1934 at 11GHz

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1934 at 11GHz

Postby tg1989 » Mon May 18, 2015 6:31 pm

Hi all,

I have some data centered at 10.8 GHz that I am trying to calibrate. My bandpass and flux calibrator is 1934 and so far I have had no luck getting a meaningful calibration.

I have done an initial mfcal/gpcal using fairly typical parameters, and the solutions seem to converge. I have used two different intervals between the mfcal/gpcal below, so the number of solution intervals are different. This is simply because they were the first I found in my terminal scroll back.

Code: Select all
MfCal: $Revision: 1.16 $, $Date: 2014/04/29 00:50:17 $
Selecting parallel-hand polarisations
Reading the data ...
### Warning:  Correlations flagged or edge-rejected: 771120
### Warning:  Number correlations lacking minant/refant: 109980
Number correlations accepted: 6433830
Number of frequency bands/settings: 1
Number of polarisations selected: 2
Number of solution intervals: 117
Number of passband solution intervals: 1
Initialising ...
### Warning:  Using post-Aug94 ATCA flux scale for 1934-638
Using known frequency variation of 1934-638
Generating initial solution estimate ...
Doing solution refinement ...
tIter= 1, Solution Error:  0.685
get uvIter= 2, Solution Error:  0.019
pltIter= 3, Solution Error:  0.000
Saving solution ...


Code: Select all
gpcal: Revision 1.19, 2014/04/28 01:00:33 UTC

Applying bandpass corrections to 1934-638.10800/
Number of antennae: 6
Reading the data ...
Number of solution intervals: 69
Total visibilities read: 1035
Number visibilities accepted: 1035
Using post-Aug94 ATCA flux scale for 1934-638.
Using IQUV =  2.1590,  0.0000,  0.0000,  0.0000 at  10.7872 GHz.
Using post-Aug94 ATCA flux scale for 1934-638.
Using IQUV =  2.3458,  0.0000,  0.0000,  0.0000 at  10.0822 GHz.
Using post-Aug94 ATCA flux scale for 1934-638.
Using IQUV =  2.2203,  0.0000,  0.0000,  0.0000 at  10.5432 GHz.
Using post-Aug94 ATCA flux scale for 1934-638.
Using IQUV =  2.0947,  0.0000,  0.0000,  0.0000 at  11.0552 GHz.
Using post-Aug94 ATCA flux scale for 1934-638.
Using IQUV =  1.9910,  0.0000,  0.0000,  0.0000 at  11.5168 GHz.
Iter= 1, Amplit/Phase Solution Error:   1.369
Iter= 1, Polarisation Solution Error:   0.019
Iter= 1, Overall Solution Error:        2.259
Iter= 2, Amplit/Phase Solution Error:   0.002
Iter= 2, Polarisation Solution Error:   0.000
Iter= 2, Overall Solution Error:        0.003
Iter= 3, Amplit/Phase Solution Error:   0.001
Iter= 3, Polarisation Solution Error:   0.000
Iter= 3, Overall Solution Error:        0.001
I flux density:   2.1590
Leakage terms:
 Ant 1:Dx,Dy = ( 0.00224,-0.00724),
( 0.00193,-0.00756)
 Ant 2:Dx,Dy = ( 0.00449,-0.00172),
(-0.00168,-0.00237)
 Ant 3:Dx,Dy = ( 0.00080, 0.00298),
(-0.00563, 0.00782)
 Ant 4:Dx,Dy = (-0.01404,-0.00429),
( 0.00236,-0.00260)
 Ant 5:Dx,Dy = (-0.00002, 0.02198),
( 0.00023, 0.02032)
 Ant 6:Dx,Dy = ( 0.00257,-0.01372),
(-0.00118,-0.01361)
Solution for freq bin  1
Iter= 1, Amplit/Phase Solution Error:   1.329
Iter= 1, Polarisation Solution Error:   0.019
Iter= 1, Overall Solution Error:        2.248
Iter= 2, Amplit/Phase Solution Error:   0.002
Iter= 2, Polarisation Solution Error:   0.000
Iter= 2, Overall Solution Error:        0.003
Iter= 3, Amplit/Phase Solution Error:   0.001
Iter= 3, Polarisation Solution Error:   0.000
Iter= 3, Overall Solution Error:        0.001
I flux density:   2.3458
Leakage terms:
 Ant 1:Dx,Dy = ( 0.00225,-0.00512),
( 0.00390,-0.00475)
 Ant 2:Dx,Dy = ( 0.00387, 0.00248),
(-0.00100, 0.00244)
 Ant 3:Dx,Dy = ( 0.00253, 0.00331),
(-0.00867, 0.00024)
 Ant 4:Dx,Dy = (-0.00577,-0.00378),
( 0.01369,-0.00321)
 Ant 5:Dx,Dy = ( 0.00264, 0.01870),
(-0.00142, 0.01933)
 Ant 6:Dx,Dy = ( 0.00385,-0.01430),
( 0.00287,-0.01533)
Solution for freq bin  2
Iter= 1, Amplit/Phase Solution Error:   1.354
Iter= 1, Polarisation Solution Error:   0.019
Iter= 1, Overall Solution Error:        2.253
Iter= 2, Amplit/Phase Solution Error:   0.002
Iter= 2, Polarisation Solution Error:   0.000
Iter= 2, Overall Solution Error:        0.003
Iter= 3, Amplit/Phase Solution Error:   0.001
Iter= 3, Polarisation Solution Error:   0.000
Iter= 3, Overall Solution Error:        0.001
I flux density:   2.2203
Leakage terms:
 Ant 1:Dx,Dy = ( 0.00033,-0.00402),
( 0.00027,-0.00402)
 Ant 2:Dx,Dy = ( 0.00348, 0.00308),
(-0.00071, 0.00221)
 Ant 3:Dx,Dy = (-0.00168, 0.00052),
(-0.00888, 0.00410)
 Ant 4:Dx,Dy = (-0.00954,-0.00461),
( 0.00857,-0.00467)
 Ant 5:Dx,Dy = ( 0.00215, 0.01903),
( 0.00022, 0.01723)
 Ant 6:Dx,Dy = (-0.00028,-0.01431),
(-0.00500,-0.01454)
Solution for freq bin  3
Iter= 1, Amplit/Phase Solution Error:   1.386
Iter= 1, Polarisation Solution Error:   0.027
Iter= 1, Overall Solution Error:        2.261
Iter= 2, Amplit/Phase Solution Error:   0.002
Iter= 2, Polarisation Solution Error:   0.001
Iter= 2, Overall Solution Error:        0.003
Iter= 3, Amplit/Phase Solution Error:   0.001
Iter= 3, Polarisation Solution Error:   0.000
Iter= 3, Overall Solution Error:        0.001
I flux density:   2.0947
Leakage terms:
 Ant 1:Dx,Dy = ( 0.00046,-0.00009),
(-0.00243,-0.00514)
 Ant 2:Dx,Dy = ( 0.00780,-0.01116),
( 0.00035,-0.00982)
 Ant 3:Dx,Dy = ( 0.00301, 0.00475),
(-0.00318, 0.01589)
 Ant 4:Dx,Dy = (-0.02125,-0.00640),
(-0.00387,-0.00228)
 Ant 5:Dx,Dy = (-0.00168, 0.02625),
( 0.00204, 0.02485)
 Ant 6:Dx,Dy = ( 0.00167,-0.01951),
(-0.00291,-0.01733)
Solution for freq bin  4
Iter= 1, Amplit/Phase Solution Error:   1.391
Iter= 1, Polarisation Solution Error:   0.028
Iter= 1, Overall Solution Error:        2.272
Iter= 2, Amplit/Phase Solution Error:   0.002
Iter= 2, Polarisation Solution Error:   0.001
Iter= 2, Overall Solution Error:        0.003
Iter= 3, Amplit/Phase Solution Error:   0.001
Iter= 3, Polarisation Solution Error:   0.001
Iter= 3, Overall Solution Error:        0.001
I flux density:   1.9910
Leakage terms:
 Ant 1:Dx,Dy = ( 0.00712,-0.02368),
( 0.00835,-0.01917)
 Ant 2:Dx,Dy = ( 0.00232,-0.00068),
(-0.00672,-0.00522)
 Ant 3:Dx,Dy = (-0.00073, 0.00361),
(-0.00076, 0.01145)
 Ant 4:Dx,Dy = (-0.02044,-0.00156),
(-0.01158, 0.00064)
 Ant 5:Dx,Dy = (-0.00391, 0.02448),
(-0.00009, 0.01991)
 Ant 6:Dx,Dy = ( 0.00641,-0.00453),
( 0.00157,-0.00527)



