[alma-config]Update

[Al Wootten]

Folks,

While there has not been a lot of traffic on alma-config recently,
 a lot has been going on.  John Conway delivered a configuration about
in September to the Joint ALMA Office (JAO) and to Holdaway, who began
using this configuration set to build the Y+ set.  On 1 October, the
Project Office approved John's set (which he is still refining);
Mark will present his first iteration very soon.  I put a link 
to a copy of Conway's presentation to the ASAC, and to the JAO report at
http://www.cv.nrao.edu/~awootten/mmaimcal/29oct02.html

The Site Infrastructure Review was last week in Tucson.  There the needs
for the site were described to engineers and architects, including Conway's
pad locations.  We also had a transporter review.  There is a huge
moving .gif file of it at:
http://www.cv.nrao.edu/~awootten/mmaimcal/transporter.html
but loading it slows my computer to a crawl--beware!  watch in awe
as the tranporter plucks the antenna from the pad, hoists it over the
operator cab and places it on its back for transport.

Below I have extracted the relevant sections
from recent Science IPT reports to management which cover configuration
and related subjects.  


               Science IPT Monthly Summary to the JAO
               ======================================
               E. van Dishoeck and A. Wootten
                   September 2002


Configuration:
-------------

During September, configuration leader Conway delivered a plan for
configurations covering less than 4 km in extent to the JAO.  For the
compact array configurations, special attention was paid to minimizing
shadowing losses as well as improved image quality of far Southern
(e.g., Magellanic Clouds) and far Northern sources.  For the intermediate
configurations, the zoom spiral array design has been adopted, which
is continuously reconfigurable.  This plan has been reviewed
critically by the JAO, in particular Guilloteau, and has been accepted
as final.

Upon receipt of Conway's plan, Holdaway began designing the interface
from the largest Conway spiral array to the more extended Y+
configurations.  The choice of the Y+ configuration rather than the
large 14 km ring array was made earlier this summer, with arguments
including operational simplicity, the natural intermediate resolution
configurations, the sometimes superior imaging quality, and the
potential to expand to longer baselines in the future.  The maximum
baseline in the Y+ array is 18 km, leading to images of 13-16 mas at
300 GHz. [AW-Last week it had grown to 20 km] In response to 
questions at the ASAC meeting, further
optimization of the Y+ array to image sources on the smallest angular
scales is currently in progress.  These simulations use a new
topographical mask reflecting the ALMA concession boundaries, as well
as the prescription used by Conway for the inner configurations.


                 Science IPT Report to the JAO
                 =============================
               E. van Dishoeck and A. Wootten
                  October 2002

Configuration:
-------------

During this period, the JAO approved the plan delivered by Conway for
configurations covering less than 4km in extent to the JAO.  Holdaway
continued designing the interface from the largest Conway array to the
more extended Y+ configurations.  A new detailed map of the site,
accurate to a few meters, was delivered and Conway began taking into
account new details of the terrain to mate the array configuration to
it.  The required precision on the station coordinates for uv
coverage/beam constraint purposes has been quantified, which is needed
to convert the JAO report into an engineering specifications
document. Conway has also started to address queries in the comments
on his report to the JAO, including reconfiguration schemes for 4
antenna moves at a time rather than 3, and accomodation of
observations at extreme declination (e.g North of +35 degrees). New
visualization tools for the array design have been developed.

Site Characterization:
----------------------

A new map of the site, much more accurate than those previously
available, was delivered.


Clear skies,
Al