A PROCEDURE OF HIGH SPECTRAL RESOLUTION DATA REDUCTION

A procedure of handling very high spectral resolution data has been discussed in an SMA Miriad memo . The part of procedure in data loading, data inspection, corrections for system temperature should be identical to that used for handling normal resolution data. A special attention may need to take in handling bandpass and antenna gain calibrations. Assuming that 060512_rx0.lsb.tsys is the lower side band data with corrections for system temperature, the calibration part of the procedure is highlighted below:

1. Data Separation

Before executing the calibration tasks, the high (chunk 16) and low (1,2,3,4,5,6,7,8,9,10,11,12) spectral data are separated into two working files, 060512_rx0.lsb.tsys.hr and 060512_rx0.lsb.tsys.lr:

uvaver vis=060512_rx0.lsb.tsys select='window(1,2,3,4,5,6,7,8,9,10,11,12)' \
        options=nocal out=060512_rx0.lsb.tsys.lr
uvaver vis=060512_rx0.lsb.tsys select='window(16)' \
        options=nocal out=060512_rx0.lsb.tsys.hr

2. Bandpass Calibration

Then, we solve for the antenna-based bandpass:

smamfcal vis=060512_rx0.lsb.tsys.lr select='source(neptune)' edge=3,3   \
         refant=3 interval=600
smamfcal vis=060512_rx0.lsb.tsys.hr select='source(neptune)'   \
         weight=2 refant=3 interval=600 smooth=7,1,0.9 options=msmooth

Note that a moving smoothing is performed prior to solving for the antenna-based bandpass in order to improve the signal for the high spectral resolution data. Please check up the bandpass solutions:

 
smagpplt vis=060512_rx0.lsb.tsys.lr  device=/xs \
        yaxis=amp,phase \
        options=bandpass  polyfit=5 \
        nxy=2,4

smagpplt vis=060512_rx0.lsb.tsys.hr  device=/xs \
        yaxis=amp,phase \
        options=bandpass  polyfit=5 \
        nxy=2,4

If the solutions are satisfying, then they can be applied to the data:

uvaver  vis=060512_rx0.lsb.tsys.lr options=nocal \
        out=060512_rx0.lsb.tsys.lr.bp
uvaver  vis=060512_rx0.lsb.tsys.hr options=nocal \
        out=060512_rx0.lsb.tsys.hr.bp

3. Antenna Gain Calibration

The phase reference source (0133+476) can be split from the lower-spectral-resolution multiple source file that has been applied with bandpass corrections :

uvsplit vis=060512_rx0.lsb.tsys.lr.bp     \
        select='source(0133+476)' options=nowindow
mv  0133+476.216816 0133+476.lsb.tsys.lr.bp     % rename the file

Then we solve for antenna-based gain (phase-only):

selfcal vis=0133+476.lsb.tsys.lr.bp \
refant=5 interval=.5 options=pha

One may check up the gain solutions. If the solutions are good, then the gain table can be copied over to both the high and low spectral resolution data files:

gpcopy vis=0133+476.lsb.tsys.lr.bp out=060512_rx0.lsb.tsys.lr.bp \
        mode=copy options=nopass
gpcopy vis=0133+476.lsb.tsys.lr.bp out=060512_rx0.lsb.tsys.hr.bp \
        mode=copy options=nopass
% reset the solution interpreation tolerance to a long time interval
puthd in=060512_rx0.lsb.tsys.lr.bp/interval value=600 type=double
puthd in=060512_rx0.lsb.tsys.hr.bp/interval value=600 type=double

One could apply the gain solutions to the data or leave the gain table in the data files and apply them while executing relevant tasks. To this point, the calibration for bandpass and antenna gains are completed.