[mmaimcal]Memo 428

[Mark Holdaway]

Configurants,

I think Mel is correct to ignore the partially shadowed baselines.
The computational problem of mosaicing with such voltage patterns
is basically insurmountable for all but the most pressing scientific
problems (ie, cannot be used for every day observations) in the
near term computing environment.  Such software is possible in
principle, but we cannot count on this working for routine observations
for the first 10 years of ALMA operations.

Concerning 2 vs 3 configurations, I think there is a place for 
config 3 in the +30 to +60 degree declination range where significant
improvement in the beam shape occurs for config 3.  The main question
is now a cost-benefit analysis: does the benefit of config 3 in this
dec range justify the cost of the additional pads and the lost observing
time in the move?  We have a methodolgy for answering that question.

The problem of the number of compact configurations is significantly
simpler than it used to be: we no longer need to worry so hard about
getting lots of short projected spacings at all declinations with the
addition of the ACA (which, by the way, is costing a bit more than those
25 extra pads would have cost).

	-Mark