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An Efficient Algorithm for Positioning Tiles in the Sloan Digital Sky Survey

M. R. Blanton·R. H. Lupton·F. Miller Maley·N. Young·I. Zehavi·J. Loveday
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Abstract

The Sloan Digital Sky Survey (SDSS) will observe around 10^6 spectra from targets distributed over an area of about 10,000 square degrees, using a multi-object fiber spectrograph which can simultaneously observe 640 objects in a circular field-of-view (referred to as a ``tile'') 1.49 degrees in radius. No two fibers can be placed closer than 55'' during the same observation; multiple targets closer than this distance are said to ``collide.'' We present here a method of allocating fibers to desired targets given a set of tile centers which includes the effects of collisions and which is nearly optimally efficient and uniform. Because of large-scale structure in the galaxy distribution (which form the bulk of the SDSS targets), a naive covering the sky with equally-spaced tiles does not yield uniform sampling. Thus, we present a heuristic for perturbing the centers of the tiles from the equally-spaced distribution which provides more uniform completeness. For the SDSS sample, we can attain a sampling rate greater than 92% for all targets, and greater than 99% for the set of targets which do not collide with each other, with an efficiency greater than 90% (defined as the fraction of available fibers assigned to targets).

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M. R. Blanton, R. H. Lupton, F. Miller Maley, N. Young, I. Zehavi, J. Loveday. 2001-05-30. An Efficient Algorithm for Positioning Tiles in the Sloan Digital Sky Survey. https://doi.org/10.1086/344761

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