[alma-config]Comments on Memos 389 and 390 (fwd)

[David Woody]

All

I don't think we are starting from scratch.  I think we have
made great progress in understanding the issues and metrics
for array configuration design and most of necessary tools
have been built.  Once we decide on what we want in terms
of metrics, operations and have the proper masks, the actual
configurations can be generated and optimized quickly.
Their image quality can then be compared against the
existing imaging results that have already been generated to 
verify that they work as expected.

As I see it, we do need to make some decisions above and beyond
the basic desire for Gaussian UV coverage that was agreed
to a year ago.  (I was unable to attend last years meeting and
am probably repeating a lot of what was said or presented there.)
1.  How much reuse of pads do we want, range?
     25-50%
2.  Do we want to strive for positive PSF (without single
dish data) out to ? times the synthesized beam?
     add (how many?) short spacings or not
3.  What is the criteria for the largest configuration? 
     Gaussian UV or circle array
4.  What criteria do you want for the most compact configuration? 
     Gaussian UV or filled aperture
5.  Where does the ACA fit in?
     off to the side or incorporated into the middle of the array
There are probably other issues that need to be discussed and
decided.  We should have a list of the these.

This is clearly more than we can accomplish during infrequent meetings
over the next two months.  We either need weekly meetings with
a lot of people doing lots of work or a more sensible pace for
arriving at the final master plan.  To this end what is it that is
actually needed in December and what is going to be done with it?
We surely aren't going to be pouring concrete, the multiple competing
antenna prototypes with different pad requirements are more than a
year from a decision point.  Basic array layout in terms of where 
the array center will be and where the buildings will be put could
be used for initial road construction.  This can be handled by allocating
a building space in some sensible place and a major access road to
the building to the mask.  Conway's zoom spiral configurations
could be used for a first cut to determine where the buildings and access
road might fit.

My feeling is that the most compact configurations and the location of
the ACA are the most contentious and will take awhile to resolve.
To this end we should reserve something on the order of 200m diameter
circle with no interfering buildings or access roads. 

Cheers
David

****************************************
| David Woody
| Owens Valley Radio Observatory
| P.O. Box 968, 100 Leighton Lane                         
| Big Pine, CA 93513, USA                                  
| Phone 760-938-2075ext111, FAX 760-938-2075
|dwoody at caltech.edu 
****************************************
----- Original Message ----- 
From: "Bryan Butler" <bbutler at nrao.edu>
To: "David Woody" <dwoody at benton.ovro.caltech.edu>
Cc: "John Conway" <jconway at oso.chalmers.se>; <alma-config at nrao.edu>
Sent: Monday, October 01, 2001 2:23 PM
Subject: Re: [alma-config]Comments on Memos 389 and 390 (fwd)


> 
> all,
> 
> forgive me if i'm way off here, but isn't it a bit late in the game
> to start from scratch?  we don't really have 6 more months or another
> year to play around with different optimization techniques - we need a
> quasi-final design by the first part of december (al, correct me if i'm
> wrong here).
> 
> -bryan
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