Subarrays

[Barry Clark <bclark@aoc.nrao.edu>]

Come on people, I know it's a dull subject, but it's our job.  Is there a
scientific requirement for the software to enable the observer to 
shuffle antennas flexibly from one subarray to another?


> We seem to be agreed that we want some sort of scripting language for
> the direct interface to the real-time system.  In designing this language,
> a pivotal question is whether we want to give the observer the power to 
> shuffle antennas from one subarray to another via script.  To do so complicates
> things considerably, so I would like to close that door unless it is really
> needed.
> 
> 1.) It might be desired for transient phenomena.
> One might want to record an instantaneous SED.  For phenomena with 
> timescales greater than tens of seconds, it is more effcient to just 
> cycle the array through the frequencies, rather than splitting into 
> subarrays.  The faster timescale phenomena that come to mind are 
> a). pulsars, b).  solar flares, and c). maybe flares on other stars
> (the fine time-structure stuff may have such a steep spectrum that 
> ALMA won't see it).  (Am I missing something?)
> 
> Note also that subarraying capability has to be provided for other reasons.
> So, giving the observer the capability to rearrange his subarrays by 
> script is called for only if this subarraying is pretty dynamic.  For
> instance, the observer might want to occasionally recombine his subarrays
> for calibration purposes (could use a weaker calibrator that way).
> 
> 2.) It might be useful for instrumental reasons.
> For instance, if the observer is switching between two frequencies, and
> not all antennas are equipped with the receiver for one of these, 
> he would like all antennas to join in when he is at the frequency that
> they all have, but would have the incomplete antennas go off and do
> something else possibly useful when he is observing at the other.
> 
> Am I missing other scenarios?
> 
> Do these two justify the complexity of including this in the scripting
> language?
> 
>