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Proceedings Paper

ProtoDESI: risk reduction experiment for the Dark Energy Spectroscopic Instrument
Author(s): Parker Fagrelius; Charles Baltay; Christopher Bebek; Robert Besuner; Francisco J. Castander; Arjun Dey; Elizabeth Buckley-Geer; Ann Elliott; William Emmet; Brenna Flaugher; Irena Gershkovich; Klaus Honscheid; Dick Joyce; Stephen Kent; Robert Marshall; Ronald Probst; David Rabinowitz; Kevin Reil; David Schlegel; Michael Schubnell; Santiago Serrano; Joseph Silber; David Sprayberry; Greg Tarle
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Paper Abstract

The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 40 million galaxies over 14,000 sq. deg. will be measured during the life of the experiment. A new prime focus corrector for the KPNO Mayall telescope will deliver light to 5000 fiber optic positioners. The fibers in turn feed ten broad-band spectrographs. We describe the ProtoDESI experiment, planned for installation and commissioning at the Mayall telescope in the fall of 2016, which will test the fiber positioning system for DESI. The ProtoDESI focal plate, consisting of 10 fiber positioners, illuminated fiducials, and a guide, focus and alignment (GFA) sensor module, will be installed behind the existing Mosaic prime focus corrector. A Fiber View Camera (FVC) will be mounted to the lower surface of the primary mirror cell and a subset of the Instrument Control System (ICS) will control the ProtoDESI subsystems, communicate with the Telescope Control System (TCS), and collect instrument monitoring data. Short optical fibers from the positioners will be routed to the back of the focal plane where they will be imaged by the Fiber Photometry Camera (FPC) or back-illuminated by a LED system. Target objects will be identified relative to guide stars, and using the GFA in a control loop with the ICS/TCS system, the guide stars will remain stable on pre-identified GFA pixels. The fiber positioners will then be commanded to the target locations and placed on the targets iteratively, using the FVC to centroid on back-illuminated fibers and fiducials to make corrective delta motions. When the positioners are aligned with the targets on-sky, the FPC will measure the intensities from the positioners’ fibers which can then be dithered to look for intensity changes, indicating how well the fibers were initially positioned on target centers. The final goal is to operate ProtoDESI on the Mayall telescope for a 6-hour period during one night, successfully placing targets on the intended fibers for the duration of a typical DESI science exposure.

Paper Details

Date Published: 9 August 2016
PDF: 9 pages
Proc. SPIE 9908, Ground-based and Airborne Instrumentation for Astronomy VI, 99087X (9 August 2016); doi: 10.1117/12.2231760
Show Author Affiliations
Parker Fagrelius, Lawrence Berkeley National Lab. (United States)
Charles Baltay, Yale Univ. (United States)
Christopher Bebek, Lawrence Berkeley National Lab. (United States)
Robert Besuner, Univ. of California, Berkeley (United States)
Francisco J. Castander, Institut de Ciències de l'Espai (Spain)
Institut d'Estudis Espaciales de Catalunya (Spain)
Arjun Dey, National Optical Astronomy Observatory (United States)
Elizabeth Buckley-Geer, Fermi National Accelerator Lab. (United States)
Ann Elliott, The Ohio State Univ. (United States)
William Emmet, Yale Univ. (United States)
Brenna Flaugher, Fermi National Accelerator Lab. (United States)
Irena Gershkovich, Univ. of Michigan (United States)
Klaus Honscheid, The Ohio State Univ. (United States)
Dick Joyce, National Optical Astronomy Observatory (United States)
Stephen Kent, Fermi National Accelerator Lab. (United States)
Robert Marshall, National Optical Astronomy Observatory (United States)
Ronald Probst, National Optical Astronomy Observatory (United States)
David Rabinowitz, Yale Univ. (United States)
Kevin Reil, SLAC National Accelerator Lab. (United States)
David Schlegel, Lawrence Berkeley National Lab. (United States)
Michael Schubnell, Univ. of Michigan (United States)
Santiago Serrano, Institut d'Estudis Espaciales de Catalunya (Spain)
Institut d'Estudis Espaciales de Catalunya (Spain)
Joseph Silber, Lawrence Berkeley National Lab. (United States)
David Sprayberry, National Optical Astronomy Observatory (United States)
Greg Tarle, Univ. of Michigan (United States)


Published in SPIE Proceedings Vol. 9908:
Ground-based and Airborne Instrumentation for Astronomy VI
Christopher J. Evans; Luc Simard; Hideki Takami, Editor(s)

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