[mmaimcal] Meeting today

[Steven T. Myers]

A couple of comments on points where I disagree with Darrel and/or
Stephane.

The arguments about 15m baselines given a 1.5xD packing efficiency are
incorrect.  The array should function well down to the shadowing limit
(12m for ALMA, 6-8m for ACA, 9m for ALMAxACA), as do the existing arrays.

The first nulls occur at around twice the half-power radius, so the
half-power FOV of a 6m will encompass the first-null FOV of the 12m 
approximately.

It is true that the big gain in image fidelity for extended sources will
come from the baselines within the ACA, but cross-calibration between the
two on linked baselines should not be dismissed as unnecessary.  Combining
existing array data has proved to be nontrivial due to calibration issues
(though my experience is mostly with the very different sort of images
produced in CMB experiments).

Just because the ALMA and ACA *could* be used together does not mean that
they must always.  If there is a compelling reason to use different
integration times then you could just run them separately after common
calibration is over.  I think we will want the flexibility to run them
together at some times.  

I doubt that calibration sensitivity will strongly drive the number and
size of ACA antennas, given that BIMA has been running 6m antennas
successfully from a poorer site - the ACA parameters should be driven by
imaging issues as Darrel suggested.  My guess is, like ALMA itself, there
is a broad range of acceptable tradeoff of N vs D, and something like
16x6m vs 11x8m will be a wash as far as performance goes except for
imaging the largest spatial scales.  My personal opinion is that to be
complementary to ALMA we will want 6m antennas, and that these give us
more options for increasing the surface and pointing accuracies toward
the THz bands.

It is clear that we critically need the capability to do appropriate
simulations or else we will argue in circles.  How do we stand on this?
I still might be able to adapt the simulation software we use for CBI
(which includes mosaicing) but that will likely be after my travels end
in September.

   -steve

-------------------------------------------------------------------------

On Tue, 18 Jul 2000, Al Wootten wrote:

> We will meet today.  A major topic will be configurations, particularly
> for the ACA.  There are links to Stephane's text at the agenda:
> http://www.cv.nrao.edu/~awootten/mmaimcal/18Jul00.html
> 
> Please read them.
> 
> Clear skies,
> Al
>