The issue is that no matter what I do, my higher frequency end (> 11GHz) has something off going on. In the attached image you can see the effect - everything below 11GHz seems reasonable, everything above not so much. There is no such effect before I run mfcal ie. straight after atlod/uvsplit 1934 looks fine.

I do see on the ATCA user guide that the system temperature at around this frequency starts to increase (http://www.narrabri.atnf.csiro.au/obser ... emperature). It was my understanding that the bandpass calibration that mfcal performs would take care of this issue. Is the model mfcal uses incomplete at around this limit?

Any thoughts would be very helpful. Is it a case where I just have to throw everything above 11GHz away for the observation, or is there some miriad magic you could let me in on?

Thanks - Tim
Attachments
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tg1989
 
Posts: 17
Joined: Sun Dec 07, 2014 3:04 pm

Re: 1934 at 11GHz

Postby ste616 » Tue May 19, 2015 9:04 am

Hi Tim,

The feedhorn response above 11 GHz is pretty bad, and I've never been able to recover anything useful from the data that high in frequency, at least with CA01,2,4 and 6. CA03 and 5 have different feedhorns that do respond well to frequencies above 11 GHz. Unfortunately, it's hard to make a good calibration with only two antenna.
cheers
Jamie Stevens
ATCA Senior System Scientist
ste616
Site Admin
 
Posts: 217
Joined: Thu Feb 04, 2010 3:27 pm
Location: Paul Wild Observatory Narrabri NSW

Re: 1934 at 11GHz

Postby tg1989 » Tue May 19, 2015 10:42 am

Thanks Jamie. This makes sense. As I was initially inspecting the data I did notice that baseline 3-5 was the only baseline without this behavior. I'll just go ahead and flag all channels above 11GHz and move forward from there.
tg1989
 
Posts: 17
Joined: Sun Dec 07, 2014 3:04 pm


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