[alma-config]Meeting Tuesday 16 October 2001 1415 UT

[Al Wootten]

Folks,

We agreed to have another meeting next Tuesday.  I append some notes from
the last meeting, though there has been considerable e-progress since then.
Please send agenda items to me for distribution on Monday.
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 CALL DATE:         OCT-16-2001  (Tuesday)
 CALL TIME:         10:15 AM EASTERN TIME = 1415 Universal Time
 DURATION:              1 hr
 USA Toll Free Number: 888-831-4304
 Alternative Number: +1-712-257-0430
  PASSCODE: ALMA
  LEADER:            Dr Al Wootten
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ALMA Configuration Group

Date: OCT-2-2000 (Tuesday) 2 October 2000.

Time: 10:15 EDT (8:15 MDT, 1415UT)

Conference leader: Al Wootten

Past minutes, etc on ALMA Configuration Group Page

Minutes

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Attendees: Wootten, Conway, Guilloteau, Woody, Webster, Butler, Kogan,
Sakamoto, Wright, Viallefond, Boone and Radford

Summary
>From the 21 November 2000 telecon minutes: "The plans for the layout of
the pads must be finalized by the beginning of construction. We hope 
that the first construction funds will arrive on 2001 Oct 1 when the
FY2002 begins here."

At its meeting at San Pedro and Santiago the ASAC heard presentations
on, and visited the site.  Hofstadt urged the scientists to reach a
final 
configuration plan by January 2002.  The construction funds have not
arrived yet but the construction phase of ALMA does appear to be
imminent, 
beginning possibly as soon as yesterday.  Hence, the configuration group
should act on the decisions made at its PDR and move on toward a final 
design decision.  A plan for doing this was presented, wherein
outstanding issues could be addressed by the end of the year. Biweekly 
teleconferences will be held, at which progress on designing the
intermediate configurations, and the bridge configuation between the
large 
configuration and the inner configuration, will be discussed.  

Updates

Philosophy was discussed, spurred by Woody's recent memos beam
optimization and Conway's discussion of how this provides a suitable 
philosophical basis for establishing the grand design of the array.  Pad
sharing was discussed; to some extent this compromises sidelobes.  It
was 
generally agreed that pad sharing is subjugate to scientific
considerations but the goal remains to design for 250 pads or less.

Optimization in the uv plane and in the beam was discussed.  Boone noted
that uv coverage was an important parameter for imaging considerations 
whereas beam sidelobes could be secondary.  An example of a
configuration with excellent beam properties and poor imaging
properties, or 
excellent imaging and poor beam properties, will be produced for
illustration.

Leonia noted that this is the fundamental problem of radio imaging--how
to reconstruct the image.  No configuration works which does not provide 
appropriate uv coverage, but the appropriate uv coverage depends to some
degree on the nature of the source to be imaged.  We must design a 
configuration, simulate observations with that on appropriate sources,
and select the configuration on the basis of our best results.  This was
the 
process at the PDR.

The degree of short spacing coverage in the large configurations was
discussed.  Guilloteau noted that at least enough were required to
effect 
calibration.  There was general agreement that the short spacings were
essential to imaging but no consensus on a prescription for the proper
degree of short spacing coverage.

Conway has been making progress on intermediage configurations and will
have considerably more time to work on this after 1 November.

Webster mentioned that he is working on designs for the hybrid
configurations going out to the largest configuration.  He noted that
the Project 
Book has not been updated since the PDR and still refers to 10 km as the
diameter of the larger configuration.  The Project Book chapter will be 
updated to reflect the results of the PDR and the expansion of the
project to three partners.  As a consequence, he has designs to 10km
which 
remain within the pad budget, even perhaps using on 235 pads.

Future Plans

The large configuration is bounded by the constraints of the site,
rather than by a number.  Leonia demonstrated at the PDR how an array of 
diameter roughly 14km could be accommodated on the site.  Some baselines
between the antenna stations he identified and some stations to the 
extreme SE in Conway's zoom spiral design in fact reach 17 km.  The
larger arrays should fully employ the real estate available on the site, 
consistent with the constrains that fiber optic runs will be less than
25 km.

We will arrive at at least one strawman configuration design consistent
with the results of the PDR by early December.  The Chajnantor campaign
of 
December 2001 will include an ESO engineer, to provide feedback for the
final configuration selection.  Holidays extend beyond New Year's Day 
in many countries.  URSI and AAS meetings in NA occur 6-10 January.  SG
is committed 14-18 Jan.  A strawman date for this would  then be 
after 20 January.  Possible venues include the AOC, with a visit to the
Test Interferometer site and whatever part of the Vertex antenna has
arrived, 
Tucson, or ?

The next teleconference was tentatively set for 1415UT on 16 October.