[daip] ACCOR

Sat Dec 13 22:44:32 EST 2003

Hi Leonia,

I am attaching a gzipped file (POSSM.plot.gz). It contains
15 plots from POSSM for different sources/scans as follows.

plot_09.pdf  (1st calibrator scan 3C273)
plot_10.pdf  (2nd calibrator scan 3C279)
plot_11.pdf  (3rd calibrator scan 3C345)
plot_12.pdf  (4th calibrator scan OV-236)
plot_13.pdf  (5th calibrator scan 3C454.3)

 and seven (7) scans on SgrA* at different time ranges
plot_15.pdf; plot_17.pdf; plot_19.pdf; plot_20.pdf; 
plot_21.pdf; plot_23.pdf & plot_24.pdf.

 plus three (3) scans on VX_SGR of 2 minutes
plot_22.pdf;  plot_25.pdf & plot_26.pdf

Actually, the correlator has also generated the AC plots
which are kept at the VLBA HP with some other info for 
the experiment BS131A. 

This kind of difference is not significant (only a few per cent), 
but very distinct. This is why it puzzles me. I saw almost the
same plots in my previous 3mm VLBA experiment too.

I'd like to hear more from you.

Thanks.

Eric

----- Original Message -----
From: Leonia Kogan <lkogan at aoc.nrao.edu>
Date: Friday, December 12, 2003 11:29 pm
Subject: Re: [daip] ACCOR

> Hi Eric,
> 
> >As you predicted, there are corresponding differences. 
> 
> This fact explains the SN table output of ACCOR.
> Now there is the question: why this difference has a place
> 
> >I can send you some plots, if you want. 
> 
> Yes, I want
> 
> >ACCOR solutions are inversely proportional to the amplitudes of 
> the 
> >auto-correlation.
> 
> Yes, This is what ACCOR should produce
> 
> >But I am not so clear about how to get the number in SN table. It 
> is said 
> >that the
> >mean values of the AC should be close to the unit. So, I guess 
> this is a 
> >relative
> >number. If so, which one is the reference?
> 
> This number is relative to the ideal sampler at the digital 
> converter of the 
> given antenna and If at the given time. There is no reference. I 
> repeat 
> this number is absolute number which shows the distinction of the 
> given 
> digital converter from the ideal one. If the number is equal 1, 
> then 
> the digital converter is ideal.
> 
> >The next question is what is the cause for such a difference we 
> see in the 
> >ACCOR
> >solutions. Or, why does the AC amplitude change at MK?
> 
> This is a question we have to answer here having analized your data
> 
> >What is the difference between setting
> >digicor=1 in FITLD and running ACCOR?
> 
> You have to put DIGICOR=1 for future running of ACCOR.
> Having DIGICOR=1, FITLD provides the digital correction including 
> multiplication by the coefficient which makes the mean value of the 
> spectra 
> equaled 1 for VLBA correlator and for ideal digital converters.
> 
> Leonia
> 
> 
> 
> ----- Begin Included Message -----
> 
> From zshen at center.shao.ac.cn Thu Dec 11 23:43 MST 2003
> Date: Fri, 12 Dec 2003 14:43:12 +0800
> From: "Z.-Q. Shen" <zshen at center.shao.ac.cn>
> Subject: Re: [daip] ACCOR
> In-reply-to: <200312111642.JAA03295 at bonito.aoc.nrao.edu>
> To: Leonia Kogan <lkogan at zia.aoc.nrao.edu>
> Cc: daip at bonito.aoc.nrao.edu
> MIME-version: 1.0
> X-Mailer: QUALCOMM Windows Eudora Version 6.0.0.22
> Content-transfer-encoding: 7BIT
> References: <200312111642.JAA03295 at bonito.aoc.nrao.edu>
> X-MailScanner-Information: Please contact postmaster at aoc.nrao.edu 
> for more information
> X-MailScanner: Found to be clean
> X-MailScanner-SpamCheck: not spam, SpamAssassin (score=-6.3, 
> required 7,
> 	BAYES_01 -5.40, EMAIL_ATTRIBUTION -0.50, IN_REP_TO -0.37,
> 	REFERENCES -0.00, REPLY_WITH_QUOTES 0.00)
> X-Lines: 60
> Status: RO
> 
> Hi Leonia,
> 
> I tried the POSSM for both calibrators scans and SgrA scans. As you 
> predicted,there are corresponding differences. I can send you some 
> plots, if you 
> want. The
> ACCOR solutions are inversely proportional to the amplitudes of the 
> auto-correlation.
> But I am not so clear about how to get the number in SN table. It 
> is said 
> that the
> mean values of the AC should be close to the unit. So, I guess this 
> is a 
> relative
> number. If so, which one is the reference?
> 
> Though there are differences in the amplitude of the AC data, 
> almost all 
> the AC
> data have the same bandpass shape, suggesting the bandpass response 
> is stable.
> 
> The next question is what is the cause for such a difference we see 
> in the 
> ACCOR
> solutions. Or, why does the AC amplitude change at MK? Is this 
> related to 
> the data
> recording, or the correlation? I saw this happened in another 3mm 
> experiment too.
> 
> Furthermore, I see there is a parameter in FITLD, digcorr, to 
> control the 
> application
> of the VLBA correlator's digital correction. What is the difference 
> between 
> setting
> digicor=1 in FITLD and running ACCOR?
> 
> Cheers,
> Eric
> 
> 
> At 00:42 2003-12-12, Leonia Kogan wrote:
> >Hi Zhiqiang,
> >
> >ACCOR is rather simple program. So I do not think that there is 
> any bug
> >in the code (although everything can happen).
> >
> >ACCOR measure the mean value of the autocorrelation spectra.
> >
> >So it would be good to check the data itself.
> >
> >Please, look the autocorrelation spectra at  calibrators times and 
> the SgrA
> >time. To do this you need running POSSM
> >with APARM(8)= 1 => plot total power
> >Use TIMERANG specifiing the given times
> >
> >I guess you'll see a difference between short and long scans and 
> between>IF=1,7 and IF=2-6, 8
> >
> >Let me know the result of this test
> >
> >Thanks
> >
> >Leonia
> >
> >
> 
> 
> 
> ----- End Included Message -----
> 
> 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: POSSM.plot.gz
Type: application/x-gzip
Size: 573189 bytes
Desc: not available
URL: <http://listmgr.nrao.edu/pipermail/daip/attachments/20031214/5b57c35b/attachment.gz>