so all analysis programs can estimate errors consistently.

2.

Frequency reference for spectral line observations. The /FREQUENCY option should be used to compute a velocity scale relative to a given spectral line rest frequencies.

3.

/RESAMPLE option should be used when not all channels are required (or when the spectral resolution can be smoothed). /RESAMPLE Nc will select only the first Nc channels of a spectral line subband. /RESAMPLE Nc Ref Val Res Type offers a more general resampling.

To summarize, a CLIC procedure like the following is appropriate to create a table:

SET RECEIVER 1                      ! Select receiver number
SET RF ON FREQUENCY ANTENNA         ! Apply RF passband calibration
SET AMPLITUDE RELATIVE ANTENNA      ! Apply Flux calibration
SET PHASE RELATIVE ANTENNA INTERNAL ! Apply Phase calibration
SET SELECTION LINE USB L01          ! Select the spectral line subband
SET WEIGHT TSYS ON                  ! Apply Tsys correction on noise
SET WEIGHT CAL ON                   ! Apply efficiency correction on noise
FIND/PROC CORR/TYPE O               ! Select Correlation data on Object.
! and create the table...
TABLE Name NEW/FREQUENCY "SiO" 86243.45/RESAMPLE 32

Of course, arguments of the option depend on your particular case. Please refer to the CLIC manual for more details. Note that the frequency is in MHz.