[alma-config] [Fwd: Re: Memo 538 draft]

[Frederic Boone]

--- Mark Holdaway <mholdawa at nrao.edu> wrote : 
> I will remind our group that in radio astronomical
> imaging
> there is nothing magical about Nyquist sampled
> visibilities.
> We cannot make a perfect image even if we have
> Nyquist
> sampling, and when we do not have Nyquist sampling,
> imaging quality degrades gracefully as the object
> becomes
> more complex or the (u,v) coverage falls off.
> 
> It has been appreciated that eventually mosaicing
> observations
> will fail as we go to higher and higher resolution
> and the
> Fourier sampling gets further away from Nyquist.
> 
>     -Mark
> 
> 

I fully agree with you Mark and I am concerned about
the uv coverage. Going from 64 to 50 antennas we loose
40% of the samples and this issue becomes more
critical.

In the design proposed in the memo draft it seems that
in a significant part of the uv-region covered by the
configurations greater than 2 km the sampling is far
from Nyquist (a least 4 times worse), whereas in
principle it could be close to Nyquist for
configurations up to 3.5 km. In other words it seems
that the sampling could be improved by optimizing the
configurations for distributions that fall off less
rapidly. 

Is mosaicing of extended sources with the
configurations of 3.5 km part of the scientific
requirements? if yes, does the design presented in the
draft meet the requirement?

Cheers,
Frederic.



 



	

	
		



	

	
		
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