Phase Transfer from 230 GHz to 690 GHz

1. Extract phase calibrator and target source

In the example used for this procedure, 1743-038 is the phase calibrator and i1629a is the target source. The multiple source files miriad050218c_230_rx0.lsb.tsys and at 230 GHz miriad050218c_690_rx2.lsb.tsys at 690 GHz have been corrected for system temperature. Using uvsplit, one can extract both the phase calibrator and target source out of the multiple-source files:

uvsplit vis=miriad050218c_230_rx0.lsb.tsys \
        select='source(1743-038,i1629a)' options=nowindow
uvsplit vis=miriad050218c_690_rx2.lsb.tsys \
        select='source(1743-038,i1629a)' options=nowindow

Rename the splitted single source files to convienent file names:

mv i1629a.221381 i1629a.221.lsb.tsys
mv i1629a.682534 i1629a.682.lsb.tsys
mv 1743-038.221381 1743.221.lsb.tsys
mv 1743-038.682534 1743.682.lsb.tsys

Any bad data points must be identified and flagged using smauvplt and uvflag. The flagging must be performed for both files at 221 and 682 GHz so that identical data records are kept in both 221 and 682 GHz files. Make sure that no bad data contaminate both files.

2. Determine the antenna-based phase variation at 230 GHz

Using selfcal with the phase-only option, the antenna-based gain in phase can be solved from the observations of 1743-038 at 221 GHz:

selfcal vis=1743.221.lsb.tsys interval=3 refant=6 line=chan,1,1,768

Using smagpplt, one can check up the gain solution in phase:

smagpplt vis=1743.221.lsb.tsys device=/xs yaxis=phase \
        options=gain polyfit=5 nxy=2,3

If the gain solutions in phase at 221 GHz satisfy you (no bad points such as 90 degree phase jumps), the gain table from the 221 GHz file needs to be copied over to the 682 GHz file using gpcopy in order to create relevant header for the 682 GHz file:

gpcopy vis=1743.221.lsb.tsys out=1743.682.lsb.tsys

3. Transfer 230 GHz phase to 690 GHz

Before do the phase transfer from 230 GHz to 690 GHz, it would be wise to copy over the gain table from 1743.221.lsb.tsys to i1629a.221.lsb.tsys:

gpcopy vis=1743.221.lsb.tsys out=i1629a.221.lsb.tsys
puthd in=i1629a.221.lsb.tsys/interval value=0.25

One may make image of i1629a at 221 GHz to make sure that the selfcal solution in phase derived from 1743-038 at 221 GHz does work for the calibration of the i1629a data at 221 GHz. If the calibrated image of i1629a at 221 GHz did not improve its quality, please go back to find out what is wrong with the gain solutions derived from selfcal. If one is satisfied with the quality of the calibrated i1629a image at 221 GHz, one might continue on the process.

Using phatrans, the phase at 221 GHz from 1743.221.lsb.tsys can be transferred with the antenna-based slopes and phase offsets saved in ceres.682.lsb over to 1743.682.lsb.tsys.

phatrans vis=1743.221.lsb.tsys,ceres.682.lsb,1743.682.lsb.tsys \
        refant=6

Using smagpplt, one may check up the transferred 690 gains in phase:

smagpplt vis=1743.682.lsb.tsys device=/xs yaxis=phase \
        options=gain polyfit=5 nxy=2,3

If the gains in phase look normal, then one might make an image of the calibrator 1743-038 at 682 GHz by applying the transferred gains to the calibrator to make certain that the phase-transfer technique works for the calibrator itself.

If the image of 1743-038 at 682 GHz verifies the phase-transfer successful, one can copy over the gain table to the target source file:

gpcopy vis=1743.682.lsb.tsys out=i1629a.682.lsb.tsys

Using puthd, one may need to reset the interpolation tolerance interval stored in the data header:

puthd in=i1629a.682.lsb.tsys/interval value=0.25

Then, one might proceed to imaging i1629a at 682 GHz using the gains transferred from the calibrator at 230 GHz.