[alma-config] The compact configuration

[John Conway]

Hi Leonia et al,

  I think the idea of starting with a design which 
incoporates the practical constraints (for the most compact 
one this is antenna access)  and then optimising is a good
one. This 'roads first' way of doing things is therefore 
probably the right way to go for the most compact array.


 The question of whether a maximum flling array or 
a more relaxed/tapered one with lower sidelobes is
better is largely an astronomical  question, whether to trade a
( probably small amount) of imaging fidelity for the capability  
of the highest brightness temperature sensitivity.  The
PDR review comittee thought this trade was worth
so I guess we don't have to discuss the question. 

 I was wondering where we might place ACA in your design.
You could place 7 small antennas say just to the
North of the whole thing (say coordinate 100m,180m
in your fig 1), giving minimal shadowing for 
N hemisphere sources, but then there are only 2 of the
12m ajoining the 6m antennas. Other possibilitis are 
to put the cluster of 6m antennas in the middle of the roads (you 
could squeeze just about 7 antennas into a 20m by 20m area)
say at 100,160 or 100,120 here  there will 4 of the 12m ajoining 
the 6m as recommended by the PDR, but more shadowing. 
The road will of course be blocked, but its not needed to
accesss all 12m from both sides. Minimal shadowing in the N-S direction
could be provided by placing the ACA  at the junctions
at say 125,100 or 160,100

One could incorporate ACA in by adding a black 'terrain constraint'
circle  corresponding to the size of ACA (or possibilty a N streched egg
shape or N-S ellipse to respectively reduce shadowing by 12m in the 
Northern  hemisphere   or North and South respectively).
and then do the optimistation on the 12m with roads + ACA mask.

 It would be good if you could also provide uv coverages and histograms
of baseline length coverage for your protomemo design, which is critical I
guess for evaluating mosaicing performance, and of course do the mosiacing
simulations. Perhaps you could also provide by email or on the web a file
with the antenna positions of the present design
(e.g in UVCON format) which we could load into our own software.

    Cheers
     John.



On Mon, 16 Apr 2001, Leonia Kogan wrote:

> As I remember it was recomended by the committee at Grenoble to present a 
> compact configuration at the middle of April.
> 
> I have put the version of the compact configuration at my web side:
> 
> http://www.aoc.nrao.edu/~lkogan/comp_conf.ps
> 
> I am looking forward seeing the discussion of the configuration.
> 
> Leonia
>