Adrian Webster [1]
February 18, 1999
Keywords: Aperture synthesis, hybrid arrays, zoom telescopes
A design for the MMA is considered that is a composite, made up of a compact, an intermediate and an extended configuration, and the possibility is investigated of hybridizing these configurations in order to provide the ability to zoom. The quality of the beams resulting from various hybridization strategies applied to the inner hybrids (those between the compact and intermediate configurations) is found to depend strongly on the details of the geometrical design of the configurations and on where exactly the antennas are sited, but the best of the hybrids have excellent beam profiles with very low levels of sidelobes. There is less variation in the quality of the outer hybrids, all of which show a progressive increase in sidelobe level as antennas are moved from the intermediate to the extended configuration; the interesting result is found that the array may be built with a wide gap between these two configurations without adversely affecting the quality of the beams, enabling not only a significant reduction in infrastructure costs but also the accommodation of the array to the topography of the site at Chajnantor. The study is based on a continuum approximation and must be checked against a calculation based on a more detailed discrete model, but the results support the view that it may be possible to design the MMA as a telescope with a full zoom capability having beam profiles of acceptable quality over the entire zoom range.
[1] Royal Observatory Edinburgh
View a PDF version of MMA Memo #239.
Download a 0.6MB gzipped postscript version of MMA Memo #239 from
Last modified: 09 December, 1999
kweather@nrao.edu