[mmaimcal] Re: subarrays

[Al Wootten]

Michael Rupen writes:
 > ...* Single-dish observations.  ALMA will probably do its own single dish work,
 >   but it's not clear whether one wants (or will be able) to use the entire
 >   array for this all at once.  So we'll want to split off bunches of single
 >   dishes, which you may or may not want to call subarrays....
Each element of the array will operate in a total power mode.  I suppose we
call one of these elements a separate subarray when it is doing something
entirely different (frequency wise) from the rest of the array.  Having
one telescope which operates this way has been part of the baseline plan
from the beginning of the project.  This is significant science which cannot
be done unless we allow it; particularly there will be an element which may
be used for single element single receiver sorts of experiments (the [N II]
line at 205 microns) on occasion.  That element would be operating 
independently of the array during its specialized experiment.  I fully expect
that some element of the array will operate in this mode or a similar one for
much of the time.  There isn't a proposal yet for a bolometric camera on
such an element but there will be; such an instrument would be very powerful
and in great demand.  Is such an antenna a subarray?

If so, three subarrays is an absolute minimum, in my opinion.

I'd imagine that the cost of subarrays isn't really a dollar quantifiable
item; part of the problem must be the complexity, which I would imagine could
grow to unmanageable proportions.

Al