[alma-config] telecon this Wednesday

[Mark Holdaway]

On Wed, 7 Jun 2000, Min Yun wrote:

> Morita-san,
> 
> Looking at your latest report, I am struck by the fact that the
> sidelobe behavior of the spiral configuration is not as good as it 
> can be (John must be working on optimizing this right now).  
> If one of your conclusions is indeed a possible correlation 
> between the sidelobe levels and imaging quality, then 
> there are even more reason to include
> the donut strawperson configurations to your tests.  

Remember that the donut arrays are the results of optimizing the
sidelobes for a SNAPSHOT, and that John convincingly demonstrated
that the nearin sidelobes don't average down with long integrations.
The distinction between nearin and farout sidelobes is somewhat unclear,
but image dynamic range (measured by looking far off the source) should
be related more to far out sidelobes.  In Morita's test image, composed
of small Gaussians (which does not require mosaicing), the on-source
errors may be more dominated by the near in sidelobes.

Perhaps the direction we should be going in is: over what range of
hour angles is it relevant to try to optimize the sidelobes over?
The compact configuration, which will do many snapshot mosaics, should
have the lowest sidelobe levels possible for snapshots.  The larger
configurations might have hour angle ranges for sidelobe optimization
which is given by some criteria similar to what I did in MMA Memo
201.

> As you stated
> at the beginning, comparing the two extreme cases should give us
> the ranges of outcomes we may expect from these imaging simulations,
> but it is unavoidable that you should also compare the spiral and
> donut arrays directly.  Even your possible conclusion that the
> two produce nearly identical results should be a useful and tangible
> work in making further decisions down the line.
> 

True.
I was somewhat disturbed though, that the simulation plans are ahead of
discussion of the pointing error results in the agenda.  It is
exactly backwards: the whole point of the pointing error simulations
was to say that the original simulation plans were flawed.
Would you consider reordering the agenda?

	-Mark