The Dark Energy Spectroscopic Instrument (DESI): Tiling and Fiber Assignment
Abstract
DESI will measure the redshifts of 25 million galaxies drawn from a list of targets identified photometrically. The spectra will be obtained using 5000 automated positioners populating the instrument's 7.5 square degree focal plane. With about 10,000 pointings, each spot in the 14,000 square degree footprint will be covered more than five times, on average. The galaxies will be of three primary kinds, luminous red galaxies (LRGs), emission line galaxies (ELGs), and quasars (QSO).The pattern of telescope pointings generates a tiling of the sky, which we consider to be made of five separate passes, each providing nearly full coverage of the 14,000 square degrees. The first pass forms a particularly symmetric pattern. The subsequent passes are made by rotations of the first pass.For each pointing of the telescope, each fiber positioner must be directed to a galaxy within its reach. The choice of galaxy is dictated by priorities established to maximize the value of the full suite of observations. In addition to the galaxy targets, some fibers must be reserved for calibration with standard stars and others for measuring sky alone. We demonstrate the effectiveness of the fiber assignment algorithm when applied to mock catalogs observed with planned tiling patterns.
- Publication:
-
American Astronomical Society Meeting Abstracts #225
- Pub Date:
- January 2015
- Bibcode:
- 2015AAS...22533610C