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ALMA Memo #320
Strawperson Donut/Doubling-Ring Configurations

M.S. Yun & L. Kogan
August 24, 2000

The main motivation for the ALMA configuration design is delivering the best imaging performance possible given its number of antennas and the site limitations. The sensitivity and resolution requirements are driven by the scientific needs. Fourier plane coverage and the inclusion of short spacing information will dictate whether the target source brightness distribution can be faithfully recovered.

There are also practical concerns such as the array construction and op- eration costs. The cost of building antenna pads, cabling, and service roads is a substantial fraction of the total project budget (reference costing docu- ments), and maximum sharing of the pads is one of the practical goals for the array design. Operational issues such as the ease and speed of reconfiguration also have an impact on the long term cost of the array (see Holdaway 1998a, Yun & Kogan 1999, Guilloteau 1999).

In this memo, we present a set of strawperson configurations for ALMA based on a "donut" or "double-ring" layout that are capable of addressing a number of these scientific and operational concerns. There are significant motivational and operational differences between our strawperson concept and the spiral zoom array concept proposed by Conway (2000a,b) as de- scribed below.

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Last modified: August 25, 2000

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