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ALMA MEMO #479

Requirements for Subreflector and Feed Positioning for ALMA Antennas


Bryan J. Butler
National Radio Astronomy Observatory

2003-12-08



This memo presents some calculations related to requirements on subreflector and feed positioning for the ALMA antennas. In order to keep gain loss at less than 1%, the axial (vertical) positioning error in the subreflector should be less than about 0.09 λ, and in the feed should be less than about 0.9 λ. The lateral positioning error for the subreflector should be less than about 0.45 λ, and for the feed should be less than about 10 λ. The rotational (tilt) error of the subreflector should be less than about 5.5 λmm arcminutes if the rotation is about the vertex of the subreflector.


View a pdf version of ALMA Memo #479.






Last modified: 2004-01-07

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