Focal ratio degradation performance of fiber positioning technology used in the Dark Energy Spectroscopic Instrument (DESI)

Claire L. Poppett; Jerry Edelstein; Robert Besuner; Joseph H. Silber

doi:10.1117/12.2054454

28 July 2014 Focal ratio degradation performance of fiber positioning technology used in the Dark Energy Spectroscopic Instrument (DESI)

Claire L. Poppett, Jerry Edelstein, Robert Besuner, Joseph H. Silber

Author Affiliations +

Proceedings Volume 9147, Ground-based and Airborne Instrumentation for Astronomy V; 914763 (2014) https://doi.org/10.1117/12.2054454
Event: SPIE Astronomical Telescopes + Instrumentation, 2014, Montréal, Quebec, Canada

Abstract

The Dark Energy Spectroscopic Instrument (DESI) is a Stage IV ground-based dark energy experiment and will be used to conduct a five year survey covering 14,000 deg² to z=3.5. This survey is accomplished using five thousand robotically positioned optical fibers that can be quickly reconfigured with a 5 μm positioning accuracy. The fiber performance in the near and far field of two types of robotic positioners are currently being investigated: tilting spine mechanical simulators and eccentric axis (or θ-φ) positioners. The far field performance of the fiber is important since the instrument efficiency is adversely affected if light from the fibers enters the spectrograph at a faster focal ratio than the spectrograph can accept (f/3.57 in the DESI design). This degradation of the focal ratio of light is caused by light entering the fiber off axis (tiliting positioner) or bending, twisting, and stress of the fiber (eccentric axis) positioner. The stability of the near field intensity distribution of the fiber is important since this determines the spectrograph point spread function (PSF). If the PSF changes from the calibration to the science exposures, this will result in an extraction bias. For DESI, a particular concern is the distortions in the PSF due to movement of the fibers during re-pointing.

Citation Download Citation

Claire L. Poppett, Jerry Edelstein, Robert Besuner, and Joseph H. Silber "Focal ratio degradation performance of fiber positioning technology used in the Dark Energy Spectroscopic Instrument (DESI)", Proc. SPIE 9147, Ground-based and Airborne Instrumentation for Astronomy V, 914763 (28 July 2014); https://doi.org/10.1117/12.2054454

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available