[Difx-users] integration time

[Adam Deller]

Hi Sam,

Integration time will affect the maximum fringe rate you are sensitive to.
Shorter integrations = higher fringe rate before you lose signal due to
decorrelation.  But normally this is not a limitation.  I would be fairly
surprised if a 1 second integration time was a problem (unless there is an
issue with the observing setup).

Spectral resolution will affect the maximum residual delay you are
sensitive too.  Finer spectral resolution = larger delay before you lose
signal due to decorrelation.

These are not DiFX-specific things, but general to radio interferometers /
correlators.  To know what values are reasonable, you need to know your
instrument and what the expected residual fringe rate and delay are.

Cheers,
Adam

On 12 May 2017 at 23:59, Hagatiana Andrianomena <handrianomena at ska.ac.za>
wrote:

> Hi DiFX users,
>
> I got a question regarding the integration time in the setup:
> SETUP default
> {
>   tInt = 1.000000
>   fftSpecRes = 0.12500000
>   specRes = 0.12500000
>   doPolar = True
>   maxNSBetweenACAvg = 2000000
> }
>
> I got this default setup by running oms2v2d using the .oms file from the
> experiment. When running the difx I got no fringe but from changing the
> tInt to
> 0.08 and both fftSpecRes and specRes the result seems to suggest I got
> fringe (see plot attached).
>
> I am not quite sure whether it is a naive question but I wonder if there
> is a simple rule of thumb to get the right values of those parameters in
> order to get fringe. I do not have much experience with DiFX I must say
> though.
>
> Regards,
> Sam
>
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>


-- 
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Dr. Adam Deller
ARC Future Fellow, Senior Lecturer
Centre for Astrophysics & Supercomputing
Swinburne University of Technology
John St, Hawthorn VIC 3122 Australia
phone: +61 3 9214 5307
fax: +61 3 9214 8797

office days (usually): Mon-Thu
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