[Difx-users] Question on changing data rates during observation {External} {External}

[Walter Brisken]

It depends...

The vex file which yields the .input files still need to properly describe 
the data that were taken.  If, for example, the data rate dropped because 
each channel reduced its bandwidth by 50%, that would not fly well.

However, if the data rate drop were due to some VDIF threads not being 
generated / recorded, that is a case where DiFX can cope.  Newer versions 
(trunk and the soon-to-be-released 2.8 series) handle this case better 
than previous versions.

 	-Walter

-------------------------
Walter Brisken
NRAO
Deputy Assistant Director for VLBA Development
(505)-234-5912 (cell)
(575)-835-7133 (office)

On Thu, 9 Mar 2023, Geoff Crew via Difx-users wrote:

> If what was done is consistent with the experiment vex.obs file, then ""the 
> is answer is no", but:
>
> It depends a bit on what you mean about recording rates.  If you are 
> switching the recording setup, then you will need a mode (for all stations) 
> that explains what mode on the relevant scans was used.
>
> If you are dropping half of the data on the floor, results will depend on 
> what you actually dropped.
>
> DiFX can't read anyone's mind or reverse engineer crazy things that happen in 
> the field.  That is always what the operators have to deal with....
>
> On 3/9/23 11:13, Michael Dutka via Difx-users wrote:
>>  Hi All,
>>  A coworker of mine had a question on changing data rates during an
>>  observation.  She wants to know if you would have to do 2 different
>>  calls to difx for each recording rate.  I think the answer is no
>>  because the VDIF data should have all the info difx needs to know what
>>  to do, but I want to confirm that.
>> 
>>
>>  "Is DIFX smart enough to adjust the recording rate of a VDIF station
>>  during correlation? Katherine recorded at 256 Mbps for the first 3.5
>>  hours of R41091, then swapped down to 128 Mbps for the rest."
>>
>>  -Mike
>> 
> -- 
> Geoff Crew
> gbc at haystack.mit.edu
>
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