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casa
$Rev:20696$
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Public Member Functions | |
| def | __init__ |
| def | __call__ |
Private Attributes | |
| __bases__ | |
| __doc__ | |
Static Private Attributes | |
| string | __name__ |
Definition at line 18 of file widebandpbcor_pg.py.
| def widebandpbcor_pg.widebandpbcor_pg_.__init__ | ( | self | ) |
Definition at line 21 of file widebandpbcor_pg.py.
| def widebandpbcor_pg.widebandpbcor_pg_.__call__ | ( | self, | |
vis = None, |
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imagename = None, |
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nterms = None, |
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threshold = None, |
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action = None, |
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reffreq = None, |
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pbmin = None, |
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field = None, |
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spwlist = None, |
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chanlist = None, |
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weightlist = None, |
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async = None |
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| ) |
Wideband PB-correction on the output of the MS-MFS algorithm
Wide-band Primary-beam correction
(1) Compute a set of Primary Beams at the specified frequencies
(2) Calculate Taylor-coefficient images that represent the PB spectrum
(3) Perform a polynomial division to PB-correct the output Taylor-coefficient
images from the MS-MFS algorithm ( clean(nterms>1) )
(4) Recompute spectral index (and curvature) using the corrected Taylor-coefficient images.
[ Optionally, skip PB-correction, and only recalculate spectral index
with a different threshold ]
This is a temporary task, meant for use until projection-based gridding algorithms
are available via the 'clean' task.
An output directory named imagename.pbcor.workdirectory is created, and filled with
an image-cube of the evaluated primary beams at all specified frequencies,
Taylor-coefficients, and a 'spectral index' due to the primary beam.
Note that for the actual pb-correction, only the Taylor-coefficient images are used.
Task parameters :
vis -- Name of input visibility file
example : vis = 'ngc5921.ms'
Only one MS can be specified here, and it must contain at-least one
timestep of data at all frequencies required to calculate the PB spectrum.
( In case of multiple MSs with different spectral windows, for now,
please split/concat a small fraction of the data to form such an MS )
imagename -- Pre-name of input and output images. Same as in the clean task.
example : imagename = 'run1'
Restored-images ( run1.image.tt0,etc) and residual images ( run1.residual.tt0, etc.. )
must be available on disk.
nterms -- Number of Taylor terms to be used to model the frequency-dependence
of the primary beam.
example : nterms = 2
nterms must be less than or equal to the number of frequencies specified via
spwlist, chanlist and weightlist.
nterms=1 will do a standard division by the average PB computed over all
specified frequencies.
threshold -- Flux level in the restored intensity map, below which to not
recalculate spectral index.
example : threshold = '0.1Jy'
action -- Choice of PB-correction with spectral-index recalculation
or only spectral-index recalculation (using the specified threshold)
example : action='pbcor' or action='calcalpha'
With action='pbcor', the following output images are created/overwritten.
- imagename.pbcor.workdirectory : This directory contains an image cube with
PBs at the list of specified frequencies, and Taylor-coefficient images that
describe the PB spectrum.
- imagename.pb.cube : Concatenated cube of PBs
- imagename.pb.tt0, tt1, ... : Taylor coefficients describing the PB spectrum
- imagename.pb.alpha : Spectral index of the PB (for information only)
- imagename.image.pbcor.tt0,tt1,... : Corrected Taylor coefficients
- imagename.pbcor.image.alpha : Corrected Spectral Index
- imagename.pbcor.image.alpha.error : New error map.
With action='calcalpha', the following output images are created/overwritten
- imagename.image.alpha : Corrected Spectral Index
- imagename.image.alpha.error : New error map.
reffreq -- Reference frequency about which the Taylor-expansion is defined.
example : reffreq = '1.5GHz'
If left unspecified, it is picked from the input restored image.
Note : If reffreq was specified during task clean to produce the images
it must be specified here.
pbmin -- PB gain level below which to not compute Taylor-coefficients or
apply PB-corrections.
example : pbmin = 0.1
field -- Field selection for the Primary Beam calculation.
example : field = '3C291'
This field selection must be identical to that used in 'clean'
spwlist -- List of SPW ids for which to make separate Primary Beams
chanlist -- List of channel ids, within the above SPW ids, at which to make PBs.
example : spwlist=[0,1,2], chanlist=[32,32,32]
Make PBs at frequencies corresponding to channel 32 of
spws 0,1 and 2.
example : spwlist=[0,0,0], chanlist=[0,10,20]
Make PBs at frequencies corresponding to channels 0,10,20
of spw 0
Primary beams are computed at these specified frequencies and
for pointings selected by 'field'. Taylor-coefficients that represent
the PB spectrum are computed from these images.
weightlist -- List of relative weights to apply to the PBs selected via the
spwlist,chanlist parameters. Weights should approximately represent the
sum-of-weights applicable during imaging each of these frequencies.
example : weightlist=[0.5,1.0,1.0]
The first frequency had less usable data due to flagged RFI,
but the other two had relatively equal weight.
These weights are applied to the PB spectrum while computing
PB Taylor-coefficients. Setting weights to anything other than 1.0
makes a difference only with very lop-sided weights. Definition at line 26 of file widebandpbcor_pg.py.
References vla_uvfits_line_sf.verify.
Definition at line 22 of file widebandpbcor_pg.py.
Definition at line 23 of file widebandpbcor_pg.py.
string widebandpbcor_pg.widebandpbcor_pg_.__name__ [static, private] |
Definition at line 19 of file widebandpbcor_pg.py.
1.8.0