[alma-config]Sampling and Linear Reconstruction

[John Conway]

Hi,

 I have put on my web page at 
http://www.oso.chalmers.se/~jconway/ALMA/SIMULATIONS/
two proto-memos. The first is somewhat tangential 
to our array design problem the second is more relevant,
so if you have limited time look at the second one first.

1) The first memo is 'No10 Comments on Non-Regular sampling' - 
I  sent this out about a month ago on the exploder 
but it bounced because it was too large. I deals with 
the condition for unique reconstruction for an unevenly 
sampled (but repeating) sampling pattern. I basically 
reinvented the wheel because as Dave Woody noted a week or
two back Bracewell deals with  this in his book  (in in 
a much simpler and elegant signal domain rather than my uv 
domain way), however in this memo there is quantification of the
sensitivty to thermal noise for irregular sampling which is not in
Bracewells treatment. 

2) The second in 'No12 Linear Restoration via Inverse and 
Pseudo-Inverse Algebraic methods' deals with some subsequent
experiments with matrix algebra based reconstruction 
of 1D simulated sources and 1D uv coverages, this 
is promising since it appears to show  that - just using linear methods- 
several thousand to one  dynamic range images can reconstructed via this
method,  even with highly tapered  uv coverages which are 
sub-Nyquist sampled at the edge. It should be straightforward  to 
simulate the case of a 2D instantaneous ALMA snapshot, from a 60 
antenna array (if my computer memory proves sufficient).

Cheers
 John