[daip] ACCOR

[Z.-Q. Shen]

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
>
>