[evlatests] EVLA Holography -- almost working!

[Bryan Butler]

i am going to look into this tonight or tomorrow.  i'm pretty sure i can track 
down the cause for 1) and 2).

	-bryan


On 3/5/07 17:29, Rick Perley wrote:
> A quick test was done this afternoon to test EVLA Holography.   In this 
> test, three VLA antennas and two EVLA antennas were declared as 
> references.   The others executed a standard 11 x 11 raster, with twice 
> critical spacing (two points per beam). 
> 
> Three problems were found -- two of which are fundamental, the other a 
> fluke (note:  not Fluke!) 
> 
>     A) Fundamental problems.
> 
>        1)  The EVLA and VLA are not perfectly synchronized.  Each array 
> is executing the proper pattern, but the EVLA is running about 4 seconds 
> behind the VLA in its movements! 
> 
>     2)  The EVLA's reference antennas are being told to go to the first 
> offset holography position -- where they spend 10 seconds -- then they 
> are told to do what was intended of them in the first place -- and rush 
> off to remained fixed on the source. 
> 
>        B) Fluke (NB NOT the Flukes of recent fame) Problem. 
> 
>     All EVLA to VLA baselines were low by about a factor of four for the 
> first 20 minutes of the 30 minute test.  But the EVLA to EVLA baselines, 
> and VLA to VLA baselines were normal, or near normal.  Ken has a 
> rational explanation for this, involving the fact that the EVLA antennas 
> were not being utilized in the run preceding this test, and were not 
> properly returned until well into this test.  The loss of amplitude was 
> because the EVLA test was at 12.5 MHz BW, while the antennas were 
> apparently left in a 50 MHz BW.   He can explain the curious set of 
> circumstances needed to create the effects we see.  He is confident this 
> is a 'one-of' type of problem.  (Right, Ken?) 
> 
> 
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