[mmaimcal] Implementation of ALMA correlator multi-resolution modes

[Al Wootten]

Rich Lacasse asked me:

"ALMA Memo 556, by Escoffier et al.,

http://edm.alma.cl/forums/alma/dispatch.cgi/almamemos/showFile/100591/d20080819212956/No/ALMA%20Memo%20556.pdf

describes observational modes supported by the ALMA 64-Antenna 
Correlator.  One class of modes is called "multi-resolution" modes.

It has recently been found that this class of modes is only partially 
implemented.  It is also not clear which aspects of this class of modes 
are scientifically valuable (i.e., would actually be used).  Before 
changing the interface with the Computing IPT and before changing 
correlator firmware, we thought it would be valuable to have a short 
discussion with you to get some perspective on exactly what should be 
implemented. I, for one, have too often been the designer (victim?) of 
elaborate hardware and software features that have never been used."

We're having a discussion about this at NTC on Thursday morning, which 
I'll attend.  I'd be very interested in your views and on specific 
examples of multi-resolution modes for which you would be a proponent.

At ALMA we have already attempted the mode in which we have a low 
resolution 2GHz window in  which to identify features (unwanted spectral 
features in this case) but then to further characterize them had a high 
resolution window superposed.  We discovered that the software did not 
support this mode after some amount of effort was expended on it.

A clear science case is in planetary atmospheres, where 
pressure-broadened wings skirt a narrow line core; inversion of the 
whole profile provides a good probe of atmospheric physics.

Clear skies,
Al