[Evla-eng] Re: [evlatests] EVLA Cable Wraps

[Jim Ulvestad]

I'd have to re-read Bob's note, but I'll simply say for the record
that scheduling observations on the VLA was a nightmare in the
early 80s, when antennas seemed to be on different wraps, and
whatever fix was applied was greeted with great sighs of relief
from people like me.  I think that's what Barry is referring to.

Jim

Barry Clark wrote:

>Bob Broilo wrote:
>
>  
>
>>Since the EVLA software knows which arm the antenna is on, it could
>>apply this simple offset and improve the situation for servo,
>>astronomers, and operations.
>>
>>Please consider this simple software change,
>>-Bob.
>>    
>>
>
>
>If I may recall a bit of ancient history, the VLA was originally organized
>this way; it seemed as logical to me then as it does to you now.  Turns
>out it drove the observers crazy.  Problem is that different arms may move
>in opposite directions in azimuth, resulting in an appearance of more net 
>move time, since you don't get full data rate until the slowest arm gets on
>source.  Perhaps as important, it made it intolerably confusing for the 
>astronomer to plan his observation in detail.  The current system was 
>implemented in the early eighties, and regarded as a vast improvement.  It 
>could be implemented with a different mix of hardware and software if we
>need to, but the central feature - that the highest level software regards 
>all antennas as having the same azimuth limits, in true azimuth, needs to be
>preserved.
>
>If the hardware problems are too difficult, we might consider reducing the
>azimuth range.  There is nothing magic about 540 degrees, it is just nice.
>A moderate overlap is imperative to keep from having to unwrap too often, 
>but we could shave a bit.
>
>I did not understand your remark about needing to move the 'flipper' when the
>antenna changes arms.  This sounds like you are applying the 'flipper' 
>after the subtraction of the arm offset.  Doesn't it make more sense to 
>apply it before?
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