Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.atnf.csiro.au/pub/software/miriad/tutorials/twong.txt Дата изменения: Mon May 19 15:02:26 2003 Дата индексирования: Tue Dec 25 02:29:31 2007 Кодировка: Поисковые слова: http www.badastronomy.com phpbb index.php

Quick and dirty guide for 3mm reduction. In this example, the source is rscl,
the gain calibrator is 0104-408, the bandpass calibrator is 2255-282, and the
flux calibrator is uranus. Contact Tony.Wong@csiro.au to get the data
for this exercise.

*****************
* PRELIMINARIES *
*****************

1. atlod - Read RPFITS file into Miriad

Task: atlod
in=2002-06-21_1746.C1048
out=atfile.1
options=mmrelax,noauto

Sometimes this doesn't work, and you have to repeat the task with
options=mmrelax,noauto,noif.

2. attsys - Applies paddle-derived Tsys values to data
(Only necessary if you disabled Tsys during the observation. The paddle values
have been written to the data file but not applied as yet.)

Task: attsys
vis=atfile.1
out=tcal.1
options=auto [don't apply it if it's already been applied]

3. elevcor - Applies a gain/elevation correction for 3mm
(This is because the antenna gain changes significantly with elevation on
some antennas in a rather predictable way.)

Task: elevcor
vis=tcal.1
out=elevcal.1

4. uvedit - Applies a baseline (relative antennas position) correction
(This is needed because the baselines at 3mm do not seem to be sufficiently
well-determined. Hopefully can be avoided in the future.)

Task: uvedit
vis=elevcal.1
out=uvedit.1
dantpos=2,0.0038,0.0001,-0.0056,4,-0.0025,0.0067,-0.0079 [e.g.]

NOTE: Skip this step during the first reduction pass.

Repeat steps 1-4 for each RPFITS file.

5. List sources and select out those you want to use:
(Repeat for each source and calibrator. Ignore pointing & paddle scans.)

Task: uvindex
vis=elevcal.1 [can repeat for other files]

Task: uvcat
vis="elevcal.*" [or uvedit.*]
select='source(rscl)' [repeat for all calibrators]
options=unflagged
out=rscl

6. Plot UV coverage on source

Task: uvplt
vis=rscl
axis=uc,vc
device=/xw
options=nobase,equal
select='pol(xx)'

7. uvsplit - Split data by frequencies

Task: uvsplit
vis=rscl [repeat for all calibrators]

8. puthd - Specify rest frequency for spectral line (in GHz)

Task: puthd
in=rscl.88638/restfreq
value=88.6318473


****************
* BANDPASS CAL *
****************

All of these steps must be repeated for the 2nd frequency if used.

9. Examine your bandpass calibrator vs. time and vs. frequency:

Task: uvplt
vis=2255-282.88638
axis=time,phase [or time,amp]
device=/xw
size=2,6
yrange=-180,180 [phase only]

Task: uvspec
vis=2255-282.88638
axis=chan,phase [or chan,amp]
interval=1000 [average all data in time]
nxy=1,3
yrange=-180,180 [phase only]

Note the number of edge channels on each end of the spectrum for flagging.

10. Flag edge channels:

Task: uvflag
vis=2255-282.88638
edge=20,16
flagval=f

11. Calibrate the bandpass:

Task: mfcal
vis=2255-282.88638
interval=1000 [average all data in time]
refant=3 [choose a centrally located antenna]

12. Examine the bandpass solution:

Task: gpplt
vis=2255-282.88638
yaxis=phase [or amp]
device=/xw
nxy=1,3
options=bandpass
yrange=-180,180 [or 0,2 for amp]

13. If OK, copy the gains to the other sources:

Task: gpcopy
vis=2255-282.88638
out=rscl.88638 [repeat for gain and flux cal]
options=nocal [do not copy gains vs. time]


*****************
* GAINS VS TIME *
*****************

All of these steps must be repeated for the 2nd frequency if used.

14. Examine phases and amplitudes on gaincal:

Task: uvplt
vis=0104-408.88638
axis=time,phase [or time,amp]
select='pol(xx,yy)'
yrange=-180,180 [for phase]
size=2,6
device=/xw

15. Do the calibration and plot the gains:

Task: mfcal
vis=0104-408.88638
interval=5,2 [average every 5 minutes of cal data]
refant=3 [choose a centrally located antenna]
options=nopassol [don't do passband]

Task: gpplt
vis=0104-408.88638
yaxis=phase [or amp]
nxy=1,3
device=/xw
options=wrap [for phase, don't unwrap]
yrange=-180,180 [for phase]

16. Examine gaincal again with gains applied:

Task: uvplt
vis=0104-408.88638
axis=time,phase [or time,amp]
select='pol(xx,yy)'
yrange=-180,180 [for phase]
size=2,6
device=/xw


*****************
* ABSOLUTE FLUX *
*****************

All of these steps must be repeated for the 2nd frequency if used.

17. Examine amplitudes on flux cal:

Task: uvplt
vis=uranus.88638
axis=time,amp
select='pol(xx,yy)'
device=/xw

18. Rescale the amplitude gains using planet:

Task: plboot
vis=uranus.88638,2255-282.88638,0104-408.88638 [planet,passcal,gaincal]

19. Check the fluxes for our calibrators:

Task: uvflux
vis=2255-282.88638,0104-408.88638


******************
* SOURCE SPECTRA *
******************

20. Apply the gains from the gain calibrator:

Task: gpcopy
vis=0104-408.88638
out=rscl.88638
options=nopass [don't overwrite bandpass gains]

Task: uvcat
vis=rscl.88638
out=rscl.88638.cal

21. Plot the visibility spectrum for each baseline averaged over time:

Task: uvspec
vis=rscl.88638.cal
axis=vel,amp [or vel,phase]
interval=1000
nxy=1,3
device=/xw
yrange=-180,180 [for phase]
select='pol(xx,yy)'


*****************
* MAKE THE MAPS *
*****************

22. Make the dirty map and a postscript plot:

Task: invert
vis=rscl.88638.cal
map=rscl.88638.map
beam=rscl.88638.beam
cell=1 [1" pixels]
imsize=128
sup=0 [natural weighting]
slop=0.5 [don't throw out visibilities with flagged channels]
line=vel,55,-45,1,1
select='pol(xx,yy)'

Task: cgdisp
in=rscl.88638.map
type=c
device=dmaps.ps/ps
labtyp=arcsec
nxy=4,3

23. Do a light CLEAN and plot:

Task: clean
map=rscl.88638.map
beam=rscl.88638.beam
out=rscl.88638.clean
niters=100
region='arc,box(-10,-10,10,10)'

Task: restor
map=rscl.88638.map
beam=rscl.88638.beam
model=rscl.88638.clean
out=rscl.88638.cm

Task: cgdisp
in=rscl.88638.cm
type=c
device=cmaps.ps/ps
labtyp=arcsec
nxy=4,3