Memo Review

Memo: 403 - Fast Switching Phase Correction Revisited for 64 12 m Antennas
      Holdaway, 2001Dec17

Reviewer: Dave Woody

Date Received: 2002Aug08


Review:

This is difficult to review since a lot of the information
is contained in AIPS++ code and glish scripts.
It would help to add a more detailed or
explicit description of the optimization algorithm.

Not all of the references are in reference list, i.e. Butler
and Wooten 1999 and Delgado 2001.  I assume these are
ALMA memos.

It would be useful if the critical data used
from the references were presented in this memo so that
the reader can readily see what the assumptions are,
i.e. atmospheric opacity and receiver noise temperatures
vs. frequency.  This information could be included in
table 1.  It is painful for the reader to have to go back to
the references and dig out the numbers and then you are not
sure they are same ones used in this analysis.

The results depend critically upon the assumed 500m height
for turbulence from Memo 345.  The analysis is memo 345 has
a few key assumptions, such as the wind speed being uniform
through the atmosphere, which can effect the conclusion.
It would be useful to have the fast switching results
calculated for a higher turbulence height, such as 2km.

In general the results are probably correct for the
assumptions used, although doing a phase calibration
with 18msec of data seems scary.  This will be a very
useful reference memo for ALMA.  If the assumptions
and hence the conclusions are wrong the consequences
for the ALMA project are small.  You will just have to
refine the fast phase cal strategy, lose a little
efficiency, and rely more on radiometric phase correction. 
But if this memo is used to justify not doing radiometric
correction, then possible errors in the assumptions
are very serious.