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

[Fred Schwab]

I'd be interested in having a look at the Memo 538 draft, but
I don't have an ALMA EDM login or password (the first message
on this thread gave a pointer to the URL of the EDM location).
Could somebody e-mail me a copy?
                                         - Fred Schwab

On Tue, 4 Oct 2005, Frederic Boone wrote:

> --- 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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